EQUIPMENT FORUMS >> ZMA >> ZMA - comperhensive upgrade complete

Message started by bandrade on 04/04/19 at 23:29:33

Title: ZMA - comperhensive upgrade complete
Post by bandrade on 04/04/19 at 23:29:33

Building on the ZMA upgrades previously done by others on this forum (Vyokyong, Jeff of A and various musings from Steve Deckert), I ventured on a comprehensive ZMA upgrade program myself. It turned out to be a two year project. In previous posts I mentioned some of my earlier works on the ZMA and CSP3 and went silent for a while, while the upgrade process continued. Here is a comprehensive outline in one place starting from scratch for the ZMA. Observations on how the new parts affected the outcome and costs are included.

The objective of the upgrade process was essentially to leave Steve’s original design unchanged, it being proven and undoubtedly good but to upgrade each and every individual part. From a careful study of the internals in the original ZMA I concluded that Steve used parts of a reasonable quality every where, with key areas being treated with better/above average parts as an option (e.g. Type II Jupiter caps etc.). Since he has a business to run, this entirely makes sense to keep the price down thus allowing many more to enjoy these amps. I conclude from this experience that from the base original amp any upgrade is a case of diminishing returns, but for those willing to spend there are returns no doubt  and all these small returns add up for a impressive gain in the end at a price. In my case the total expenditure was about $4000 ( I did it all myself). It would perhaps work out to about $6000 if done by a technician as the number of hours spent was easily about 100 hours over two years. It takes considerably more time to upgrade than to build a new amp from scratch (once a prototype or design is completed).

Coming back to the upgrade for the most part I did a simple one by one replacement of (almost) all components in my ZMA with parts of the same specs as the original ones but of substantially higher quality. i.e. same capacitance or resistance but made of better quality material. Some new components costs were perhaps 2 to 25 times the original components. It might surprise you that in spite of the accomplished sound produced by the factory ZMA some of the resistors within can be bought for as little as 50c and up. Each of my resistors are now $6 to $50 and since there are very many of them it adds up both in price and final quality. Because price alone does not guarantee quality a lot of research and experience from others on this forum and other forums was considered before buying the parts. But good quality also cost more as there is no such thing as free lunch. The trick is to separate the hype from actual good quality, so in buying the various parts I was not so much concerned about the make and manufacturer of parts and the subtle differences between manufactures but leaned more towards upgrades of material and technology say from electrolytic or metalized film caps to copper foil and from copper foil to silver foil capacitors and from ceramic to non-inductive wire wound resistors and so on and then ventured to find a reputed manufacturer who sold these upgraded material parts at the best price. This was to weed out paying exorbitant sums for brand name and hype alone.

As I said before the whole enhancement process took me about two years as it was done one or two parts at a time. Most of the time went towards the research associated with each new part purchase and to allow for distribution of the costs over time. Time was needed as well to judge if the just replaced component(s) had indeed contributed to improvement - after adequate burn in. Only in one instance I had to reverse my upgrade and seek another component. Encouraged by each success (most times only incremental improvements were noted after each part change for quite a substantial cumulative gain described towards the end of this write-up), I have now come at a point where about 95% of the parts have been upgraded, the only constant being the original design.

Overall outline of what was done with details of each following:
•      Internal power supply path upgrade
•      Internal Power noise filtering upgrade
•      Bias current path upgrade
•      Input signal path upgrade
•      Amplification stage upgrade
•      Output signal path upgrade
•      Start-up/Shut-down enhancements (Bleed resistor modifications)
•      B - bus upgrade
Internal power supply path upgrade:
-      The original non-branded IEC female connector was replaced with Furutech IEC inlet FI-03 (R) Rhodium plated connector ($27). This resulted in the grip and fit with the male connector from the power cord to be significantly better. Additionally there is now better electrical conduction due to its pure copper prongs and more robust internal conductors for the fuse clamps.
-      Synergistic Research Blue Fuse ($150)
-      FURUTECH AC Cable FP-TCS31 Alpha ($157/meter) 12 gauge wire installed between the above new IEC connector to the power toggle switch replacing the original 14 gauge wire.  
-      Much as I would have liked to have changed the power switch, the original one was left in as I could not find a better one that exactly fitted in the slot.
-      The original generic full wave rectifier diodes were replaced with Schottky Ultra Fast 10A 1200V diodes ($110). These diodes cost more than 20 time the original ones but are worth it (see below for how they contributed to improvement).
-      Mundorf Mlytic 4700 uF HP+ 4 pole low ESL/ESR capacitors ($550) replaced the large red Mallory 2000 uF power capacitors. Note here that just because there are large capacitors in the power supply it (the capacity) is of less consequence if that stored power cannot be readily and fluently delivered when needed by the downstream circuitry i.e. delivered without transient dips in supply voltage and current due to lack of charge/discharge speed. High ESR/ESL caps than act as a choke point (in spite of the high capacitance value) due to their slower charge and discharge time constants.
-      Additional 47 uF and 1uF silver foil and copper foil capacitors ($300) added to the 4 poles of the 4700 uF Mlytic caps to more readily absorb the 120 Hz diode switching noise and to additionally speed up the power supply delivery. (The idea being that these faster smaller metal foil caps provide for the first micro seconds of power delivery when the music instantaneously demands it and then the slower larger electrolytic 4700 uF Mundorf Mlytic caps take over supplying bulk power minimizing the dips (minimize current ripple). BTW though I said “slower”, the Mundorf Mlytics by themselves are quite a bit faster than the original large Mallory red caps. The only thing going for the Mallory red caps is I believe that they will last 20 to 30 years where as the Mundorf Mlytics HP+ will last about 10-15 years. But these are very easy to change – no soldering required while the benefits in the meantime are enormous.
These 3 upgrades together (Schottky Ultra Fast diodes, Mundorf Mlytic 4 pole caps paralleled with fast copper/silver film caps) resulted in a step discernible overall top to bottom, side to side improvement: significantly reducing background noise and was just the tonic my speakers needed; especially the woofers – it was an ah! moment. A jump in overall performance was noticed right away on power up without the additional benefits that comes with adequate burn in – bass improvements (cleaner, tighter and deeper – brought the drums in the room) being the most significant, but also in the midrange and the high frequencies areas.
-      Wires connecting the Mlytics caps from the rectifier and also those to the regulator tube (RCA OA3) anodes were upgraded to Furutech POCC 14 gauge wire.
What I like about this is that the results were not only felt but also measurable. There is 3 to 4 dB gain from the woofers, 2 to 3 dB gain from the mid-range drivers and 2 - 3 db from the tweeters drivers with the dB meter placed 2 inches from each driver (all other settings and music played being the same), background also got way blacker and everything is more relaxed, less labored, fluent and natural.
Power supply is the key to improving everything else downstream – the sine qua non, the without which not.

Internal Power noise filtering upgrade:
-      The 4 x 47uF F&T capacitors on the ground rail (- B rail replaced) with 4 x Mundorf 47uF 500Vdc MLytic HV ($52).
-      These were additionally by-passed with 10 uF and 0.1 uF Obligatto Ultra Premium Gold film caps ($100) to remove a larger spectrum of power supply noise.

In theory these upgrades will reduce background noise further. In my case the improvement was not much, in fact hard to notice. Perhaps because by this time my power supply - both internal within the amp as described earlier and externally - was already clean and fast. Perhaps the laws of diminishing returns were kicking in. I experimented with disconnecting and reconnecting the by-pass caps (on one side) there was a sense that noise floor got lowered when these caps were connected but so imperceptibly that it could be psychological. I would imagine that for those in areas where the grid electricity supply has noise or without a dedicated power circuit in the house for audio and with no power conditioning equipment, it would make more of a difference.

Next … Bias current path upgrade and more

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/05/19 at 21:34:22

Bias current path upgrade:
-      Wires from each Bias Level pots (A6/B6) to the Balance Control pots upgraded with Furutech POOC 18 gauge double wires.
-      All resistors from the bias level pots to the – B rail replaced with equivalent resistance quieter and way larger 12W Mills resistors MRA-12 Series ($50). Original resistors vary from 0.5W to 2W (I think).
-      The Bias Level pots were not changed.
-      The Balance Control pots however were replaced with Audio Note 100K Ohm Stereo Balance Potentiometer ($160).
-      All resistors from the new Audio Note balance pots to the – B bus replaced with 12W Mills resistors MRA-12 Series ($80).
-      The 4 100mA ammeter 0.5 W resistors were replaced with 12W Mills resistors MRA-12 Series ($28).
I have now become a huge believer in far exceeding the wattage of resistors to 10 to 20 times the required steady state current handling capability and using non-inductive wire wounds ones. As music is not steady state but highly dynamic the larger wattage resistors and being wire wound (versus ceramic) allows faster unimpeded transient rise and fall of current. i.e. music dictates the current dynamics versus equipment dictating it due to its shortcomings. Like water flowing thorough a pipe. While a smaller pipe let’s say allows a varying flow of water (music) to fill in a bucket in y seconds, a larger diameter pipe will fill it in less than y seconds, since when the flow exceeds the full-bore capacity of the small diameter pipe it constrict the flow only allowing unimpeded flow when it is low. The rise and fall of flow (music) is affected. Hence timing is affected. Every time I changed a bunch of resistors – here and elsewhere - with larger higher wattage wire wound ones, it resulted in making the music more and more “effortless”, timing felt more and more spot on. It’s as if the original smaller ceramic resistors though very much capable of handling the power passing though them were constricting dynamics – the instantaneous rise and fall of current and thus affecting timing. And timing and rhythm is everything in music.
Besides hearing the improvements there was also physical proof: the 4 ammeter needles hunting reduced by as much as - hold your breadth - 80% even 90% !!! They are now almost steady when played at the same higher volumes. This less hunting indicates that when music is demanding power from the new power supply system (within the ZMA) it more readily supplies it without causing transient dips in circuit/voltage. It’s like trying to accelerate a low horse power car (before power supply upgrade) there is that initial hesitation followed by acceleration versus say a higher series BMW (Mundorf Mlytics 4 pole caps and parallel film power caps) which just seamlessly accelerates on demand without hesitation.

Next:.... Input signal path upgrades

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/05/19 at 21:44:20

Input signal path upgrades:
-      The original solid brass RCA connectors were replaced with WBT 0210-AgMs pure silver RCA jacks ($650 – ouch!)
-      Master Volume stepped attenuator bypassed since I control the volume at the source (DAC). The less the attenuators in the signal path from the source equipment to and within the amp the better. These attenuators are the single largest drag on the sensitive and delicate input signals. If parts of your input signal coming from the source gets stripped those parts cannot be amplified further down the line in the circuitry. Once lost its gone, the downstream ZMA amplification stages cannot amplifier lost signal fractions. Besides due to the law of conservation of energy I think that loss is converted to heat and noise in the circuitry. No point in having high grade interconnects and speaker cables if there are multiple choke points (attenuators, low wattage resistors, slow caps) within the signal path internally. The weakest point in your whole chain from source to speakers including internal circuitry in the amp, pre-amp and source equipment will manifest itself in the music you hear i.e. the weakest point dictates the sound. That means that one weak point in the chain will restrain the rest of your high end expensive system.
Of all the upgrades done by me, bypassing the attenuator gave the best bang for the buck. Almost a free one, only labor cost. If your overall system allows it get rid of unnecessary attenuators or simply bypass them so that you can go back, in the future if your system changes and you need one (at least one attenuator is required). Note that you will need a 80 to 100 ohm resistor connected to ground to maintain input impedance so that your source can more easily drive the amp without the source overheating.
Signals coming from the source through the interconnects and RCAs connectors now go directly to the input tubes (A12/B12) bypassing the master volume control. I used multiple ultra pure silver (6N) lintz construction tone arm silver wires ($400). In short the signal path now is DAC >>> Silver WBT RCAs >>> to 6N silver lintz construction wires internally >>> input tube (no attenuator in between)

This combination of upgrades brought out qualities in music that I listened to for years that I did not know existed. Familiar voices are far more clear and have more character e.g. the drawing in and out of the singers breath and subtle vibratos in the singer voice that were not apparent before appeared, pitch has more range, tone more authentic – life like. String instrument leading and especially trailing reverberations continue longer as in reality. Finger rubs on strings, hollowness of drums and reverberations of the drum diaphragm showed up in one case when they were not so apparent before. These accompanying natural phenomena make you believe that live music was being played within the room just in front of you. Sound stage improved significantly. Even whiskey and beer is more enjoyable while listening to music now.

Next ….. Amplification stage upgrade

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/06/19 at 20:32:57

A picture might be in order at this point given all the writing.

This one was taken at almost the last stage. As can be seen the internal space is now almost completely occupied due mostly to the larger resistor size and larger size of film capacitors compared to electrolytic capacitors of the same resistance and capacitance respectively. It was challenging to install these large parts in the original space and hence the capacitors and resistors had to have longer leads which is not ideal as these longer leads change ESR/ESL values a little bit. Also it was hard to make it look nice and symmetrical and parts physically parallel to each other.

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/06/19 at 20:45:53

This picture shows the Mundorf Mlytic 4700 uF HP+ 4 pole low ESL/ESR capacitors on the left and the large red Mallory 2000 uF power capacitors on the right.

The Mundorfs are shorter in height though have more than 2 times the capacitance compared to that of the Mallory caps.

I did a comparison of the sound on the left channel (Mundorf) to that of the right (Mallory). The gains in db on the left side was about 3 dB for woofers and slightly lower gains for the midrange and tweeters. This test was with only the one left Mundorf  Mlytic 4700 uF HP+ 4 pole capacitor replacing the left red Mallory's all else remained the same.

Title: Re: ZMA - comperhensive upgrade complete
Post by Jeff of Arabica on 04/07/19 at 06:52:02

Damn Bonny!!  That is one pimped out ZMA!  I just wish I was within reach of you so that I can hear what she sounds like.  You certainly took whatever inspiration you gained from Steve, me and Vyonkyong and raised the bar astronomically.  

I really enjoyed reading all the additional modifications you completed beyond what you and I had discussed prior.  There is no doubt in my mind that you have the best sounding ZMA in existence.  I will of course proclaim the second best sounding ZMA   ;)  

I removed my attenuator and added a Tortuga Audio Light Dependent Resistor (LDR) passive pre-amp for attenuation which has adjustable impedeance from 1K-99K Ohm so I did not have to add a resistor to ground when I pulled the attenuator from my ZMA.  

This is all way too much much, isn't it!  

Title: Re: ZMA - comperhensive upgrade complete
Post by HockessinKid on 04/07/19 at 12:48:43

Wow, thanks for sharing all the details of your extensive modifications. Truly an exceptional level of changes, thanks for sharing with us. As Jeff said, definitely the best sounding ZMA bar none. Hope you are enjoying it immensely.

So in addition to Steve's ZMA 25th Anniversary mods, what would you say are the three "relatively simple" additional changes you could recommend to other ZMA owners to improve their amps sound quality? Or in other words, what were the changes you made that resulted in the biggest improvement in sound quality?

This might provide insight for DIY'ers and/or future modification packages Decware might consider.  Thanks.


Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/07/19 at 16:11:53

Jeff and HK, thank you for your feedback.

Jeff your LDR - I think - in fact is a better way of doing it obviating the need for a fixed resistor to ground. By having a fixed resistor of between 60 to 100 ohm one is guessing as to the best value based on sound and temperature of source internals. Whereas since you are able to adjust the resistance infinitely it is more precise and the flexibility allows you to change your source and be compatible still. The only small down side would be that there is another set of interconnects and RCA connectors in the way.

HK, it's my pleasure giving back to the Decware community having been given the initial impetus by them. Each upgrade that I did had it's contribution in incremental steps, but if you are not going the whole hog I would consider these three in order of priority:
- Bypass attenuators if your system allows for it. You will hear additional nuances not heard before. Best bang for the buck by far as it cost nothing, just labor time/charges.
- Replace the solid brass RCA input connectors with high purity copper or silver one. Again you will hear additional nuances not heard before.
- Power cap upgrade to faster caps. (I know you asked for 3 outside of Steve’s 25th anniversary mods – I want to bring on the benefits of 4 pole caps will additionally lower noise while lowering ESL/ESR values. This will increase the amp’s ability to drive lower efficiency but higher quality (frequency range) speakers. I feel the word "efficiency" in terms of speakers is a misnomer. It just tells you that your speakers can be driven by lower wattage amps but does not tell you of the quality of sound and the ability to reproduce sound covering a large extent of 20 Hz to 20,000 Hz and beyond both in either direction. Over the years I have come to believe that even if one’s ability to consciously hear is only in the middle portion of that range it is important for the equipment to reproduce it all of it and beyond as it does affect the propagation of sound and hence perception of it. Hence supertweeters have an effect on music, but that is another whole topic as to why.

Also note that when things are done more comprehensively each upgrade seems to make all the earlier upgrades work even better. Like a symbiotic effect.


Title: Re: ZMA - comperhensive upgrade complete
Post by HockessinKid on 04/07/19 at 16:46:35


Thank you again for sharing and your thoughtful suggestions. Since I will be sending in my ZMA for 25th Anniversary mods next month, I'll request some additional modifications per your suggestions.

I have a CSP3 preamp, ZROCK2 and ZDAC, so three sources to control volume and ride the gain.

Removing the attenuator makes sense, I almost had this done to on my original build, so I'll add this.

I'll also get the RCA input jacks replaced. Having heard the benefits of WBT RCA terminations on some of my ZenWave IC's this also makes sense. I believe Parts Connexion and/or VH Audio have some of the WBT Nextgen models on sale.

Regarding power caps, I believe Steve includes the option of replacing standard caps with new Nichicon NX 4700's. Are these the type of caps you were referring to? I know you selected Mundorf caps, but these are pretty expensive and I prefer the 20 year lifespan, unless there is a significant SQ difference between the two.

Feel free to share any additional thoughts or suggestions. Also, does replacing the power IEC input make much of a change? My power cord is pretty heavy.


Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/07/19 at 18:52:36


The Nichicon NX that Steve is using in his 25th anniversary mods are I think 3300 uF, 2 pole caps. I have not researched them enough to talk about them at great length but Steve from his writings has experimented with various 2 pole caps and likes them so they should be better than the original ones. Mind you Steve's objectives are constrained by having to run a business and making the upgrade affordable to a larger audience and rightly so as it is in all our interest that he keeps his business running. As well to fulfill the life time warranty promise he has to make decisions differently. It’s not hard to see that these objective might compete with absolute quality being the overriding factor. My feeling is that while the Nichicon’s are better than the red Mallory's but they are not as good as the Mundorf Mlytic 4700 uF HP+ 4 pole which being 4 pole are more difficult to construct. In my decision making, I try to find if the claim is supported by theory. That way I can separate hype from fact. If science supports what is said that means it is not woodoo magic that produces the improvement. 4 pole caps use all of the positive and negative plate surface area and the dielectric between them. With 2 pole caps – especially larger ones there will be internal preferential pathways (due to impurities/inconsistencies in the dielectric - remember these are not ISO-9000 certified companies) instead of the complete internal volume (i.e. plate and dielectric) being used for useful purposes. As caps get smaller this benefit reduces so 2 poles are OK for smaller caps.

To your IEC connector query: I would recommend replacing the IEC connector. I closely examined the Furutech connector I bought with the original one and can tell you that even forgetting the material quality (copper v/s brass) the construction of conductors is at least twice as robust. The price for the Furutech IEC connector is less than $30.

Hope the above is of help.


Title: Re: ZMA - comperhensive upgrade complete
Post by HockessinKid on 04/07/19 at 19:29:31

Thanks Bonny

Can you provide a source for purchasing the Mundorf Myltic 4700 uF caps and the Mundorf catalog item number if possible. It appears Sonic Craft only carries up to 3300 uF caps and HiFi Collective is currently out of stock.

Are these difficult to install myself? Is aditional wiring/soldering required?  I believe they have screw terminals.

Apologies for all the questions but I want to get it right.


Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/07/19 at 20:34:05

HK, not a problem. It is not very difficult to do but changing for two pole to 4 pole will require some wire reconfiguration which requires a little bit of soldering to lengthen and separate existing wire. Once done it is a drop in fit the next time it needs to be replaced, only a screwdriver will be required.

Beware though, if you want to keep your warranty ask Steve if he is willing to do it for you. If I remember right he had posted after I had done mine that he prefers a max of 3300 uF that he did not want to go to 4700 uF though he said that 4700 uF is the max one should go to. At that time I was so impressed with the outcome of this change of going to the Mundorfs 4700 uF that I had posted that I would like to go higher. He cautioned not to go higher and I did not. This is to do with life time warranty I would think. While performance will increase but as you go higher in capacitance the internal voltage remains high due to there being less of a drop in voltage and so you are pushing it closer to its limit (note you will never exceed the voltage limit as it is governed by the input transformer) instead of operating well within its limit with reserve as a cushion, so the life span decreases from say 25 – 30 years to 10 – 15 years. For me it is better have higher performance now and change those caps when the time comes as I am OK with 15 years of service before changing again.

It would be best to try to find a 3300 uF 4 pole cap and ask Steve to do it for you as he is comfortable with 3300 uF and keep the warranty.

I got mine from Germany through ebay. I'll trace back and get back to you with the details. I remember there were not many of them and so it was hard to get them as Jeff of A had done it before me, so based on his feedback I started looking for them since it made sense.

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/07/19 at 20:39:05

Here is a picture of my ZMA taken before this process began 2 years ago for comparison.

Title: Re: ZMA - comperhensive upgrade complete
Post by HockessinKid on 04/07/19 at 20:40:52

Got it, good advice. I'll check in with Steve about substituting the Mundorf 3300uF caps having him do the work. Thanks.


Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/07/19 at 21:01:23

The seller I bought from in Germany has no 4700 uF Mlytic caps  currently.

But he has 3300 uF Mlytic caps.

I found another listing from France. The price is quite good as it is a unused resale. Seems like it is 60% after customs duty and shipping of what I paid back then.

Title: Re: ZMA - comperhensive upgrade complete
Post by JD on 04/07/19 at 21:27:55

Fantastic work. Envious skill set you have, thanks for explaining everything in a way that was accessible.


Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/08/19 at 00:53:08

Continuing on ….

Amplification stage upgrade:
-      All resistors to and from the input and inverter tubes replaced with either low noise 2W Audio Note resistors ($150) or 12W Mills resistors ($150) e.g. 330ohm output tube grid resistors with 2W versions of the Audio Note resistors replacing 0.5W original resistors.
-      Signal capacitors replaced with 0.1uF 600Vdc Jupiter Copper Foil ($126) and Jupiter 0.022uF 600Vdc Copper Foil ($76) capacitors
-      Additional parallel 0.01uF Duelund copper foil capacitors ($150) added across the above signal capacitors.

Output signal path upgrade:
-      All resistors to and from the output tubes replaced with 12W Mills Resistor MRA-12 Series ($100). Originals were 2W or less.
-      A 12W Mills resistor of 330 ohms added between the screen grid pin and Ultra linear tap of the output transformer based on Steve’s 25th anniversary mod. Here I had to do a few reversals, experimented with 220 ohms, 480 ohms finally settling with 330 ohm.
-      Original solid brass speaker binding post replaced with WBT 703 pure silver ones ($700 – again ouch!).
-      Furutech POOC 12 gauge wires added to the negative speaker binding post to – B bus.

Of all of the above, the speaker binding post change to WBT silver ones was the distinguishable one in that it further enhanced the experiences outlined in the last paragraph of the input signal path upgrade.
Where as for the other upgrades listed here they enabled lower level listening without loss of micro detail. This was a nice experience (kind of a ah! moment on experiencing this fact) as it suited my listening behavior better since I prefer low level listening most of the time with the occasional high volume play when in the mood. Having said that to entirely attribute this phase of upgrades to the ability to listen at a lower volume may not be totally correct as I am sure all of the other stages helped as well in that if the other stages were not done this low level listening experience would not be possible.

Next .... Power on/ off enhancements - bleed resistor upgrade

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/08/19 at 23:41:47

JD, thanks for your feedback. Glad you find it useful, that is the idea so that more folks benefit from my experience, perhaps even Steve might want to increase the upgrade options he offers.

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/09/19 at 01:12:13

Power on/ off enhancements - bleed resistor upgrade:
-      Replaced the original single 220 Kilo ohm resistors per side with 330 Kilo ohm (3 parallel 1 mega ohm 5 W resistors in parallel to create more flow paths) resistors per side.

These resistors are there so that when the power is switched off the large power capacitors and all other caps in the circuitry can smoothly discharge their residual stored power to ground. The down side is that during operation they lower the overall circuit voltage and will introduce noise into the –B rail. This noise backwashes into the signal path as the returns of both the power supply and signal circuit are connected to this same return rail (more on minimizing this later).

As you can see I increased the bleed resistor resistance slightly from 220 kilo ohm to 330 kilo ohm to minimizes parasitic power losses during operation. In turn this will reduce overall circuit voltage drop. So more power is now being used instead of wasted. Because voltage drop is reduced it in turn will reduce the current drawn by the various in the internal circuits for the same power output (P=V x I) which in turn reduces heating of internal components (Q=I2 x R) for the same power output. This is waste heat i.e. power that is not being utilized.

When power is now turned on the OA3 regulator tubes do not make any sound at all and achieved steady conduction state status within 5 to 6 seconds vs about 9 to 10 seconds earlier. The ammeter needles now start ramping up a few seconds earlier and achieve their steady state value a few seconds faster. On powering off the OA3 tubes stay lit for about 3 seconds before flickering off with less flickers than before. The ammeter needles oscillate and deflect a lot less. These needles used to oscillate and deflect almost full scale earlier when power was turned off. With PSvane KT88 tubes in and biased at 70 mA one of the ammeters would get pinned to the extreme end on turning power off. A tap on the ammeter glass would bring it back (this was the reason I thought of slightly upping the resistance of the bleed resistors which in turn helped in other ways as listed in the paragraph above). Now the needles deflect  about 90 percent of full scale on powering off and come back on their own. Important to note that this pinning of the needle was not happening on the original un-modded amp it started after I did some of the upgrades. I attribute it to more energy being stored in the additional bypass/parallel caps and higher capacity power caps installation besides steps were taken to lessen the wastage of power as mentioned earlier. BTW I have long since moved on to Tung-Sol 7581A's and Black Boxed anode triple mica 6N5P's and bias at 58 mA.

Next ….. -B bus upgrade ….. the last one ...….. after which I'll summarize the overall cumulative effect.

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/10/19 at 22:10:55

B - bus upgrade:
I added additional Duelund 5N silver wires from each of the connections to the B - rail (cathode bias current returns, power supply filer caps, input transformer connections, level and balance pot connections, speaker binding post etc.) going directly to the exit point on the B - rail making it a multi rail design. Since these circuit connections have different voltages and currents the current flow is not necessarily entirely to the intended exit point but could partially re-enter back into main circuitry. These various currents would flow in directions according to Kirchhoff’s current and voltage laws for junctions. So noise and parasitic currents could stray backwards into the circuitry affecting the design intent of these individual circuits. Even with the multi rail system there is ultimately a common point so there is mixing and congestion at that point but much less than a single rail system.

All soldering was done with WBT 4% silver solder - one and a quarter spool used in all!

That concludes the work done to upgrade the ZMA.

Next .... overall conclusion and thoughts

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/11/19 at 00:22:46

Overall conclusion:
The overall result is simply sublime. A fantastic original amp in its own right got exponentially better. Listening at all volume levels - high and low volume - got better. The question is, is it worth the $4000 or so spent? that would depend on each person, for me it is given that it’s now going to be enjoyed for the next 2 decades or thereabouts. When I first bought the ZMA (with all original upgrade options) I thought this was it. After the initial euphoria settled, I realized at lower and at higher volumes I did not feel as satisfied as when listening at mid volume levels on my system. My PSB T3 speakers are 89 dB efficient (91 dB anechoic) but capable of going down to 24 Hz and up to 22 kHz. The alternative was to buy very high efficiency speakers but I have listened to some and though impressed the lack of deep bass at the one end and sparkle at the other when playing music that has those elements did not satisfy as much. High efficiency speakers I found were excellent for a vast range of music but not all. Admittedly I did not try out very many of them so I could be wrong.

Here is another fact that demonstrates the usefulness of these upgrades done by me. Initially I was compelled to bi-amp the PSB T3 speakers with the unmodified ZMA driving the tweeters and mid-range drivers and a Solid state Cary Audio amp driving the woofers and TakeT Batmaster super tweeters (reason being the Cary audio went down to 18 Hz and up to 90 kHz (-3 dB) as tested on my audio analyzer while the ZMAs range was 28 Hz to 52 kHz). The unmodified ZMA would start clipping at mid-volume levels if it was used to drive the T3s on its own (not bi-amped). After the upgrades with the ZMA alone I now drive the T3 at beyond mid-levels into the lower high volume levels before clipping becomes apparent.

As I mentioned earlier the returns are diminishing from the base factory amp. As can be seen one has to spend a bit to go to the next level. My experience is that changing a part here and there will improve things for you but not to the level that takes your music a quantum step up in level. The rest of the circuit still acts as a chock point not allowing that upgraded part to bloom to its full potential. From my experience I can say that each upgrade makes the previous upgrades better and the previous upgrades made the most recent one better as more and more weak links are removed. Until all is done it is a wandering weak link (another old part become the weak link) and then that weak link will define the quality of the music that is output.

My music listening experience now has that feel good factor one gets when listening to a live show in a quiet room (best of both worlds). Besides 3D imaging and spatial improvements, there is also what I now call the magical 4th dimension which to me is a complex concoction of timing, speed, dynamics, rhythm, density, separation of instruments, voice layering (foreground, background) all within that increased density, each distinct and more life like. Additional nuances in long familiar music have appeared. More over everything is more naturally reproduced with less strain and more perfectly placed in 3D space and time.

Future upgrade considerations:
I am suffering from upgrade fatigue and am going to take a long break and just enjoy the system now. In preparation for the future the only thing, I think that will make a further step jump in performance after all of the above will be an upgrade of the input and output transformers, especially the input transformer as it is a significant part of the source power. I am have trouble finding high quality ones which will seamlessly fit in the original space. If anyone has done this or has ideas it would be awesome if you could share it.

Well folks that’s it from me, hope some of you get inspired by this experience of mine. It is not so daunting money wise and effort wise if done over a period of time.

The end reward is worth it.


Title: Re: ZMA - comperhensive upgrade complete
Post by glineus on 04/11/19 at 01:25:35

Hi Bandrade,

Great Stuff, I admire your expertise. You can now relax and enjoy your ZMA comfortably for as long as you desire.

I am the owner of a TORII MK1V and I am fully aware that the Decware line of amplifiers has immeasurable potential. Who knows! Steve may one day offer these upgrades to owners who seek to unlock the potential of his masterpieces. ;D ;D


Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/20/19 at 00:39:14

I have been wrestling with solving the mystery of why a wholesale change to larger wattage resistors improved the dynamic response of my system.

Here is my half baked theory: larger wattage resistors (but of same value) have a lower RC/RL time constant (𝜏) so it helps in facilitating transient rise and ebb of current within the audio circuitry. The resistance value being the same the end voltage drop across the resistor is the same but it reaches this end value faster. Music being dynamic if the previous signal does not reach its peak before the next instance of signal it gets superimposed and so mis-represents the original signal affecting the outcome.

Feel free to chime in on this by agreeing or disagreeing with it or stating your own. It will help in understanding this phenomenon.

Because manufacturers do not test the intrinsic RC or RL time constant for resistors or at least state it in their specifications this is only a guess at this point. I have an idea of how to crudely test this theory. Will get back if I decide to go ahead with the test until then it is just a theory of why it works.

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/23/19 at 21:33:58

The question of fuses

When it comes to potential gains from a given upgrade I find upgrading amplifiers and source components and their components within as mentioned in earlier posts result in a more dramatic improvement than upgrading cables. But what about fuses? I see the fuse as an essential compnent from a safety point of view but restrictive from an audio point of view.

To me the fuse is the first major restriction any piece of audio equipment experiences. As many of you also mentioned else where I too find that the type of fuse used affects the outcome. However, I thought it would be more convincing to have objective electrical readings to confirm the influence of fuses. So I thought of devising an experiment to obtain concrete numbers that confirm or discard the notion that fuse quality matters and whether the notion that a fuse is a fuse is a fuse is right or wrong.  

Following is how I performed the experiment. I decided to test 2 types of fuses: a stock glass type and the SR blue fuse that I am currently using, each being at the opposite end of the scale from price point of view - $1 for the glass fuse to $150 for the SR Blue fuse. I also decided to test these against a 6 gauge bare copper wire in the fuse holder under controlled conditions (limited duration and being in constant attendance). For this test I’ll call this 6 gauge copper wire the 3rd fuse type. Each type of fuse was directly placed in the IEC fuse holder clamps without the fuse IEC fuse housing to enable readings of the voltage drop across the fuse to be taken while the amp was playing loud music just below clipping. The voltage drop was checked with an extremely sensitive multimeter.

Pictures will follow.

Here are the results:

Type of fuse                  Voltage drop in mV
Glass fuse                                    0.45 to 0.95 mV
SR Blue fuse                            0.16 to 0.55 mV
6 gauge bare copper wire              Rock solid 0.00 mV

You see a range of values in the chart above as the readings were fluctuating within that range. I attribute this to the dynamics of music as it was being played it was drawing larger and smaller amounts of current as needed.

As can be seen the SR Blue fuse appears to be able to supply 2 to 3 times more instantaneous power to the amp versus the glass fuse. But the bare copper wire with its rock solid 0 voltage drop on this sensitive multimeter capable of measuring more than 5 digits after the decimal point indicated that it is infinitely better than the SR Blue fuse. The 0 voltage drop suggest that the ZMA at its top power draw (almost clipping level) did not restrict the 6 gauge wire from conducting but the other fuses were somewhat restricting current, one more than the other.

So glass fuse <<<< SR Blue fuse <<<<<<<<<<<<<<<<<<< thick copper wire.

This simple experiment showed me that fuses are indeed a bottle neck and the type matters. I kind of expected it to be so but was surprised at the manifold difference between each type given that when listening I did not think the SR Blue fuse is 3 times better than the plain vanilla glass fuse. But than again what is 3 times? how do you measure sound quality in terms of numbers? As well it takes a lot to gain a little the higher one goes – the law of diminishing returns.

Most of us use thick expensive audiophile power cables. In series with this expensive audiophile cable at the IEC inlet is a very thin single strand wire fuse (or a ceramic fuse). To more hit home this fact, picture this: imagine that an inch of insulation length wise on the live (black/blue/red) wire of your very expensive low gauge power cord is stripped off somewhere in the middle and one inch lengths of all copper strands of that wire in that area is also removed keeping only one strand. This is exactly the situation in actuality, except that this single wire is at the end of the cable downstream of the IEC connector live (sometimes neutral) prong in the fuse. The above readings show that the fuse is a bottle neck though an essential one for safety (fire) reasons not audiophile reasons.

Note that these readings support electrical theory. Since electrical resistance is also dependent on the material (coeff. of electrical conductivity) and is proportional to the length of the conductor and temperature of the conductor and is inversely proportional to cross-sectional area of the wire, that single wire strand glass fuse being of a way smaller cross-sectional area compared to the power cable its resistance is way higher than that of the cable itself. But temperature being another factor that changes a conductors resistance it gets worse as that single strand heats up more than the actual cable due to I2R effects as current passes thorough it (confirmed by taking temperature readings of the cable itself and comparing it with that of the fuse) adding to the resistance.

This being the case and material being a variable, if that lone wire strand in a glass fuse was instead replaced with better material (SR Black or Blue fuse or IF Tuning Supreme or others each better or worse than the other as the case may be) allowing better conduction of electricity, it would help the cause of producing better quality music.

A word of caution if you ever dare to try (btw never leave sight of the amp in order to be able to turn if off at the slightest hint of trouble, as it is a huge fire hazard if left unattended if you do try it) the wire in fuse holder: My already very good system that I though would take a lot more time money and effort to get better after all the seemingly zillion upgrades I did, sounded quite a bit better with the inch 6 gauge high end bare copper wire (perhaps costing only $5) in place compared to even the SR Blue fuse. There is now a strong urge to leave it in. Conducting the experiment as I moved from the glass fuse to SR Blue fuse to bare copper wire I realised the following: Glass fuses stifle everything (had forgotten this fact until now as the last time I had a stock type glass fuse was 3 years ago). Having listened to music with the SR Blue fuse in for more than a year now putting in the glass fuse for this experiment was an eyeopener (should I say ear opener). Even so the copper wire “fuse” blew the SR Blue fuse out of the park allowing my system to reach stratospheric heights – micro-dynamics, detail, spatial representation and timing way, way better – there is no end to this madness. I have come to believe no matter where you are it can get even better.

Having tried the wire in place of the fuse I am now in a quandary: one part of me does not want to go back to the SR Blue fuse. Alas safety overrides everything else so I have gone back to the fuse but just knowing that my system sounds quite a bit better with a 6 gauge wire in the fuse slot is bugging me a lot, wishing I had not done this experiment ha! ha!

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/23/19 at 21:55:02

Glass fuse voltage drop reading. The voltage was fluctuating up and down between the 0.45 to 0.95 mV range due to I presume the dynamic nature of music and the fuses limitations. This is a snap shot somewhere in between in that range when the camera shutter opened.

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/23/19 at 22:00:20

SR Blue fuse under test. Had to reduce the quality of the picture due to enable posting due to size restrictions.

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/23/19 at 22:07:35

The humble copper wire reading. 0.0000 V drop! no matter how high I went even briefly tried going in the clipping range. See picture.

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 04/24/19 at 01:21:17

As can be seen the SR Blue fuse appears to be able to supply 2 to 3 times more instantaneous power to the amp versus the glass fuse.

Aren't you severely overstating the difference when it comes to voltage drop versus instantaneous power?  Yes, the glass fuse has 2 to 3 times the voltage drop but it's still a small number compared to the total voltage.  I'm not contesting the use of "better" fuses but the numbers aren't that impressive.  Now the 6 gage wire is very interesting.  I've never had a fuse blow so I don't really know how to evaluate risk but it seems low.  Except for the fact that despite low risk, consequences could be astronomical.

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/24/19 at 05:18:51

Archie, thank you for bringing this up, looking back my explanation was not clear because I took things for granted.

It seems like those readings in the millivolt region are insignificant but it depends on what it is about. Millivolt when it comes to power say a battery is indeed insignificant in fact very insignificant. I am not interested in voltage drop per say. A voltage drop of 0.95 millivolts on a 120 volt supply gives us  119.999905V which is absolutely OK and a waste of time writing about because our grid voltage fluctuates much more than that. But here we are trying to indirectly establish resistivity and here millivolt is significant. Any sort of voltage drop across a conductor especially across only an inch of a conductor, indicates it is not a pure conductor there is resistance in it compared to a pure conductor. That is why absolute audiophiles that have loads of money will buy power cables with 5N even 7N pure copper in it and even beyond going for 5N silver cables. If I did the same test between say a 5N copper cable versus a 7N copper cable I will need I am guessing a multimeter that is sensitive to 25 digits after the decimal. But audiophiles want every last bit of performance so they go for the 7N copper cable. It depends on what one is satisfied with and what one is willing to pay. Even with different material conductors the difference is not much in terms of voltage drop: say with a hypothetical mild steel cable versus a pure copper cable the voltage drop will be far less than a glass fuse versus SR Blue fuse but I would not want a mild steel cable powering my equipment. I have not tried it nor would I want to.
Having said that in terms of difference of readings between a glass fuse versus say a SR Blue fuse here I was interested in by how much of a factor is a glass fuse is worse than a SR Blue fuse and the factor is between 2 to 3 times worse. It is obvious both these fuse type still work and largely do their job, but I am talking about trying to extract performance way beyond the normal.

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 04/24/19 at 16:15:19

I really don't understand the finer points of things electrical but it is funny to think of the size and materials of our power cords and then to see how that same power then goes through a tiny filament of a fuse.  That's why the 6 gage wire is so interesting.

An assumption I'd like to challenge is the precision of some of these measurements.  I'm sure you weren't really serious about 25 places after the decimal but how far can it be accurately measured outside of a particle physics lab?  The "purity" of some of these cable's materials is also highly questionable.  I know slightly more about physical measuring and when machinists start talking in millionths, things get really squirrely!

I generally don't question when someone on this Forum says they hear something but I am always curious/suspect of the why.  Everytime someone (especially Steve) comes up with an improvement I pay attention but like many here, I can only afford or have enough interest to do some of what's presented.  I have a hard time understanding how a great sounding amp can sound "twice as good," for example.  This is just a general observation of terms of improvement that I often read on the Forum.

Back to the resistivity of a fuse, I still don't necessarily see how variations in a small number might be important.  An analogy might be in say, cancer rates where a study might demonstrate cutting the cancer rate in half (sounds HUGE) but if only 2 in a 10,000 get the cancer than now only 1 in 10,000 will.  But maybe resistivity is something completely different.  As I said, the finer points of electronics escape me.

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/24/19 at 22:01:26

You said "I generally don't question when someone on this Forum says they hear something but I am always curious/suspect of the why"

I must say I am the exact opposite, I sometimes wonder when well meaning folks say that so and so aspect has improved without backing it with measurements or science, I wonder if its rationalization (our brains are finicky) because that person has spent money on it, so wants to hear that improvement and the brain obliges. Where as measurements are a fact that does not depend on the brain’s subjectivity. Going by your statement above I figure you are skeptical of everything I said in all the of above posts because of my liberal dosage of science backing (the why) and measurments. Reluctantly I am forced to tell you why I take measurements where ever it is easily possible and back things by theory. I am an engineer (I am sure there a many more on this forum), when we talk among ourselves at trouble shoot sessions in a professional setting we always say "that which we cannot measure we cannot improve" so it is ingrained in me from my professional life being a daily habit for a few decades now.

You also said “I have a hard time understanding how a great sounding amp can sound "twice as good," for example”.

I do not deny that the ZMA is a good sounding amp. I mentioned it all along but have an issue with saying that it is the ultimate and cannot be improved any further. Not sure if you have costed most of the original parts (resistors, capacitors, solid state rectifiers, brass connectors etc.) in the ZMA, the parts within are of average (let me stress – not poor but average) quality. Only some capacitors are slightly above average included as an option. I have no issue with it as built, if I was running a business, I would perhaps do the same.These parts more than adequately do the job. It is the direct and straightforward circuitry that does the magic. I have largely not touched the circuitry just improved the parts and removed impediments like attenuators that I do not need in my audio system as a whole.

BTW I think you are right to question everything because I get the feeling that it is genuine and based on your experience and I respect it and have no issue with it, just giving you my side of it hopefully without causing you to feel I am challenging what you said. And off course it is obvious you do not have to spend money on something you do not believe in. I put the information out there for folks to benefit from my experience and together have a better experience as I have from some of them.  

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 04/25/19 at 01:05:46

I'm guessing a lot of us here are Engineers.

Some of what I wrote didn't pertain to your posts specifically and I don't doubt that you hear improvements, regardless of measurements.  Most of my deepest held convictions cannot be backed up by objective evidence.

The point I was trying to make was that I'm not sure whether the fuse numbers justify what you hear or not.  It could be due to other things you don't measure or can't.  Moreover, I was questioning whether those numbers were in fact as significant as you seemed to suggest.  Regardless, enough on this forum have reported improvements in sound with better fuses to make a believer out of me.  Sorry if I was nit-picking your science.  In any case, all of our engineering science is just a mathematical model of how we think things work.  The models are most often crude approximations and while perhaps the best we can do, are not all inclusive.  That's why often I trust, where trust seem justified, without "proof."

Title: Re: ZMA - comperhensive upgrade complete
Post by Donnie on 04/25/19 at 01:48:02

So my question is WHY?
Why not buy something different? Did you buy the amp for it's casework?
Is there something about the design that you like but don't think that the execution was good enough?
Maybe I don't understand because I'm not an engineer. I'm just paid to be one.

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/25/19 at 03:05:40

I first bought the ZMA due to the excellent feed back and was certainly not disappointed. Then reading about the improvements done by others and their experiences I took a peek inside which was a bad idea that cost me a small fortune. But from a satisfaction point of view was entirely worth it.

Title: Re: ZMA - comperhensive upgrade complete
Post by Jeff of Arabica on 04/25/19 at 05:55:51

From my personal experience with "modding" the ZMA, I can honestly say it is STILL A ZMA.  If you recall, I (and Vyonkyong before me)  actually installed a power supply bypass modification (amongst some other key component upgrades) before Steve created the Anniversary mods on the ZMA that are now offered from Decware.  

I think the answer to your question is simple...  Just like Steve believed that the ZMA topology had greater potential.  This motivated the R&D which later resulted in the current ZMA Anniversary additions. Bonny (and myself) embarked on a journey that took us down a slightly different path but ended up at the same destination - a much improved version of the ZMA that we loved then, and love even more now!!

Bonny has undoubtedly gone to the extreme but at the end of the day, Steve himself determined that the genius in his design could be bettered, just like all the amps he currently offers with the Decware Anniversary "mojo" sprinkled about.  

Lest not forget, a ZMA it was..  and a ZMA it still is.   It is Steve's creation and regardless of what "tweaks" are applied, the design credit was birthed by Steve (and I'm sure he has the stretch marks to prove it) and for that I am thankful.  

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 04/25/19 at 15:53:55

I hope bandrade takes his ZMA to Decfest this year.  It'd be great to get more impressions on how his ZMA compares to a "stock" ZMA -- but maybe one with the anniversary mods.

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/25/19 at 21:16:33

I live in Canada.

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/25/19 at 21:50:22

To Jeff of A’s point. Steve created the ZMA from scratch. That is infinitely more challenging than just replacing part for part where all values of resistors and capacitors are known. Steve had to come up with those values by swapping resistors and capacitors and what have you in and out hundreds of times in various permutations and combinations and take measurements on his high end oscilloscope and frequency analyzers and do the voicing to hit the sweet spot … infinitely more challenging …. and all this keeping the price point in mind all along so that the final product would be acceptable to his target buyers (my total price for the ZMA if upgrade by a technician will work out to be approaching $12,000 - less buyers at that price) making it an extremely difficult proposition to juggle everything. Not even close to just swapping parts as I did.

To use an analogy of an automobile, the manufacturer takes years designing and building a car from scratch and then installs standard tires (and other parts) on it that are acceptable as driven out of a dealership. Acceptable because of the reasonably good driving experience for the price point. Then some folks install better tires that make the ride smoother, less noisy at high speeds, help with less braking distance, better wet traction etc. Far easier to do swap tires to better ones because the tire size is already decided, but the ride is better and safer.

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 04/26/19 at 00:46:08

You can still come.  I don't think there are plans for a Northern Border wall ... yet.   :D

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 04/29/19 at 01:28:21

In terms of ease and practicality of the upgrades on a scale of 1 to 10 (in brackets) below is my experience - 10 being the hardest:

-      The large power capacitors (This is a 25th anniversary mod however, I (and Jeff of A) had done this prior to the 25th anniversary mods,  we shared our experiences connecting them in 2 pole configuration and 4 pole configuration. 4 pole connection results were excellent and also resulted in lower noise floor (2)

-      Installing fast smaller copper and silver film capacitors in parallel with the large power capacitors to reduce power supply response time during spikes in power demand as music is being played and flatten the power supply output (i.e. reduce ripple) further (3).

-      Furutech IEC connector (4).

-      Solid brass speaker binding post change to pure silver WBT ones (6).

-      Solid brass RCA connectors change to pure silver WBT ones (4).

-      Ultra pure silver litz construction wire for signal wiring from the RCA connectors to the input tubes (4).

-      Bypassing the attenuator (4).

-      Balance Potentiometers replacement with Audio Note ones (7).

-      Bleed resistor value change (6).

-      Bypass capacitors on the B – rail (This is a 25th anniversary mod but again, I had done this before the 25th anniversary mods) (3).

-      Screen resistors on the Ultra-linear taps of the output tubes (this is a 25th anniversary mod and  was picked up from Steve. Was essential in taming and fine tuning the ultra sharp response the other upgrades brought about) (4)

-      Copper foil signal capacitors (4)

-      Furuthech POCC wires in power supply area (3)

-      Full wave Rectifier upgrade to ultra fast low loss, less (near zero) overshoot ones (7)

-      Whole sale resistor upgrade (the 25th anniversary mod replaces two original ones with glass resistors, I use Audio Note low noise resistors. This was also done before the 25th anniversary mod came out. Later after I learned about the 25th anniversary glass resistor mods I replaced the Audio Notes with glass ones but they did not work for me due to microphonic issues. I am back to Audio Note resistors which are also sonically better I felt. Maybe its because my overall system with the upgrades is really sensitive now or the microphonics with glass resistors could be system specific resonance. I have additionally replaced 30 to 35 others with Mills 10W low noise wire wound resistors (10).

The last one is the toughest to do. It was challenging to fit the 10 W Mills resistors in restricted spaces and there are many of them. They are about 5 times or more physically larger than the stock ones.

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 05/09/19 at 01:42:41

I have installed the adapted 6 gauge wire "fuse" in the fuse slot again and have been running it this way for the last 10 days and intend to continue it. Hoping Murphy's law does not come back to bite me as has in the past with other stuff. Having drunk from the poisoned chalice I am finding it difficult to go back.

Folks seriously do not try this one, depending on your level of OCD - mine is obviously high you too might not want to go back. I do not leave sight of the amp as a mitigating factor.

My modus operandi for now is when trying out new tubes is to have a fuse in and after a period of say 100 hours with those tubes go back to the wire "fuse" but always being in the vicinity of the amp when it is turned on. I am not so much worried of the amp getting destroyed, do not want to cause a electrical fire and burn the house down.

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 05/19/19 at 22:47:27

Yesterday I had one of those eureka moments and decided to try to wire the 4 pole Mundorf 4700 uF power capacitors in a hybrid 2 pole / 4 pole configuration thinking that this would get me the best of both worlds i.e. quicker responsive power supply while maintaining the deep filtering. More responsive delivery of instantaneous power peaks when demanded as power supply path way will be direct, not only exclusively going through the lengthy capacitor positive and negative plates, while at the same time much lower backgrounds because of the better usage of the plate surface areas in these large capacitors.

Having tried all three ways of connecting these 4 pole caps (2 pole, 4 pole and 2/4 hybrid pole connection) and also the earlier Red Mallory 2 pole caps I think the hybrid 2pole / 4 pole connection is the best by some margin. Kicking myself for not thinking of this before.

Music production is even more effortless for a system that was already effortless. There is an enhanced metallic sound of strings and cymbals …. more "floating in the air" effect also. Deep bass (my speakers go down to 24 Hz) is tighter and drum diaphragm reverberations palpable ….. that natural hollow drum “echo”.  Note: The ZMA does not go below 31 Hz (-3 dB) (Those Hammond output transformers roll off at 30 Hz) so I bi-amp the PSB T3 speakers with a Cary Audio SA 200.2 amp only driving the woofers down to 20 Hz and ZMA driving the rest. But even so this power supply change in the ZMA has affected bass beneficially also. Perhaps the same reason as how super tweeters though operating in the in-audible range, affect the audible spectrum. Tonality across the full range of audible spectrum is more vibrant, more natural and “in the room presence” even more real.

Title: Re: ZMA - comperhensive upgrade complete
Post by busterfree on 05/19/19 at 23:00:45

...The ZMA does not go below 31 Hz (-3 dB) (Those Hammond output transformers roll off at 30 Hz)...

Is this really true? Confirmed through independent testing?

I do not own an ZMA, but I am concerned that statements like these are an issue if not really true. I have seen similar statements about other tube amps in the 25-60 watt range on the internet. I don’t want to be all about measurement or specifications. More reason to stay with amps I already have. I do not care if they do not measure 20-20K Hz, but I hope they would.

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 05/19/19 at 23:40:55

I tested both the ZMA and the Cary Audio amp with Space-Tech Audio tester EAT-100. I do not have independent lab tests so I reported my readings. It would be great if there is an independent lab test floating around like you said but I am not sure if there is one. Alternately Steve listing it in the ZMA specifications would help. It is also evident by reversing the roles and connecting the ZMA to the woofers, quite the difference in bass output.

The Output transformers on the ZMA are Hammond Output transformer 1650 PA and the specifications given by the manufacturer is 30 Hz to 30 Hz. This aligns with my test on the EAT-100. Cary Audio also listed the specification for the SA-200.2 amplifier and the EAT-100 matches the 20 Hz they listed. BTW there are some Japanese transformers that I found that go below 20 Hz even 10 Hz but they are 3 times more expensive and shipping those heavy transformer from Japan is half the price of the transformers. Also do they not fit in the space on the ZMA.

I like bass so went through the expense of bi-amping to get it. That meant an additional amp, speaker wires, interconnects and speakers that go low down. I feel if the original recording has bass information, this needs to be reproduced otherwise that realistic feeling is lacking.

Title: Re: ZMA - comperhensive upgrade complete
Post by busterfree on 05/20/19 at 00:35:52

Cool. I see a response of 20-80 kHz for my amps on the product page, but I do not see something similar on the ZMA page.

Do you use a preamp?

I thought about bi-amping, but I haven’t gotten serious about it. I see a lot of folks using Class D amps on the bass.

Title: Re: ZMA - comperhensive upgrade complete
Post by bandrade on 05/20/19 at 01:37:03

I use CSP3 as a pre-amp enabling the bi-amp solution. I have the iFi Pro iDSD DAC which can output 5 V on the Single Ended RCAs and 10 V on the balanced XLR outputs so would have preferred not have the pre-amp but the loss of the full range of the audio spectrum (ZMA by itself) is one that does not appeal to me at all. In my opinion recordings that have these range of frequencies should be able to be reproduced as is for that realism and naturalness.

As you mentioned most folks tend to use a Class D amp to drive the woofers as the woofers require the most power of the 3 types of drivers and so class D being efficient would result in less power consumption and a smaller size. But the negatives makes it a non-starter for me. I feel Class D have to have too complex a circuitry that in turn influences the sound produced, instead of only doing its basic function of only amplifying the input signal without artifacts. I feel an amp should be as transparent as possible and Class D influence sound a bit. Also Class D amps cause RF noise in the other audio equipment around. In my opinion where there is no size and power restrictions as in a home audio system (compared to a car) and RF interference is an issue (as in a home audiophile system) a Class A/B amp is better. Might cost more to run but if audio performance is the only consideration, I feel a well designed class A/B amp is the way to go to drive those bass frequencies. Class A is the simplest in design but they are home heaters.

The tube/solid state bi-amping combination works well in my case (in lieu of a Tenor hybrid amp that costs $70,000/- or more). I had to work a bit on getting the phases to align. But once done and you know your system in and out it is excellent experience as more of the information on the recordings is output this way, instead of some being left out. Logically too expecting any one piece of equipment to do everything is probably unreasonable. I found that tube/solid state combo allows me to utilize the best of both properties.

I'll be the first to say this may not be the solution for everybody as it adds complexity: a larger audio rack and power supply/conditioning to cater to both is needed to start with. As well an additional amp, interconnects and wider frequency range speakers (which are typically 92 dB or less), speaker cables. These factors matter to most (and to me but alas my mind compels me to do it anyway).

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 06/03/19 at 01:06:55

Folks I took another step in this quest to further improve the ZMA.

I have now replaced the large Mundorf Mlytic 4700 uF HP+ 4 pole caps with 6800uF ones of the same make and type. As can be seen in the attached picture they tower over the transformers in the background.

There is a lot written elsewhere and on these forums as to why the power supply should be many times the actual power draw from the audio equipment it servers. e.g.electrical panel (dedicated circuit 20 A or 30 Amp circuit), wiring (10 or 8 gauge), high quality wall receptacles, high quality and capacity power conditioners etc. etc. Many of us have actually experienced the benefit of having a large power supply chain.

In keeping with this philosophy I wanted to increase the internal power supply within the ZMA for the longest time as this could be a choke point. Since Steve was limiting his upgrade to 3300 uF in the 25th anniversary mods I was hesitant, in spite of the feeling that that limit was more a business decision rather than a sonic one. I was hesitant also because I was wondering if the gains - if any - would be discernible enough given that my ZMA has improved so much already. I wondered if there was possibly no more room for improvement available. Time and time again it always got better with thought full upgrades so much so that I have now concluded that there is no such thing as a limit. Time and time again I thought the end was near and the next upgrade was going to be a waste but time and time again there were noticeable improvements as I mentioned in this thread. I now believe there is no hard ceiling, to use a cliché, the sky is the limit.

I believe the power supply within the ZMA does not have much excess available margin and that is why many on this forum have debated on limiting the bias current to 50, 60, 70, 80 mA or whatever and at what point the input transformers would be stressed and fail. I think the internal power supply is too close to the requirement of the amp circuitry, so suffers when the dynamics of music being played calls for instantaneous power boost.

Back to the point, this upgrade of installing higher capacity capacitors (3 times stock or 2 times 25th anniversary upgrade) made all aspects of music even more clear and precise. Extremely faint leading and trailing edges of every micro morsel of sound across all frequencies came into existance, bringing about a completeness and therefore realism.

I am impressed enough that I am now considering increasing the power capacitors capacity manifold !!! say 50,000 uF or may be even 100,000 uF or more, about like in very high end systems costing above $50,000 were the ranges are in the Farad range (not micro Farad range). I now have a lot of spare caps lying around – 2 each of the original red 2000 uF, the Mundorf 4700 uF and additional 10,000 uF that I bought sometime ago for another project which I shelved (DC offset eliminator) that I can utilize for starters. For space reasons, I am going to have to put it all on a separate “Power” box/base with additional higher capacity power transformers on it in as the ZMA transformers will most certainly not be able to handle the initial surge current as the capacitors charge. My preliminary thinking is leave the ZMA input transformers to only supply the various tube filaments and the new external high capacity transformers on the separate Power unit do the heavy lifting. The intention is also to include a CLC or better noise filter. Note currently the original ZMA has no standard filtering techniques being employed. Instead the ZMA utilizes large somewhat slowish electrolytic caps to “dampen” the noise rather than a full pronged attempt to “filter out” the noise so there is another reason to do this. Although the 47 uF F&T caps and the new 25th anniversary caps on the B – rail are an attempt to filter out some noise but is nothing like say a good old CLCRC filter combo.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 06/07/19 at 02:26:27

In order to gauge the effect of more power capacitance that I mentioned in my earlier post I thought I'll try re-installing the 4 pole 4700uF Mlytics (that I had removed last week) in parallel with the new 6800uF caps for a total of 11500uF per side !!!

After the install, I was a bit disappointing when I powered the ZMA and played music. This change seemed to have robbed some of the sharpness and clarity I had gained over time though this lengthy upgrade process. My immediate conscious reaction was to remove the added caps but I felt a niggling sense that it did not make sense. I hung on thinking there was some thing wrong perhaps a misconnection or a loose connection. 4-pole, 2-pole combo connection being more involved with both being 4-pole caps so I while I was redrawing the connections on paper I had a ah! moment I realized that perhaps it was because I started playing music soon after powering the ZMA. I wondered if the added capacitance resulted in the power transformers not being able to cope with simultaneously charging up the now larger combined capacitors while also powering the internal ZMA circuitry and driving the speakers (which is the greatest power draw of the three).

So I powered the ZMA half an hour before actually playing music so as to allow the capacitors to top up to their maximum charge. WOW! This did it. There is added subtle dimensions to the music, not dramatic as I did not expect huge gains at this advanced stage. Especially the lower midrange and upper bass frequencies seem to be a little more prominent so as to have inundated the higher frequencies a little bit.

I had way earlier upgraded the tweeters on my speakers at which time had to attenuated the higher frequencies by adding resistors (L-Pad configuration) in the speaker crossover network to balance the tweeters with the midrange and bass output. I am bi-amping with the Cary Audio amp exclusively driving the woofer but strangely this latest change of more capacitance in the ZMA has added to the bass output from the Cary Audio! I have now had to rebalance the tweeter outputs by reducing the aforementioned attenuation with a re-adjustment of the resistors in the crossovers. This was a pain as I had to adjust the resistors in the crossovers 4 times (working in the confines of the speaker enclosure) to fine tune the balance between the tweeter, midrange and woofers right again. Back on track again. Without a doubt the larger the power capacitors the better.

I am now able to play music at slightly lower levels (my speakers are 90 dB efficient) without loss of definition where as before I needed a slightly higher volume setting. I now have more choice in terms of volume depending on the mood and the situation. It might be because the higher the capacitance at the very source of (close to) the amp means proportionally lower the dependence on slower grid power for those high demand fractions.

Title: Re: ZMA - comprehensive upgrade complete
Post by BAndrade on 06/07/19 at 02:44:09

Picture of the additional capacitors in place.

Looking at it perhaps the title of this thread should be changed to ZMA - Extreme upgrade. ha!  At the outset of this adventure I did not think it would go this far!

This a temporary set up. I'll have to think of something to make it look more pleasant until I do a more dramatic 50,000 uF change which will require higher capacity power transformers and ancillary "Power Supply" box.

Title: Re: ZMA - comprehensive upgrade complete
Post by BAndrade on 06/09/19 at 01:04:04

11500uF (per side) put to the test.

The attached picture was 8s taken after the power was turned off as can be seen from the “OFF” position of the power switch in the picture. All tubes (2xOA3s, 4x7581As and 4x6922s) continued to be powered at full brightness for a few more seconds for a total of about 11 - 12 s.

8s to 12s may not seem like much but if one thinks about it, it is an eternity when the requirement is to supply fractional instantaneous boost power when the music being played calls for it e.g drum thump. These faster larger caps being downstream of the input transformer will be the primary source of power during increased demand periods with the slower electricity grid supply and much slower power transformers (transformers being inherently slow) then are only replenishing the charge within the capacitors i.e. the larger the capacitors the less the participation of grid power in directly supplying the ZMA circuit. This was my reasoning of going this extreme route of vastly increasing the capacitor size and I think is the reason increasing the power supply capacitors resulted in a fantastic positive palpable benefit even in an already highly improved system …. less grid noise is transferred within, in addition power is now being supplied more readily thus ensuring all bits of sound got even more real. There is enormous ease being felt as if every quanta (quanta may not be the right word being associated with light, but hopefully it conveys the message in the context of sound also) of sound is played more perfectly in time dimension and more over each quanta of sound is more true to the source - be it instrument or voices - being less influenced by superimposition of grid noise (even after power conditioning equipment) on pure music signals.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 06/11/19 at 01:26:02

Wondering if any of you folks have experienced this.

It seems to me that different periods - 15 minutes to 45 minutes - before starting to play music makes a difference in quality of sound output v/s background noise.

Playing music immediately after powering up was the worst scenario. It took about 2 hours to get that exquisite sound. So the shortest period to run the ZMA idle is about 15 minutes.

Looks to me that if the ZMA is left powered up but silent for about 15 to 20 minutes before beginning to play music caused the background noise level to be pitch black and music to be fabulous straight off the bat.

Interestingly if the ZMA was charged up for 45 minutes or more before starting to play music, the background appears to be ever so slightly less black than those experienced at the above shorter time. But now the speed increased to perfection and the music playback is better than fabulous – floating and realistic.

I have been deeply thinking why this is so. My thinking is that it is because there is no dedicated noise filter arrangement in the power supply of the ZMA but there is reliance on noise damping instead, in those large capacitors. So at the 15 -20 minute mark the massive caps are still not fully charged as yet and any ripple riding on the power supply after the rectifies get absorbed by the capacitors because there is slack in the capacitors to dampen the noise riding on the power supply. Where as at the 45 minute mark onwards the caps are fully charged and so some of the power line ripple simply bypass the fully charged caps and move on further down the circuit but now the fully charged capacitors far more readily supply current.

My preference is the fully charged state as it produces music that is just fantastically timed and detailed, the very minor increase in background level is not at all normally perceptible unless highly concentrating on it only with single mindedness, blocking all else.

I would imagine for stock ZMAs without massive amounts of capacitance the times would be proportionally less but in any case leaving the ZMA powered up for at least about 5 to 10 minutes before starting to actually play your music would yield the best results. Otherwise depending on how hard and what is being played it would take longer to reach that optimum point.

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 06/11/19 at 01:31:10

Are you saying that NOT playing music is required?  Or will it catch up eventually if music is played from the start?

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 06/11/19 at 03:45:01

I mean just turning the ZMA "ON" without actually driving the speakers. i.e. the source e.g. DAC etc is paused or off. Driving the speakers causes a draw  of power from the amp delaying the large capacitors from being fully charged.

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 06/11/19 at 15:53:13

Got it.  Thanks.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 06/16/19 at 12:20:43

Just for fun I decided to add the original 2000 uF Red capacitors for a total of 13500 uF per side. As a quic experiment I did the connections with alligator clips as shown in the picture.

Folks if you doubt music with such a drastic change from the humble beginnings of only 2000 uF per side has no effect, you are mistaken. You’ll think your ears have undergone a tune up – everything is even more crisp and clean.

Background is getting blacker more and more as there is now lesser and lesser dependence on the electrical grid for immediate power gratification. This background thing b.t.w. is not fathomable. Until it is moved further down you realize there is this lower level. Every time it is lowered the sound becomes more and more clear like more and more shine is being produced by constant buffing on chrome metal.

I probably reached the limit of these input transformers' start up current. I could hear the electrical flux building up in the transformers when I toggled the power switch to "ON". However running current through the input transformers seems to be lower based on the running temperature of the transformers being 10F lower than normal – 99 F vs 110F. However I have been only running like this for an hour now. I’ll take more readings further along and report here if the temperature drastically increases.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 06/23/19 at 18:58:41

Something huge in the works.

My drive to achieve more and more perfection or OCD in modern parlance has compelled me to place an order for input and output transformers made by the same manufacture as the original ones  on the ZMA but of substantially higher output.


My calculations and discussion with the manufacturer of the transformers viz. Hammond Manufacturing have led me to believe if driving higher wattage, lower efficiency wide frequency speakers the original transformers are close to their "core saturation" point at mid/high volumes levels. Definitely using KT88 tubes at higher outputs will exceed the manufactures specs for the transformers (even though the ZMA owners manual has listed KT88 as an alternate) entering the region of saturation of the transformer core. BTW the stock ZMA will easily drive speakers that are 90 dB or more efficient and that do not go lower than say 30 Hz or so. In this case these and all earlier posted upgrades will yield proportionally less results as the speaker demands on the amp are far less.

Thing is these new transformers are physically larger in size,I have no idea how I am going to fit them on the amplifier base. As with all the upgrades done so far if things do not work I have the option of going back.

While I am at it I decided to include a filtering section so also ordered a couple of 5H chokes and 47 uF Mundorf Tube caps. These definitely will have to be external to the ZMA base unit.

Both looking forward to it as well as not for the amount of work involved. Might be far more than I have done so far for any single upgrade task. To gain access to shoulder points I expect to remove a lot of the work already done and re-fixing it all back.

No rest for the wicked ...

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 06/29/19 at 02:33:11

Transformers, reactors and capacitors have arrived. No turning back now.

Not looking forward to the work involved which I figure will be far in excess of anything I have done on the ZMA so far. As they say "No pain, no gain"

The transformers are about 25% larger and heavier and will not fit on the ZMA base so will have to think of something which usually means much more work than usual on account of the trail and error this entails.

The picture shows the new transformers. I'll try to post another one showing the size difference side by side after I remove the old ones.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/04/19 at 02:48:46

The new input transformers are about 30% larger and weigh a ton. Original ones are rated at 150 VA and 173 mA while the corresponding figures for the new ones that I am installing are 243 VA, 288 mA.

The new output transformers are rated for 60 W v/s 40 W.

So size is a head spinner for this upgrade. See photo. The new one is to the left and the old removed input transformer is to the right. This was a case of getting the transformers of the power rating I wanted and thinking of how to fit them on the fly. There is very little excess real estate on the ZMA base to accommodate the new input transformers. The output transformers are only slightly larger, it looks like they are going to fit. Physical size must have been a consideration when Steve chose the transformers that he did. I feel especially the input transformer could have be higher rated, but 372 FX is the largest 600V transformer in the Hammond's line up that will fit on the ZMA base. The model I am installing is the 372 JX.

Can't wait to finish this project, only about 20 % done so far. If the original transformers are underpowered for my 99 dB, 300 W speakers than this upgrade will make a substantial difference on the other hand if they are not underpowered than the difference in sound quality will not be as much if any.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/11/19 at 02:40:18

Done, done and done.

Just powered up after completing the mods mentioned in the two posts just above. I am exhilarated both with the outcome and even more importantly because things largely went to plan. It actually works! And works it does. Only blew the fuse once during the test phase on the work bench (kitchen table) because I missed insulating a wire with shrink tubing. Considering that that was the only mistake after working on about 60 to 70 close quarter and sometimes inaccessible soldering points I am happy with myself. I had to celebrate the occasion by myself alone with a single malt and the evening off just listening to my now much elevated music. By myself because as while the wife saw me toiling away for days on end she did not seem to appreciate the work done or how things could have gone wrong. Importantly we are both happy to have music back and back with a bang.

I will come back with details and pictures. Could not wait to post the good news.

Title: Re: ZMA - comperhensive upgrade complete
Post by Jeff of Arabica on 07/11/19 at 05:17:58

Bonny, impressed in an understatement!  You are my DIY hero brother!  

I have been following your journey the whole time.  Far have you come since our original collaboration on some of our early ZMA modifications.  You have taken the ball and ran 1000 yards beyond the point I reached with my modifications.  I am envious of the transformer upgrade as that was an area I researched tremendously but the fell short as the transformers I wanted to install would not fit on the plate.  Plus, that was a soldering venture I had not the time  or patience to commit.  

Your post hit home as there were many times during my upgrade process where I was up to my ass and elbows in work on my dining room table convincing my wife that it was all worth it.  While she may not truly grasp the ROI on the improvements, the time, money, and effort were ABSOLUTELY worth it.  My ZMA is Divine.  But.........   there is no doubt in my mind that it can't hold a candle to yours.  

That said, congratulations my friend and a fine single malt is such an appropriate way to reward yourself for enduring.  Bravo!  I might need to invite myself to your house when I am in your neck of the woods to have a listen.  Based on what I know and what you have done, it would be well worth the effort.  


Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/11/19 at 22:00:20

Jeff, you are welcome buddy. If ever you are in the Toronto area be sure to give me a buzz. It will be my pleasure to have you listen to my system. This invitation is also to any one on the forum including the guru Steve.

In a sense you and Vyokyong were the brave ones that got me taking the first steps. I was initially hesitant to void the warranty. Then you made a statement somewhere on this forum that for you audio quality in the present trumps all else (e.g. longevity, warranty etc. etc) which struck a cord in me, being of the same mindset in the first place. No point in living with less quality of a longer duration even if say component life is shorter or the warranty is voided if it is within your means to improve things. Also these point to point wired amps are built like a tank and quite easily repaired unlike solid state amps.

Cheers to you as well. Have one on my behalf while enjoying your system.


Title: Re: ZMA - comperhensive upgrade complete
Post by Steve Deckert on 07/13/19 at 00:21:50

Mostly we should all congratulate you for still being alive with all the microfarads.  Also congratulations you've just built yourself a pair of TORII Monos : )

I'm tipping a beer to you right now.


Title: Re: ZMA - comperhensive upgrade complete
Post by Jeff of Arabica on 07/13/19 at 03:24:43

What amazes me....   this 40 watt ZMA is powering my Essence Audio Amethyst 10A Reference speakers beautifully.  Volume is more than sufficient, about 85% output and no clipping for a listening level beyond conversational.  Soundstage is wide...  reaching 180 degrees with ease.  Bass is beautiful and holds it own amidst the midrange and treble prowess of this speaker stack.  

These speakers weigh in at 90dB efficiency, 10 separate drivers from the 12" bass drivers to super tweeters, the ZMA ain't intimidated and taking no $h!% from this formidable speaker system.  

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/13/19 at 05:09:05

I feel honored Steve.

You brought up a good safety point. I should have mentioned about the dangers of working with such high power reserves, just to put it out there. Normally I do as when I mentioned of the dangers when experimenting 8 gauge wire in place of the fuse, because I breath and live safety as I work for a reputed electric power generation company that supplies power at 500,000 V to the Ontario and by extension to the North East American electric grid. Looking back I got caught up with the single minded purpose of improving SQ so missed mentioning the safety aspects.

After the upgrade work and testing is done and once assembled with all raw contacts inside or insulated if exposed outside as in my case it should be safe for operation.

The effects of so much capacitance though is just giddy and needs to be experienced.

I must also humbly confess I learned a lot from you – directly from your white papers and posts but for the detail technical aspects indirectly by passively studying your amps at great length. While I have experience in electrical equipment and parts such as capacitors, resistors, diodes, rectifiers, solenoids, motors, generators etc. in many other different applications, I did not until a few years ago have much experience in audio circuitry and have used your amps to self study your designs. There are times I believe I read your mind through your designs and figured out why you chose a particular path or component quality or size.

This is the only forum I am active on as I find it to be an environment that checks all the right boxes for an open discussion designed to elevate each others audio experience and is the reason I decided to spend bit of my time chronicling my experiences to give back to you and others in this audio community.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/13/19 at 05:35:38

Wow, Jeff those speakers take the cake.

Do they have active crossovers? If so that could be the reason the ZMA is able to drive them sufficiently.

If not, I am dumb founded.

In either case it might be interesting to experiment with bi-amping them. Good as things are now, I feel you could possibly scale dizzying heights. Even though they sound good as is with the ZMA alone, it's possible that the drivers will respond even better with more power that bi-amping would entail. I won’t be surprised if the timing and leading and trailing edges extend even more than now.



Title: Re: ZMA - comperhensive upgrade complete
Post by Jeff of Arabica on 07/13/19 at 05:57:16

Hi Bonny,
No active crossovers.  The drivers are 90dB so in the transmission line cabinets they are probably closer to 92dB.  Anyway, they are nott what I would consider high efficiency drivers and there are 10 of them!

The ZMA is handling them like a champ!  I am a proud father  :)

But, my ZMA got drafted after my Canary Audio monblocks went in for a major overhaul/upgrade.  My ZMA's are assigned to my Hegeman Model 1A's, but called to duty these past couple months as I wait for the Canary "Reference Two" mondoblocks to come back.  They are 300B based 80W monoblocks that are being upgraded to the new flagship, "Grand Reference" model.  

I definitely think that bi-amping could be a good option.  I am hesitant to bi-amp with different amps and these Grand References are cost prohibitive to obtain a second pair.  They retail for $42K.  

A ZMA tri-amp setup would be something I could get excited about!  

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/13/19 at 13:54:53

Jeff you stole my thunder. Just kidding I am happy for you. I just checked the specifications of Canary Audio Grand Reference two monoblocs: 16 of 300B tubes in parallel push pull arrangement! These itself will cost more than a very good tube amp and +/- 1 dB from 8 Hz to 80,000 Hz really! You really need those super tweeters and the 12 inch woofers to utilize the wide audio spectrum these amps are capable of. You are on another planet buddy.

BTW Parts Connexion has an almost new PS Audio P20 on sale. Just saying it would do a system like yours a world of good instead of the P10. I have bought a lot of parts from them and am in touch with the owner Chris and could try to get you an even better price for you.

Given this new revelation from you I think you will be disappointed with my set up. It is I who will benefit from having a listen to your system.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/13/19 at 23:11:14

Time for some pictures of the development process.

This one shows the mod done on the right side with the old set up on the left all powered up and playing music. I decided to test it at this midway stage to enable me to discern the difference between the new and the old setup by listening to the difference on the right v/s the left channel.

Conclusion: the right channel was significantly less labored with the mid-range and woofers benefiting tremendously. More audio information on the right channel compared to the left.

It might be hard to tell from the pictures but the right set of tubes were more brightly lit than the left ones.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/13/19 at 23:17:42

This one shows the temperature measured on the right channel new input transformer exterior surface. Quite a bit lower than the that of the old left channel 38C v/s 51C. The next post shows the temperature on the left channel old transformer.

My solution to install the new larger input transformer was to install it on 5 inch stand off's. This allowed for over hang above the speaker binding post. The larger new transformers would not fit in the smaller space.

Turned out there were additional benefits to being placed up and away. The left updated channel was eerily quite when music was not being played as compared to the old unmodified left channel. Could be because of the inevitable leakage flux out of the transformer core was now not affecting the speaker binding posts. In the old arrangement the speaker binding post were less than half an inch away from the transformer. Also now the new input transformer being up and away there is no (or less) coupling of the leakage fluxes of the input and output transformers allowing each to function more independently without interference on each other. Steve oriented the input and output transformers at 90 degrees to each other so as to minimize the interference of the two fluxes. In the new arrangement it went a step beyond they are not only at right angles to each other but also physically apart. Because flux density decreases significantly with distance it is more effective in reducing the influence.

The down side of having the input transformer - which is the heaviest of the lot - higher is that it raises the center of gravity of the amp as a whole making transporting it by carrying it more tricky. It was by chance that this is my last mod so I do not now have to move it much if at all.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/13/19 at 23:19:25

Picture of the temperature of the left old input transformer.

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 07/14/19 at 00:05:52

If the tubes are brighter, are they being pushed harder?  (at the same bias I assume)

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/14/19 at 01:00:41

Good question.

It is the filament voltage that will affect the brightness of the tubes. So bias can be anything: low or high the brightness should not be affected unless biased way I mean way out of the allowable range which no one is going to do. Even than I think the brightness change will not be such as to be discernible (I think, I have not tried it nor do I want to).

So since we are talking of filament voltage and current a good way to look at it would be a normal old fashioned filament bulb in a house hold circuit. A 100 W bulb will consume 100W if given its designed voltage which in north America is 120V is maintained. Given that the voltage is fixed the current consumed by the bulb will be defined by the resistance of the filament in the bulb - which is also fixed. Now suppose one was to load that same circuit in the house on which this bulb is by adding other loads say a turning on an electric heater and other stuff the bulb will continue to be lit with the same brightness only if the supply can keep up with this extra load. If the supply is weak the bulb will dim as there is a drop in circuit voltage.

Similarly in an amp if the input transformer power rating is lowish such that its core is overfluxed or close to being overfluxed it will not keep up with the load demands of the various loads within the amp that rely on the input transformer and the brightness of the filaments - which is one of the loads - will be lowered and the behavior of the other things in that circuit will be affected. If say the original transformer was of substantially higher VI rating by my installing an even higher rated transformer will not increase the tube brightness as the load which is the tube will not consumer any more power than it's design. That would be a waste of money and time.

So what I am trying to say in this long winded explanation is that one can only suppress a load's (e.g tube) output and that it will not consume more power than its rated design. So by increasing the input transformers rating I have ensured that the filaments are being supplied by adequate enough power to operate the circuit components upto and no higher than design rating i.e. there is no suppression of that components output due to a paucity of power supply.

So yes the tubes are pushed harder but up to their rated design level. I am sure you are aware that it is the filaments that supply the electrons (indirectly by heating the cathode) that flow to the plate and the tube grids than control the flow to the plate to modulate the sound to match that of the music. So a copious supply of electrons will ensure that ease of producing music. Lack of supply electrons will take away portions of the music.

I hope the message is not lost in this long explanation: in short yes the tubes are driven harder but to their design rating which I like. Why have a race car and use it as a street car (if allowed) just to ensure longitivity.

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 07/14/19 at 01:14:34

If I supply more than the spec'd 120V to a 100W light bulb it will burn brighter (and have a shorter life) than at the spec'd 120V supply.

I take it that you haven't increased the voltage the tubes see?  I have nowhere near the understanding of how this all works that you do, I'm just curious about the increased brightness.  Are saying that the stock configuration doesn't fully utilize the design potential of the tubes.  I do remember reading for several different Decware amps that Steve intentionally doesn't push certain tubes very hard.

I've never noticed a fluctuation in my ZMA tube brightness while idling or playing.  I don't know how this relates, if at all.

Your modifications have made me even more curious to hear Steve's big monos.  They were never a consideration due to cost but my upgraded ZMA is already well past the halfway mark -- if I'd only known then what I know now!

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/14/19 at 02:42:26

To continue the analogy I am not upping the voltage to above 120V to cause the 100W bulb to burn brighter. I am bringing it to 120V i.e. bringing the filament voltage to the rated 6.3V under load conditions where as it appears the old transformers were loaded so much as to suppress the voltage hence dimmer tubes. In my case they are brighter because it is brought up to spec.

Yes it does appear Steve likes to design his stuff with longitivity in mind. Hence for the pre-amps such as the CSP3 he has deliberately staved the filament voltage supply ensuring longer than design life for the tubes and the components in the amp. In the case of the ZMA though I suspect it is because of space constraints. The physical size of the higher rated transformer caused the move to the current one. Only Steve will know the exact reason. In any case it fits his preference towards longitivity.

For him it is a balancing act getting the best bang for the buck in terms of longitivy only versus performance only criteria. As for me I am not constrained by the requirements imposed by others e.g. long life as I am doing it for myself and my personal bias is whole heartedly towards performance.

Mind you I do not over load anything beyond design but to design. So the life of my upgrades will still yield 20 years of operation. If I could get further performance improvement and it meant a life span of the equipment of 10 years I would still be happy. But going beyond design rating usually bring other undesirable artifacts into play so I like to stick to design knowing fully that the design specifications for industrial equipment (may not apply to audio equipment as it seems to be a free for all approach i.e. no national or international standards) is still conservative.

It does not appeal to me that I am using my equipment sub-optimally for 30 years when I can use it optimally for 20 years.

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 07/14/19 at 17:26:26

That makes sense.  Due to my limited knowledge ... do I not see a change in my tube glow between idle and full bore since these amps draw full power even at idle?  Am I confusing wall current with something else?  Since the transformers seem to stay the same temperature either way, I may have answered my own question.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/14/19 at 18:41:19

My statement in my earlier post needs elaboration as it is not so cut and dry. I said "It does not appeal to me that I am using my equipment sub-optimally for 30 years when I can use it optimally for 20 years"

I would not fret too much either way as I think Steve has found the right balance for him to give the lifetime warranty while maintaining very good performance.

Unfortunately in life one can't have everything, there are compromises: in this case a conservative design approach for long life warranty or a absolute performance driven approach not caring if it involves more maintenance along the way.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/14/19 at 18:52:14

The tube glow should not change from 0W output to 40W (full load) of reasons I mentioned earlier, but the transformer temperatures should increase from no load to full load (40W). It will take some time for the temperature to manifest and stabilize to the full load level on the exterior of the input transformer as there is a lot of thermal inertia within the iron and copper masses of the transformers. After all the 40W plus losses (hysteresis and eddy currents losses increase in the transformer laminated core as current in the transformer coil increases) in the laminated iron core at full load are ultimately coming from the source.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/14/19 at 19:39:58

My high tech test bench.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/14/19 at 19:45:42

A close up picture of ZMA inverted and loaded on the test bench (kitchen table) to enable taking measurements. I used my home theater speakers - portions of which can be seen - to present a load to the ZMA as they were easier to carry to the "test bench".

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 07/14/19 at 19:46:32

At what point will you just bite the bullet and get a bigger plate?

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/14/19 at 20:05:17

No more upgrades. Done, done and done. Time to sit back and enjoy. Also every body at home is literally tired of seeing my face buried in the insides of this amp.

Aside from the obvious performance gains. This was a fun learning exercise, always pushing the limits just enough to stay out of trouble.  got to put my non-audio technical experience to use. Most of the knowledge is transportable from one field to the other and so I am richer in the other fields as well due to this project. Audio is unique as there are no national codes or standards so I have learnt a lot from first hand experience as to what works and what does not. I find there is more "hoopla" in the audio field than any other field. I'll share the lessons learnt in the coming days as I am sure there is take aways for everybody.

Title: Re: ZMA - comperhensive upgrade complete
Post by Jeff of Arabica on 07/14/19 at 21:01:07

Bonny, your pictures bring back memories...  My journey was pretty fun and very educational too, but I would be lying if I said there were no moments where expletives were blurted and tools thrown.  It was intense at times but once done, all that much more satisfying.  You made me laugh with your comments about the family and having your face implanted in the underside of the amplifier.  That, I can relate to.  

This ZMA is a great amp stock.  With the upgrades we have done (especially yours) it is a greater amp.  And despite having my crazy Canary monoblocks, I still love the sound of this amp!  While a very different experience with the ZMA in comparison, there are things I like about each and enjoy listening to them both with the different speakers I have in my stable.  

Do you have a pic you can send of the finished amp?  

Title: Re: ZMA - comperhensive upgrade complete
Post by JD on 07/14/19 at 22:14:13

Congrats on being successful. Time to enjoy all of that hard work, well done.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/14/19 at 22:38:52

This picture is a good example for why my folks were tired of it all, cannot blame them. The whole kitchen table and surrounding area was taken over.

Note: I would evacuate everything after every 2 to 3 hour work phase for the day. Not an easy task with those now unbalanced heavy transformers.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/14/19 at 22:50:52

This is the photo of it all boxed back and up and running.

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 07/14/19 at 23:03:10

I think I can see a bulge in the case!   ;D

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/14/19 at 23:13:13

And this one is of the extensive power filter network comprising of 6 different values of capacitors, the smaller of which are located inside the amp and the two larger ones are on the outside seen here nicely hidden behind the amp not seen from the front along with the massive 5H chocks. Total power capacitance is 13500 uF per side for total of 27000 uF for the amp. After power off the amp stays on for a full 19 seconds now!

Note: as Steve said there a lot of reserve power in those capacitors even after power off. Here they are locate at the back inaccessible to anyone so I have not insulated the leads.

My system is so quiet now you can touch -I mean touch- your ear to the drivers and they are dead silent when no music is being played.

This level of quietness really makes a difference for the ability to hear very fine detail. If there is a buzz/hiss, even a slight one from say an inch from the drivers, when no music is playing and you cannot hear the buzz when music is being played it means that the buzz frequencies are either accentuating, nullifying or mitigating certain actual music frequencies - depending on the where the troughs or peaks of the buzz/hiss frequencies are w.r.t that of music frequencies thus causing the music to deviate however small from the original recording and the actual buzz to be not heard.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/14/19 at 23:23:42

Jeff, did you mean the above finished pictures or a close up of the internals after finishing it all?

Also did you also mean send to you by PM or post here?

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/14/19 at 23:37:08

Thanks JD.

Title: Re: ZMA - comperhensive upgrade complete
Post by HockessinKid on 07/14/19 at 23:46:43

Very cool modifications to the ZMA Bonny. Way to take it to the max, then beyond.

What's next? Maybe a new exotic wood base?


Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/15/19 at 00:20:17

Thanks HK.

There is nothing else on the cards.

How did your 25th anniversary mods go? I remember you asking about WBT silver binding post and RCAs and the Furutech IEC connector. How did it work out?

Note if you did not hear additional finer details it could be because other things in the entire audio chain from source to speakers including the internals in each of the equipment (say fuses etc.) are limiting those mods. One's system is defined by the weakest point in the whole chain. It is the weakest (limiting) factor in the audio chain that you ultimately hear no matter how high grade all your other components are. Unfortunately that is the way it is. This is an expensive hobby.

Title: Re: ZMA - comperhensive upgrade complete
Post by HockessinKid on 07/15/19 at 00:46:29


My ZMA with limited mods done by Steve sound great. Thanks to your suggestions, Parts Connexion's WBT sale, and the 25th Anniversary mods the amp has been taken to a another level.

The only weak link I had was an aging stylus on my Dynavector 20x2 low output cartridge. Now that it's been retipped it's game on. My Ray Brown Soular Energy album pressing (Pure Audiophile label) absolutely blew my mind this morning. Everything, including CD's and TIDAL streaming just sounds amazing. Enjoy.


Title: Re: ZMA - comperhensive upgrade complete
Post by Jeff of Arabica on 07/15/19 at 00:48:38

Perfect Bonny!  That’s what I was looking for.

Your table looked like mine. My wife walked in one day and literally said, “Mother of God!!”

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/26/19 at 02:20:48

Folks, thoroughly enjoying the upgraded ZMA these past days, nicely burnt in by now.

The KT88s I have are back in business, putting on quite a show given the added power provided by the mods in the ZMA. Prior to the transformer mods the 7851As were the tubes that I settled on, now they seem puny.

Anyways here is a recap of the things I learnt from doing this project that I thought will benefit all. I'll post them one at time to reduce both the amount I'll have to type and you read in one go:

Learning 1:

Go the whole hog i.e. think about the whole audio chain – from source to speakers when accessing for weakness in your audio system. Minor improvements here or there may not result in the improvement you expect for those minor mods. Bottle necks in the rest of your system may choke this latest minor upgrade you did not allowing it to bloom.

The weakest of the bottle necks in your entire audio system will define the SQ not your most recent upgrade even if you have spent a lot on it. As I said previously the weakest chain link in a ships anchor chain will define the tensile force at which the chain breaks not the strongest link (say your latest upgrade) in that same chain. The strongest chain link if tested on its own may yield or even break at a much higher tensile load but put together in the chain along with that weak link, it is the weakest link that calls the shots causing the chain to break at a lower load and the ship to drift and get wrecked. Similarly for audio. This fact may lead you to be disappointed with the latest bit of upgrade you have done even thinking it did not work. In short if the upgrade is rooted in science and not in voodoo (e.g. silver v/s copper as a electrical conductor) it will work, it has to work, only that other things in your audio chain may be blocking it from expressing itself.

It's a judgement call as to what your weakest link(s) is/are and then eliminating those with good science not just conjecture and emotion. Hopefully some of the info in this thread helps in making your decisions.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/28/19 at 02:55:29

Learning 2:

Increase power supply capacity many fold beyond that required by the audio circuit at both the macro and micro level. Macro level: main power supply/ main conditioner and Micro level: within the pre-amp, amp (transformers, capacitors). This fact may be counter intuitive, being more used to everyday electrical appliances (e.g. toaster, oven etc.). In these cases it would be a waste of resources to increase power supply beyond that is required by the appliances. The load (that toaster, oven etc.) will only draw the power it requires no matter how large the supply capability i.e a 1000W toaster will only consume 1000W whether you have a 2000W portable generator or a 10,000W generator at the camp site. Where as when it comes to audio it is completely different: power requirements vary wildly micro moment to micro moment unlike a oven because the audio input signal frequency changes wildely with a resulting corresponding impedance fluctuation. Delivering power under these conditions needs a paradigm shift in thinking from that of day to day equipment. The power supply reserve has to be large and than some to supply those momentary peaks without strain, also it has to be supplied as soon as it is called for. Otherwise dynamics and timing the two absolutely key ingredients in music will be affected.

Hence these things matter: wire gauge, length (as small as possible) and quality, wall plug, IEC quality and grip tightness, fuse quality, size of power capacitors and quality of power capacitors (low ESL/ESR capacitors), large wattage resistors, high amperage ultra-fast diodes are some of the internals that contribute to delivering power to the circuitry no sooner it is needed. I came up with a simple test to gauge if my connectors (wall socket/plugs, IEC connectors) are grabbing the prongs tightly and are of high quality and the contact surfaces clean making for a good electrical connection: with the amp or any device running at full load for at least an hour take the temperature with an infrared thermometer of the connection at the plug/wall socket interface and compare it to the temperature of the supply wire about a foot or more away from the plug. The tighter and better the connection the lesser the difference if any. It’s a crude test but it does work especially for higher amperage equipment. This test saved the day for me for my main power conditioner IEC connector. I upgraded the male/female IEC connectors and the wall socket/plug and the temperature difference got close to zero from 2 to 3 degrees before the change.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 07/31/19 at 00:57:21

The ease with which the ZMA is now driving KT88s got me to think of trying KT120 tubes. Upon checking the specifications of the KT120s I found that the input transformers I just installed (which are if I am not mistaken even more powerful the Torii Mono’s transformers) will be able to handle even KT150s however the new output transformers I put are the same as the Torrii Mono’s (except the Mono’s have the potted version) will saturate with KT150 tubes so the highest tube I can safely install in the modded ZMA are KT120s.

Just placed an order for a quad of Machlett KT120. Cannot wait to give them a swirl. On a side note : on doing some research it seems that Machlett tubes are better than Tung-Sol and more over as a company Machlett have better pedigree than Tung-Sol. Below is a direct quote from Machlett website regarding comparing their KT120 tubes with those of Tung-Sol.

“These (the KT120s) are our own design and not to be confused with the lower end Tung-Sol tubes which share too many similarities to a KT88”

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/02/19 at 23:14:31

Learning 3:

Bybee products do not work for me. Bybee products (and they are expensive) are some of the few things that I purchased based on curiosity rather than science and electrical principles. I fell for the hype of “quantum” theory on which they supposedly work. These theories were subjectively verified by reviewers and advocated by some ardent Bybee fans but no laboratory based scientific measurements are available anywhere.

If there are any hugh Bybee fans out here I apologize, I have personally concluded after more than 2 years of observations that they do not work. I think the fans might be confusing a slight change in sound (sometimes imagined) even for the worse as improvement because improvement is what they paid for and the brain is making them believe it is (placebo effect) and companies like Bybee are I think exploiting this fact of human nature with esoteric claims. This placebo effect was happening to me initially and so I bought a few of the products but there was always an unease as to their efficacy. Now after more than 2 years and the initial euphoria gone and many A/B tests (some blind tests with my friends) as objectively as is humanly possible I have concluded that their products generally do not work. The best I can say is that some products may not deteriorate the SQ so I would label them as dummy innocuous expensive products.

Also possibly some folks on forums may be hesitant to admit that they made a mistake. If that's the case it will make other folks fall for it as well.

I would recommend you save your money and spend it on other more effective things.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/05/19 at 01:24:16

I have now been using KT120 output tubes for 5 days.

After I installed the KT120s and no sooner I started playing music it bought an unconscious smile on my face even before I set about consciously trying to figure out the impact as one would when trying out anything new.

Because these tubes have a higher output, it is obvious that the bass and to a lesser extent the midrange drivers have benefited further in spite of all previous improvements. And all along I thought I had no more margin for improvement.

Particularly beneficial in my situation I think. As mentioned previously on this forum thread I have PSB T3 speakers, they each have 5 drivers, 3 of which are 7.5 inch in size. These 3 drivers separately operate from the lower midrange to 24Hz handing over from one to the next as the frequency lowers from 750Hz to 24Hz.  The T3s have quite a flat +/- 3 db window all the way from 24Hz to 24kHz and are 89 db efficient anechoic or 91 db real world. So installing the KT120s have improved the overall balance between high, mid and low range frequencies for me. Even though I thought it did I can see now with the installation of the KT120s that previously the KT66s and KT88s did not have the whomp to easily drive these 3 drivers with the felicity as is now.

When I was younger and inexperienced I used to vacillate between a preference for accentuating treble and at other times bass or both as the sizzle of the treble and the impact of bass were both enticing depending on which phase I went through. With maturity I have come to realise that what elevates music to the epitome is a very flat response across the widest possible range frequency wise: ideally from 1Hz to infinity but in reality to the extent possible from 18 Hz to say 100,000 Hz. Sounds outlandish but let me explain my thinking. The flatter and wider the range on both sides of 20 Hz to 20 KHz the more exquisite the music will be even if ones conscious hearing ability is nowhere near that range’s extremes. I think we hear or rather experience music with the ears and also other senses particularly the skin, no kidding. Here is why. I was in contact with the design engineer of TakeT the highend supertweeter manufacturer from Japan, he conducted blind A/B tests placing very mini supertweeters (very light and about 1 inch in size – I have 4 of them myself) on subjects cheeks while listening with headphones and he says that the candidates experienced elevated music experience with the real supertweeters v/s dummy ones that looked exactly the same. In our communications he came across as a true no nonsense audio research scientist. He says that TakeT Batmaster supertweeters (which b.t.w. I have) goes beyond 150,000Hz he does not know how much higher as the Japanese national laboratory (or it could have been a University lab - I forget which) instrumentations where he tested them had a limitation of 150,000Hz and his readings were offscale those instruments.

On this subject of frequency range I also think we will never ever be able to exactly produce natural real sound (but only try to approach it) because we are still talking of reproducing within +/- 3 dB of 20 Hz to 20 KHz and we are extremely pleased if we achieve this. But natural sound is 0.000000001 Hz to infinity within a tolerance of +/- 0 Hz impossible to achieve. That is why no matter how good ones system is if the exact same song is played by a live band at exactly where the plain of speakers are one will easily tell a live band even from a really expensive system. I realize I am kidding myself when I say my system sounds live. The more appropriate language would be "live like".

I have come to believe that the very low frequencies and the very high frequencies though not audible, influence the air in the room just like live music would which in turn influences the audible frequencies. The air pressure peaks and rarifications of all frequencies (humanly audible and beyond audible) act cumulatively to produce a different resultant of air patterns that reaches the ear.  What we hear is the summation of the whole range of air pressures and rarifications just like in live music. Any instrument be it a drum, a guitar etc. produces not only the frequencies we hear but also the extreme frequencies we do not hear. The question to ask is why would sound emanating from any device emit only the frequencies we hear. With age we hear less but that drum or guitar still produces the frequencies beyond our now limited hearing that it produced in our earlier years. Because of this influence super tweeters work to enhance the music similarly. Similarly as your speakers go below 20 Hz.

Based on these concepts when choosing speakers to buy, I look for the most efficient speakers that can deliver the most frequency range – off course budget limitations has to be factored in. In my opinion if speakers roll off at below 50 Hz or even 40Hz a lot of music information from the music recording is lost straight away even though the midrange will be beyond superlative. The missing bass in this case feels unnatural and likewise the super high frequencies.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/05/19 at 02:36:29

Picture of Machlett KT120 tubes performing in all their glory in the ZMA.

Great to be FOAK for the ZMA.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/06/19 at 23:05:48

Learning 4:

Reduce noise in the power supply as much as possible - to the nth degree. I myself have gone exceedingly overboard w.r.t cleaning the power supply. I use a Furman IT Reference 20i power conditioner combined with a Blue Circle BC 6000 conditioner both rated at 20A and a Akiko Corelli conditioner. While each of these would on its own be enough they each take care of different aspects of power line noise so work well together all noise from the lowest to the highest of frequencies. Additionally I have numerous mini noise suppressors by iFi power at each devices IEC connector, a iFi USB galvanic isolator and iFi Gemini USB 3.0 split cable that carries the signal and USB power separately at the Roon server, a Furutech Flow 28 at the DAC etc. and even some Bybee Quantum purifiers (of all the things I have done I think the Bybee’s are more on the hocus pocus side – I am not sure they work as claimed but at any rate they do not degenerate the sound). Also I use a dedicated 10 gauge power line directly from the breaker panel (not running closely parallel to power lines of other circuits) for audio with a Furutech NEC wall receptacle. In all I estimate I have spent about $12 to $13 grand only on power conditioning – I said nth degree after all.

The goal was to simulate 2 a.m. night like electrical grid conditions during the day. I selected the Furman/Blue Circle/Corelli combo instead of the PS Audio P10 as I thought it was not sufficient capacity wise (see learning 2) and it’s sibling the massive P20 was not available at that time. Besides, I am not a fan of regenerators per say. They produce a “pure” sine wave electronically by first chopping the AC and then reassembling to form the sine wave in minute steps which will never be the same as a true analogue sine wave produced by mechanical generators in a power plant just like a very expensive DAC will only approach the analogue nature of a turntable but never get there. Though the P10/P20 have multiple other benefits like voltage regulation the jagged re-assembly of the wave over-rides it for me. That is why I think PS Audio P10 specs talks about noise reduction by greater than 80 dB only above 100 kHz.

Additionally where possible eliminating power supply noise internally within equipment yields even better results as the noise is removed closest to the actual delivery point (input and output vacuum tubes) as was my experience with the modifications to include power supply filtration in the ZMA.

I found that having as clean a power supply as possible enables hearing of extreme subtleties in music and the overall tone improves such that the sound is more authentic meanings string instruments sound more like actual strings not simulated (electronic) strings: stings vibrations can not only be heard but also felt and imagined approaching that of real life. Like vise for percussion, wind instruments and voices. Music sounds natural, real and live. Noise reduction makes a profound difference to SQ. Reading Steve eloquently elaborated 2 a.m. music listening experiences which got me to think “why not try to get that experience during the day?”.

Also as I mentioned somewhere earlier but is worth repeating here: noise distorts music as the peaks and troughs of the noise frequencies when present concurrently with music frequencies produces a resultant outcome of accentuating or diminishing actual pure music just like noise cancelling headphones deliberately superimpose an opposing frequency to suppress noise thus cancelling each other out. For noise in the power line case the noise because it is random in amplitude and timing i.e not exactly superimposed w.r.t. music may result in partially opposing or partially accentuating music frequencies so it either partially cancels or accentuates certain music frequencies causing it to deviate from actual.

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 08/07/19 at 01:01:22

Do you have regular fuses back in or are you still using the copper wire?

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/07/19 at 01:26:55

Still using the 8 gauge ultra pure copper wire in place of the fuse. Though I very much like the peace of mind of a SR Blue fuse (the next best thing according to the crude tests I did) the difference with the copper wire is addictive. I am trapped with this unwise decision. I am not as much concerned about equipment damage. What concerns me most is it being a fire hazard. I take my precautions as with always being around. Always being around will not prevent equipment damage as it happens fast - if a fault develops- that only a poised safety device like a fuse can prevent but I can easily prevent a fire.

Needless to say while testing e.g. after every upgrade I first start with a fuse in and after ensuring stable performance for a few hours usually the next day or two I switch back to the 8 gauge wire. Same when I switched to the KT120s for the first time just in case the they developed a internal short in transportation.

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 08/07/19 at 01:42:06

I don't see any fire extinguishers in your pictures.   ;)

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/07/19 at 01:53:33

I don't think I need a fire extinguisher poised and ready as the probability of a short and a fire is very low after the initial test phase.

Only if I leave the area and the initiating small spark propagates (there is very little highly combustible material internally in the ZMA) then there could be a fire hazard. Since I am around at the smallest sign of trouble I just need to turn it off.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/07/19 at 23:07:44

Expanding on the safety issues with a wire in place of a fuse. The reason I am kind of comfortable doing it is the probability of a fire is very low. In decades I have never seen a stable equipment suddenly catch fire. It is more likey that any piece of equipment will open circuit (a resistor or capacitor or diode aging ) and die rather than spontaneously catch fire.

The reason manufactures put a fuse is out of abundant caution, Murphy's law being what it is. And that is why I also don't leave it unattended for long periods. Besides being a tube equipment a little more caution is a good idea.

Also manufactures install fuses incase customers make mistakes like dropping coffee or metal pins into the equipment when running or overloading it etc.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/08/19 at 22:57:09

Learning 5:

Having done many changes over a short period of time, I have refined a a method for judging effectiveness of an upgrade.

When trying to ascertain whether an upgrade was effective one has to make a concerted effort to remember that change by itself in not an indication of greater accuracy and to try to objectively judge if it is just change that one is perceiving. Very often because we psychologically want improvement to show up being humans it is possible to perceive change as improvement and pat ourselves on the back thinking that money and time was well spent. In a way I am thankful to Bybee "quantum" products for teaching me this until it finally dawned on me a year or so later. E.g. A/B testing soon after buying the Bybees compared to how I perceive them now is different having lost the initial expectation from the hype by the manufacturer. This is more likely to happen if one has no reference point to gauge with. Because after an improvement is also a change. I have over time realized that, that reference point for accuracy is live music and not another higher end system.

While comparing between systems or before/after an upgrade, it is often helpful to isolate each instrument mentally and decide if a saxophone's sound is close to a real saxophone, likewise for other instruments and voices. To this point I very often find judging the sound of an applause, catcalls and all (of all the things!) to be a better indicator for judging accuracy. Live applause seems to be more layered being densely packed with humans shoulder to shoulder and front to back with each point in the soundscape producing a different frequency and all in a tight midrange.

This is my own technique developed over time about dealing with judging if an upgrade is effective. It will be great to hear and learn from you everybody and especially Steve as he has been voicing his builds for donkey’s years now.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/11/19 at 01:08:22

Learning 6:
Ensure all electrical connections (power and signal in/out) are excellent: I noticed the difference  good quality connections make by chance (well sort of, as this is a no brainer): when I decided to up the power capacitance to 13,500 uF per side during the feasibility phase to ascertain viability my planned configuration, I connected the 3 large capacitors (6800uF, 4700uF and 2000uF ) with ordinary wire that was lying around and as well the connections were temporary without crimping eyelets (in fact with alligator clips), soldering, spring washers under screws etc. (see picture in post #54 on this thread where the capacitors are placed on top of each other with loose dangling wires). Then on successful testing like this for quite sometime I made things permanent (see picture in post #86) viz heavy gauge Duelund wire, crimping eyelets, spring washers under screws, soldering, the used of Stabilant 22 on connectors etc. Just improving the workmanship as far as connection quality improved the SQ especially in the bass area. This turned out to be a good test for demonstrating what connection quality can do. In the first instance the connections were temporary hence not much effort was spent on them while in the second case no holds bar connections were made: I can categorically say the difference quality connections made was enough to be noticeable without straining to find if in fact there is an improvement.

On that note I think the application of “contact enhancers” for power supply connections like IEC, power capacitor screw connections and as well for the signal pathway like RCA jacks, speaker binding post, tube pins help more in preserving the contacts from oxidizing over time more than just improving the contact quality. The former benefit more than the latter. In fact I could not discern before/after difference for contact enhancers i.e. was too small to gauge properly. I use 2 types of contact enhancers: Stabilant 22 for the power supply path way e.g. IEC prongs, and power capacitors and Craig Doxit Gold for low power signal type connections like RCA, speaker jacks and tube pins. These compounds more importantly prevent the contact surfaces from oxidizing over time thereby resulting in a reduction of the coefficient of electrical conductivity across the connection with every passing month.

Another point is w.r.t. soldering. I use 4% silver solder and before soldering ensure the there is a physical mechanical connection (twisting together and/or crimping) , then applying the solder to only a portion of the connection the other portion left mechanically in tight direct contact with each other without solder in between.

Another best practice: heat is the worst thing for capacitors life expectancy. It affects the capacitors dielectric medium. So when soldering capacitors draw away some of the heat input by applying an alligator clip with a bare long copper wire connected to it between the solder point and the capacitor.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/13/19 at 02:26:13

Expanding on contact quality mentioned in the above post.

This is the reason for my resulting in dumping all attenuator bar one in the entire audio chain (have one at source equipment only) as for me they are the single largest cause of electric pathway degradation. The wiper leaf spring force attached to the knob spindle has to be deliberately designed to be inadequate (from conduction point of view) to allow easy turning of the knob by weakest of fingers in a given population (male, female, adult, teenagers, children) i.e. if I were designing one I would design it such that a kid (just because an adult may not want to be separated from the cozy chair and askes his kid to turn it for him). Because as a designer I know lay people are not thinking of signal conduction but "who is that moron that designed it to make it so hard to turn". The effect of inadequate spring tension is like not tightening the screws tightly on the capacitor connections. Compounding this weakness in contact integrity is that the attenuators are in the signal pathway - the most delicate, fragile and sensitive of all the electrical currents flowing within an amp. Had they been in the power supply circuits instead the shear magnitude of the current would have bamboozled through this weak connection but alas it has to be in the weakest and the most sensitive pathway.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/17/19 at 12:36:11

More on the impact that enhanced electrical contact make. This is a nice one.

Here are some pictures of my dismantled 19 year old Yamaha DSP-A1 7 channel home theater amplifier that I absolutely love. It was Yamaha's  Flagship HT amp at that time was a reference amp by which all other HT amps were compared to. I still prefer it compared to modern day amps ATMOS and all.

I recently completely dismantled the amp one PCB at a time, cleaning each board meticulously with vacuum and light air pressure on the PCB surfaces, the gold edge connectors (male and female) with an eraser and electro clean (carbon tetrachloride) and applied Craig DeOxit gold to the connectors. There were about 15 PCB boards in all large and service different purposes. The intent of the overhaul was to removed all traces of dust on the surface of each PCB paying special attention to the dust between what seem like 100 or so micro connectors on all four sides of each IC (Integrated Circuits chips) and there are many of them. I think you know what I am talking of. These connections from each of the IC's to the board are so small and so close together (0.01 mm apart) that when dust settles between them it causes unintended micro currents to flow between them kind of partially bypassing the designed intended paths through the circuit board, thereby affecting performance.  

This is such a complex amp that I took 2 days to do it all.

Also I inspected each PCB board and found on one of the boards that there were hairline cracks (like 30 of them) on the pin to board solders and these pins are about 0.5 mm apart – slightly better than IC connectors. I soldered the pins back. But boy soldering anything inside a point to point amp like the ZMA or CSP3 is cake walk compared to soldering the close proximity pins on a PCB that is designed to be done by robots. The picture of the lone PCB (upsidown) shows the pin solders that had micro cracks.

As well all RCA connectors and speaker jacks were thoroughly cleaned one by one inside out with electro clean and then Craig's DeOxit Gold applied to them.

The Volume potentiometer and the program selector switches were also flushed with electro clean spray and spray version of Craig DeOxit applied to the internals of the pots.

While at it I also replaced the power cord and fuses with audio grade ones.

There are no words to describe the improvement. So I'll just exclaim. Wow! Wow! Wow!

Well I explain: movies on my 7 speaker surround sound system are on a different dimension now even though it was very very good before the clean up. I find that sound plays a larger part than vision (the large screen UHD TV) in ones movie immersive experience. Truly sound rules over visual effects. I am not discounting the TVs influence and needless to say having both good sound and a good TV will be even better. But for immersiveness sound subliminally enhances the experience.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/17/19 at 12:40:35

PCB that had micro cracks on the solder pins on both the top edge and bottom edge pin lines. Soldering these without shorting the adjacent pins was something else. On the other side of the PCB are the micro LEDs (dot matrix) that gives information on the front display so they heat up a little bit causing the pins to expand while running and contracts when turned off. The many on/off thermal cycling over 19 years caused the solders to fatigue and crack.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/22/19 at 21:29:52

Learning 7:

This topic is on burn in period.

As you know in the past 3 years I have done numerous component and device changes and thus had many opportunities to note how much burn in time is required for a new device or component to stabilize to an improved SQ stable state. I found that the majority of changes due to burn in happen in the very first half an hour. Then it continues on a time scale that is logarithmically less and less for the next 2 or 3 times the device or component is started up and run. So, in terms of number of hours in total I can reliably say my experience is that I cannot discern changes/improvements after 6 to 10 hours in total and that’s being generous. This I found is applicable for everything from vacuum tubes, to capacitors, to resistors, diodes to whole devices.

I wanted to figure out why burn in causes a changes in SQ and wondering if the answer to it might be more objective than to subjectively claim that a certain burn in period is necessary. After much thought I am inclined to think it is because of metallurgical changes that the metal undergoes on being heated on powering up since nothing else e.g. geometry of the components changes.

Consider the burn in of a vacuum tube (applies to other components as well – capacitors, resistors etc.), within the first 30 minutes of powering up the temperature will have reached the operating temperature from initial room temperature. The internal temperature of the plate, cathode and grids is I estimate roughly about 300 C (572 F) to 600 (1112 F) depending on their proximity to the filament. while the filament is about 3000 C (5432 F) (because the colour of the filament for that material (tungsten) is an indication of its rough temperature, e.g. if it glowed white instead of red (infra-red) it would be even hotter).

It is well know in the wider industrial world that heating metals brings about metallurgical changes at the molecular and crystalline level. Heat treatment is in fact required by national standards and codes such as ASME for critical applications to get the desired properties in metals: malleability, ductility, hardness, toughness, fatigue life…..

Coming back to the audio, this heating on powering on relieves internal locked in stresses that have resulted from cold working the metal (cathode, anode, grids, filament) i.e. bending and hammering to form the plate/grid/cathode shape during the manufacturing process. The raising of the temperature to those levels will cause intra-granular changes in the microstructure of the metals. I believe it is these metallurgical changes and the resultant stress relief that causes these improvements during the burn in period. However these molecular level changes happens largely the first time the device is brought up to its working temperature. Those stress originally caused from the cold working process, do not come back unless the metal is worked on again. This theory also supports the shorter period I am actually seeing that is required for burn in.

The only thing that happens further after 5 to 6 hours is the slow process of aging associated with thermal cycling resulting in fatigue failure and slow oxidation (in spite of the vacuum conditions within the tube) and finally the tube fails and its time for new tubes, capacitors etc.

I now after much experimentation and observation feel that manufactures tout 400 hours of burn in to avoid returns and it’s a way of guiding our expectation that perhaps its not good enough now but will get better in the next 100 hours and the next 100 hours and the next and before you know it its 6 months from the time that device was bought and we lost the initial reference point to decide if in fact there was a improvement so we just assume so because that's what they said so or we move on to the next thing that has caught our fancy.

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 08/22/19 at 22:37:03

Your burn in take is cynical but I suspect correct.  For myself, I lose my reference super fast and despite things being improved, I start to think it doesn't sound as good as time goes by as I get used to the new normal.  Capacitors ought to be different than tubes since the materials are more "organic" and presumably flow with heat.  Do you find the same 5 to 6 hour window for them?

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/23/19 at 00:35:20

On re-reading the last paragraph of my explainaiton I admit it came out that way. But it was not meant to be cynical. Just trying to figure their motive as the figure of 400 hours does not match my experience by a large margin. I wanted to figure out if there is any other reason that figure might be touted. My reason could be wrong that is why I said I feel that that is the reason they are quoting that figure.

Regarding Capacitor burn in. I found the same period of 5 to 10 hours applies. Sure the dielectric medium which btw may or may not be organic (not all are beewax and oil based). But in any case I am not talking of the dielectric medium but talking of the positive and negative plates. In high end capacitors there are yards and yards of copper, silver or metalized films (tightly coiled) within so still the same applies. The operating temperature is not even close to that of the tubes agreed but than again there is far less - if any - cold working performed on them during their manufacture as well the plate thickness is a few microns for the low voltage ones and power caps higher voltage and current ones will have thicker but still a fraction of a millimeter plates. So in my opinion do not require hundreds of hours of burn in.

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 08/23/19 at 00:47:16

Even if you were being cynical, I didn't mean it as a fault.  There is more snake oil than snake these days.

I personally concur with your short burn-in findings.  But I always figured it was my lack of discernment.  The metallurgy explanation makes a lot of sense to me.  Do you feel the same way about ICs and other low heat devices?  Do they burn-in at all?  I don't personally hear a change with time for these kids of things.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/23/19 at 01:18:46

I think ICs themselves being silicon wafers in PNP or NPN junctions will not require burn in. Besides these chips operate at less than 5 volts DC. But the ICs are usually not in isolation there are always capacitors, resistors of various kinds on the same board so that device as a whole will require some burn in. Do not forget the transformers within SS devices with miles of wire with varnish insulation those will require burn in the most, though again I have a hard time with 400 hours.

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 08/23/19 at 01:31:44

Sorry, I used IC to mean interconnect cable and not integrated circuit.   :-[

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/23/19 at 02:10:54

That was funny, I went off on a tangent on a completely different subject.

Interconnects (IC), I have a slightly different take on. They call it burn-in. But to me burn-in in the true sense does not apply here as the voltage and currents are so very small that the wire metal and the insulation for all practical purposes is not affected. That is why you and I do not notice a change. With years there is a change in SQ but that I think it is not primarily because of burn in but due to aging the metal and insulation undergoes chemical changes being exposed to air.

But what matters for IC is the wire quality (material and purity) and the insulation which together tends to act as a capacitor. So choice of ICs is more of a consideration than burn in. A good IC will sound good from day one.

Speaker wires are exposed to higher voltages than ICs so there might be some burn in but again not so much to even think of it. Again I think here choice is more of a consideration and if its a good wire it will sound good from day one, with minor changes over time if at all and these change are not worth talking about. Again aging applies here as with the ICs.

I noticed power cords do change the sound with time. It makes sense too that power cords undergo burn in and will be better with time say over 50 to 100 hours - not 5 or 6 hours definitely. But even here choice of a cable really matters more than burn in (wire quality and insulation) but burn in does play a small part more than for an IC or speaker cable.

N.B: Ageing makes the wire worse off (oxidized copper or silver will conduct less) but is measured in years rather than hours where as burn in improves its qualities but happens over hours.

Title: Re: ZMA - comperhensive upgrade complete
Post by Jeff of Arabica on 08/23/19 at 05:20:45

I definitely feel the burn-in phenomenon is "type-specific."  You raise some interesting points of discussion with regard to voltage and burn-in effect.  I can't say that I disagree that  the long stated burn-in periods  from vendors are a product of sales/marketing to exceed the customer's trial period.  I have often been suspicious of these prolific claims.  

One thing I do want to comment on has to do discussion on oxidation.  Copper Oxide (CuO) is a very poor conductor.  If you have in your system, raw exposed copper, then you must be aware of CuO and rid it as it develops.  It is not a great conductor, so as you consider skin effect, CuO is the enemy.  

Silver on the other hand does not share the same inherent handicap.  Silver Oxide (Ag2O) is in fact a great conductor.  That said, one need not worry about their raw and exposed silver cabling oxidizing like is the case with copper.  Ag2O is a great conductor and scientifically proven to conduct as well as Ag.  

What does this mean?  Well, that depends.  If you are using interconnects or speaker cabling with raw metals that are exposed to oxygen, then it is important to know if the Oxide of that metal type will have a detracting effect on the signal, or not  Ag20 is nothing to worry about.  

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 08/23/19 at 16:11:46

That is my understanding about silver oxide as well.  My silver speaker wire ends are quite tarnished.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/23/19 at 21:17:03

Jeff, aging is measured in years anyways v/s burn-in which is in hours so aging is less of a consideration.

I have not checked the resistivity values of Ag v/s Ag2O I'll take your word that they are equal. To me they should be different perhaps not by much but I being a nitty gritty person and wanting to squeeze every ounce of performance that even a small difference between the two will drive me to do something about it. That is why I buy 6N or 7N silver wire instead of 5N or less. The difference in conductivity here is even less I would think than oxide/no oxide on silver, but I still do it because for interconnects and internal signal wires from the RCAs to the input tubes (mentioned in one of my earlier post on this thread) I like to preserve the delicate input signal as much as I can.

Having said that both gold and silver being noble metals do not oxidize unlike copper. The tarnish you see on silver is more of a sulfide than oxide. Sulfide I believe is a bad conductor therefore e.g. RCA connectors are not usually plated with silver but gold (gold being a more noble of the two metals resists reaction with chemicals in the air).

You made a good point on metal inside of insulation being oxidation free. That is a good discussion point. My take is oxidation happens not only to exposed wire but also to the insulated portion (at a much slower rate) of the wire. This is because of permeability of the insulation. If you have any spare 10 years or more old wire strip off some insulation and you will see that there is an oxide/sulfide layer or what ever have you with the pollution in the air these days. If you use a sand paper on it you'll than expose the parent metal.

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 08/23/19 at 22:50:11

Interesting.  I've read consistently that silver oxide conducts better than silver itself but no where that silver doesn't oxidize and that the tarnish is, in fact silver sulfide, which is a poor conductor.  It just goes to show that "information" on the Internet can be very misleading.

I'll clean my cable leads and try some Graphene contact enhancer on them.  Maybe this will protect against future tarnish and maintain a better contact.

Title: Re: ZMA - comperhensive upgrade complete
Post by Jeff of Arabica on 08/23/19 at 23:10:58

What we all experience with exposed silver is Oxide. Oxide is a chemical compound formed when silver and oxygen react. That is the tarnish on our untreated, exposed silver cabling and interconnects.

And you are correct Archie, research has shown that the oxide of silver is actually a better conductor than pure silver.

As far as silver sulfide, that would be extremely abnormal. Sulfur is not generally present in ones home. If it was, you would smell it!  :-[  Silver Sulfide can only form when silver is exposed to sulfur and they react, forming the compound Silver Sulfide.

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 08/23/19 at 23:29:14

Jeff, everything I just looked up said that silver tarnish was silver sulfide.  Can you post any links to clarify this?  Here's a typical one that I found:

There's also Wikipedia.

Title: Re: ZMA - comperhensive upgrade complete
Post by Jeff of Arabica on 08/23/19 at 23:41:28

Ha! I stand corrected.  Bonnie is right in that the tarnish is in fact a Sulfide.  I just learned that it does not take much environmental sulfur concentration to form the tarnish on silver. Tarnish on  copper is in fact a product of oxidation.  

I guess there has been too many decades since my last college chemistry course  ;D

Thanks Bonnie and Archie.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/24/19 at 00:16:18


I had to waft away a few layers of foggy memory myself.


Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 08/24/19 at 00:41:53

Thank you guys!  What's amazing is that every site I've seen about using silver wire sights the fact that silver oxide conducts better than silver.  Yeah, so ... ?

Title: Re: ZMA - comperhensive upgrade complete
Post by Jeff of Arabica on 08/24/19 at 04:52:09


I had to waft away a few layers of foggy memory myself.


No kidding...LOL.  And Chemistry was my favorite subject going into college.  

That, and I am in an industry where oxidation is our product's #1 enemy, so I guess I am jaded. Sorry Oxygen.  I still love you very much and need you dearly in my life.  Damn you Sulfer, coupled with HsO.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/24/19 at 23:29:11

Jeff, Archie:

In the bargain we (well you both) might have discovered a brand new method for enhancing audio performance further. If silver oxide is a better electrical conductor than pure silver what if we deliberately accelerate the oxidization of silver? Because silver is resistant to oxidation in air what if it is exposed to higher concentrations of oxygen, say the oxygen used by medical patients or if it is available from somewhere else?

But for the life of me, I am finding it difficult to find the actual value of resistivity of Silver Oxide unlike you Jeff, Archie.

For pure silver it is 1.59 × 10−8 Ωm at 20C what did you find the value is for Silver oxide?

If the value is lower as quoted by a accredited lab or research paper I might try exposing a pair of silver cables to higher levels of oxygen if I can find it easily.

I mean we buy cryo treated cables and all kinds of things so why not expose silver wire to concentrated oxygen if that will squeeze more performance?

Sounds crazy now, even far fetched, but you never know it might be the next rage just like cryo treatment has now firmly established itself.

Title: Re: ZMA - comperhensive upgrade complete
Post by Archie on 08/25/19 at 00:06:28

I did find this paper that seems to list conductivity for silver oxide but damned if I understand any of it.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/25/19 at 00:58:15

Sorry to report that, that research paper does not apply to our discussion. It applies to electron beams and their propagation (conduction) in optical media with varying thicknesses of Ag2O applied to the surface not really to transmission of electricity in conductors such as wires.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 08/26/19 at 23:52:08


Now that I am essentially running two of the Torri II mono's in a single chassis with KT120 tubes (these tubes are glorious - the ease with which they drive my 89dB speakers (24Hz to 150 kHz) is something else compared to KT88s) I cannot but help recommend to you to start another product line: ZMA II with 60W output.

Currently you have the ZMA line and than there is a huge price difference for the next product up, the Torri II mono pair. The new 60W ZMA II with KT120 as the primary tube (it is designed around), would nicely fit between these two extremes, I think.

Besides the price the other advantage for buyers is the use of only one audiophile power cord which is a huge saving in itself.

Something tells me you'll sell more of these than the Torri II monos because with 60W at one's disposable there are less restrictions on the type of speakers one can use and being at a lower price point (due to optimization of material - one chassis, power supply peripherals) and yet with performance rivalling that of the mono's will help (depending on the parts chosen off course).

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 09/09/19 at 00:35:24

Learning 8:

I have found that turning ON the ZMA about 15 to 20 minutes before actually starting to play music is the quickest way the amp reaches its sweet spot.

I have consistently found that if I start playing music right away it takes longer to get to the sweet spot and the louder I start playing music from the very initial time the power is turned on the longer it took to reach a point where the SQ stabilizes to that fantastic level.

This phenomenon may be unique or more appropriately exaggerated in my ZMA because I have an inordinate amount of power capacitance: to remind every one it is 13500 uF per side.

On another note the experience with adding capacitance has affected my belief in it so much that I have now ordered extremely fast oil capacitors that I am going to add to the 13500 uF. I am limiting these oil caps to only 70 uF (even at 70 uF they are huge in size) as the objective here is not to add further storage of power (diminishing returns on that front) rather to compliment the already large capacitance currently present. By adding even more speed to the “power package” to deliver the very first micro burst of supply power as and when demanded before the other larger capacitors take over.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 09/13/19 at 23:28:06

The Obbligato Film oil 70 uF caps have arrived. I was surprised at the physical size of the capacitors. Inspite of just being 70 uF they are 5 inches in height and slightly over 2 inches in diameter !

I have not installed them yet but just thought a picture along side my largest cap the 6800 uF Mundorf Mlytic 4 pole caps which themselves are huge would be of interest. It may be hard to see in the picture being of the same color as the Mlytic cap in the background.

Cannot wait to install them and find out the results.  I don't expect any spectacular change though but more nuanced. I believe it is small details such as these that will contribute to making my supercharged ZMA even better especially when playing fast dynamic music. Let's see ….

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 09/27/19 at 22:12:16

Learning 9:

Obligatto Film Oil Power caps install:

These are true metal (aluminum) film capacitors filled with oil. Not pseudo film caps such as metalized polypropylene. Copper or silver film would be better but the price increases substantially and for power supply silver would perhaps be an overkill unless you have money to burn. I must confess buying the Obligatto caps was by chance. I bought these only because these 70 uF ones were 50% off in price and thought why not try them out.

For small 70 uF capacitors they are pulling above their weight. I am tired of extolling the benefits of this and that, but these definitely are making the highly modded ZMA even better. Had I experienced what I am now, I would have bought the largest Film oil cap(s) that would fit in the capacitor opening in the ZMA top plate when I first replaced the large red Mallory 2000 uF power capacitors with Mundorf Mlytic 4700 uF HP+ 4 pole capacitors. These turned out to be even better than the Mundorf Mlytic’s 4 poles for imparting added dynamism.

I am still wrapping my head around as to how the relatively small value 70 uF Film Oil caps brought more air, depth, timing and agility to an already fantastic output.

Which led me to do a bit of experimentation:
To zero in on the contribution from the film oil caps and get acquainted with their properties I disconnected all of the 13500 uF of capacitance and only left the 70 uF oil film caps in the power supply. Intent was to enable comparison to the 13500 uF of electrolytic capacitor aggregate setup that I was well familiar with by now. I can say that this was perhaps the biggest learning for me thus far. For almost all of the other upgrades mentioned in earlier posts above I would say they came out as expected with no major surprises as they were careful calculated buys (except perhaps the Bybee purifiers).

These oil film caps at only 70 uF improved dynamism better than all the 13500 uF electrolytic caps put together even considering the fact that mine were the top grade 4 pole low ESR/ESL 4 pole Mundorfs Mlytics. These relatively small oil film caps resulted in the timing being more to the point. There was a loss of air and extension and noise floor increased. I think this is because of the low value of capacitance them being alone. I am certain if I had oil film caps with a total of 13500 uF or even 3000 uF the results will outstrip the 13,500 uF electrolytic caps.

I than installed the 13500 uF electrolytic capacitor aggregate back along with the 70 uF oil film capacitors. This setup was the best, better than either alone. Together the background got lowered considerably also besides enhanced airiness and that all important timing improved palpably.

As mentioned earlier but worth repeating with perhaps more detail and perspective. I wish I had discovered these earlier, before I purchased the Mundorf caps (6800 uF and 4400 uF costing about $800 in all) I would have instead bought the largest oil film caps that I could fit. The oil film caps are 3 times the physical size compared to an equivalent capacitance electrolytic cap. I do not think I could fit an oil film cap greater than 600 uF in the same place as the original 2000 uF Red caps. But I believe 600 uF of oil Film caps would be awesome.

In hindsight, I now think there is no point in having large capacitance caps if they are slow (high ESR). Music is all about timing. Fast caps do not allow the circuit voltage to sag during instantaneous demand spikes while the music is being played (a deep bass note here and there, rhythmic bass notes and other demands such at another micro instant more than normal number instruments / voices output higher demand notes together). When the amount of instantaneous required power supply is not forthcoming at the instance it is needed that is a lost opportunity and is fleeting and timing of the music is affected due to circuit voltage droop. By the time the slower electrolytic caps (even though they may be very large) respond the train has already left and having missed the train the power supply now is always playing catch up thus affecting timing. Mind you the Mundorf Mlytic 4 Pole caps are way faster than the original stock ZMA red Mallory caps and resulted in improvements mentioned earlier in this thread but these oil film caps are in another league in terms of speed. The very best would to install very large fast oil film caps and the larger the capacity and fast the caps are gives greater isolation from the grid (the noise floor becomes eerily quiet) while not causing a depression in circuit supply when demand increases due to faster charging/discharging cycles.

Now I can say that ideally all of the power capacitors should be oil film type. But that would mean capacitors physically the size of the whole footprint of the ZMA amp (I think) since film oil capacitors size  to power ratio is very large. So given that space is a constraint, a hybrid mix of oil film and electrolytic caps would be the solution. This way the faster oil film caps will serve the initial micro burst of power demand while gargantuan electrolytic caps can than take their sweet time continuing to maintain the downstream circuit supply.

I’ll slowly be adding more film oil caps to my capacitor aggregate in the power supply, perhaps even remove the red Malory 2000uF caps to accommodate the new caps.

Sometimes good things happen by chance.

Title: Re: ZMA - comperhensive upgrade complete
Post by Steve Deckert on 09/28/19 at 04:59:38

I have always noticed there is some correlation between a capacitors performance and it's physical size.  That 70uf cap probably has the nuts of 700uf of electrolytic or more even though it would be hard to measure (unless you use your ears of course).

Even when voicing my amplifiers, a physically larger film cap of a smaller value can often be used instead of a physically smaller film cap of a larger value and yield the same results.


Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 09/28/19 at 22:54:41

I do not have as much experience with swapping different types and sizes of capacitors as you Steve (not even close), but now that you mention it I can recall feeling the same: physically larger film caps have more whoomph than smaller ones of the same capacitance value e.g. in the above case of the Obligatto Film oil cap install and earlier when I installed the 47uF Mundorf Tube caps in place of equivalent capacitance F&T electrolytic caps.

In the power circuit of an amp I generally tend to go for the largest capacitor value based on what will fit physically and quote the size in terms of capacitance i.e. the largest value possible in order to achieve battery like power supply conditions. But also the Time Constant T (tau) of a capacitor is perhaps more important in the power and signal circuits. Where as very specific capacitance values are required in the noise filtration circuit (which of course is a subset of the power circuit) to filter out specific frequencies of noise (e.g. 120 Hz noise from a fast full wave solid state diode based rectifiers or very high frequencies from switching power supplies from other equipment in the house or neighbors or an electric arc furnace in a foundry in the town somewhere).

A lot of experimentation and expense can be avoided if manufactures of capacitors meant for house hold equipment give extensive specification details including the time constant and ESR/ESL values. Very few if any do that. They generally only specify the capacitance value, the temperature rating v/s life in hours and some times if ever the ESR/ESL values and almost never the Time Constant (Tau) of a capacitor and talk in terms of sweetness, mellowness, warmness and other adjectives. I must admit these adjectives do not help me at all in buying decisions as these are subjective even to the extent that someone's sweetness is another person's mellowness. I also have a hard time with what sweet , warm sound etc,.is.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 10/27/19 at 22:53:08

Further improvement in the ZMA power supply:

The itch to get more out of the ZMA continues.

For the longest time I was thinking the power rocker switch was a weak spot in my heavily upgraded ZMA power supply chain. See upgrades to Power supply mentioned earlier in the very first post in this thread for stuff already done to the power supply before. More so given that my souped up ZMA is now drawing more current: from 4 to 5 Amps before to 7 to 8 amps I felt I needed to do something about it. I was hesitant up until now mainly because to access the original power switch was difficult being buried underneath a mass of capacitors, resistors, wires and bus bars. All these needed to be cleared and then re-assembled for this task.

Rationale for this upgrade:
Switches and circuit breakers over time tend to pit and carbonize at the contact points. This is because when the switch is opened (when turning a device off) as the gap between the contacts is increasing as it travels from fully closed to fully open position there is arcing between the moving contacts until the gap become large enough as it approaches the open end stop to the point that the arc cannot jump across the contacts. The larger the current the more the arcing and slower the opening the longer the arc is sustained. A bit of learning from the electrical industry at large: Industrial circuit breakers that handle thousands of amps of current have arc chutes, air blaster and for even higher current handling the contact points are enveloped in pressurized SF6 (sodium hexafluoride gas) to quench the arch and are also extremely fast as the circuit breakers open (blasted open by extremely high pressure (> 6 MPa) nitrogen). This arcing causes pitting on the contact surfaces thereby progressively decreasing the effective contact area over time. In turn this decreases current flow during subsequent normal operations and is worsened by the fact that the arc also causes very slow (over years) carbonisation of the contacts.

What is done:
In light of the above. I installed a heavy duty double pole (20A each pole) toggle switch (DPST switch). This particular switch (Russian heavy duty old world type) was chosen due it being mechanically fast and and as well makes and maintains forceful contact. I installed the DPST in parallel with the original 15A (I think) rocker switch. I wired both poles in the DPST such that current flows though both poles and also thorough the original rocker switch making the switch combination able to handle 55A at 250V AC. Far in access (@ 7 times) of the steady state current draw but this huge current handling ability should hugely handle large micro burst of current without chocking.

Proof of the pudding is in the eating:
I can now easily test the efficacy of this upgrade because of the ability to power the ZMA in various permutations and combinations i.e. using the original rocker switch only, or only the new double pole toggle switch or both together. In trials the consensus is that when demanding music is being played and this so at loud volumes the new DPST switch and the original rocker switch when used together as compared to the new double pole used singularly has no perceptible difference in the sound dynamism. But when the double pole switch is compared to original toggle switch each used singularly the difference is more than subtle. The double pole toggle switch wins handsomely, the sound quality difference is more perceptible especially with demanding music (heavy metal fast music – not that I listen to heavy metal much – used only for testing). Though not so perceptible with lighter music it feels more liberated with the use of the new DPST.

Usage methodology:
To minimize wear and tear of silver contact surfaces (from arcing) on the new double pole switch (to keep its contact clean longer) I first switch on the original rocker switch and than when the initial inrush of current subsides I bring in the double pole switch. For turning off I first turn off the new double pole switch and than the original rocker switch. This way the DPST is opening/closing with minimal arching due to the parallel pathway of the original rocker switch.

Cost of upgrade: $20 ….. worth it.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 11/15/19 at 02:27:39

An attempt to lower the internal temperature for longevity of capacitors.

Patterned holes drilled in the bottom panel - see picture.

Was not comfortable with the fact there was no ventilation of the internal space. Especially as the base is made of wood which is a poor conductor of heat compared to a metal enclosure. Most audio equipment has metal enclosures, as well as ventilation slots all around.  The metal enclosure dissipates heat through conduction (along with internal heat sinks) and the ventilation slots dissipates heat by convection.

Those look like they are too few holes to make a substantial difference but there was no point as the openings at the top were limited to those around the two large capacitors where they protrude through the top plate. The cross-sectional area of the sum of the holes in the bottom plate is about 2 times the circumferential gap around the two large capacitors at the top plate. The 4 pole 6800 uF Mundorf caps are about 2 mm smaller in diameter as compared to the original red capacitors which helps with the ventilation.

I do not think this will decrease the internal temperature by much (have not taken before and after temperature measurements) but it is better than being sealed, I thought.

Title: Re: ZMA - comperhensive upgrade complete
Post by BAndrade on 03/22/20 at 02:45:48

Hi folks,

Just thought I'll report that my ZMA with all that has been done is doing well. No issues in spite of it pumping out 60W per channel for more than 6 months now.

Haven't done any more upgrades on the amp since the last post in November of last year, as it is saturated on that front besides other non-audio stuff is keeping me busy.

The next "upgrade" I am planning on is trying out KT150 output tubes in place of the KT120 that I have been using for the last six months or more. I briefly tried KT66 and also KT88 one evening in January. As expected there was loss in bass but also midrange and treble. I feel that the added bass with the KT120s carries/influences the higher frequencies in the air between the speaker and listener. There is a symbiotic relationship between all the audible and beyond audible frequencies: it seems they help each other out.


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