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ZMA - comperhensive upgrade complete (Read 2306 times)
BAndrade
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ZMA - comperhensive upgrade complete
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
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BAndrade
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Re: ZMA - comperhensive upgrade complete
Reply #1 - 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
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BAndrade
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Re: ZMA - comperhensive upgrade complete
Reply #2 - 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
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BAndrade
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Re: ZMA - comperhensive upgrade complete
Reply #3 - 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.
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BAndrade
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Re: ZMA - comperhensive upgrade complete
Reply #4 - 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.
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Jeff of Arabica
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Re: ZMA - comperhensive upgrade complete
Reply #5 - 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   Wink  

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!  
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ZMA//Zen Ultra//Rachel//Super Zen//Taboo MKIII//PS Audio DirectStream DAC + Memory Player + P10//Muse Phono Stage//London Decca Reference//Dynavector DV-507 MKII//Zen Head//SonoruS Reel-to-Reel w/ tube playback pre-amp//Omega SAHOs//DM946//Oppo UDP-205
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HockessinKid
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Re: ZMA - comperhensive upgrade complete
Reply #6 - 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.

HK  
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Lonely Raven PC (or) TEAC PD-600H > ZDAC2 (or) Nottingham Interspace (heavy platter) TT w/ Dynavector 20X2LO + P75 MKII phono pre > ZROCK2-25 > CSP3-25 preamp > Zen Mystery Amp > Omega SAHO XRS speakers > ZenWave Audio, TWL, & Acoustic BBQ cables.
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BAndrade
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Re: ZMA - comperhensive upgrade complete
Reply #7 - 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.

Cheers,
Bonny

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Re: ZMA - comperhensive upgrade complete
Reply #8 - 04/07/19 at 16:46:35
 
Bonny,

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.

HK



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Lonely Raven PC (or) TEAC PD-600H > ZDAC2 (or) Nottingham Interspace (heavy platter) TT w/ Dynavector 20X2LO + P75 MKII phono pre > ZROCK2-25 > CSP3-25 preamp > Zen Mystery Amp > Omega SAHO XRS speakers > ZenWave Audio, TWL, & Acoustic BBQ cables.
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BAndrade
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Re: ZMA - comperhensive upgrade complete
Reply #9 - 04/07/19 at 18:52:36
 
HK,

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.

Bonny

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Re: ZMA - comperhensive upgrade complete
Reply #10 - 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.

HK
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Lonely Raven PC (or) TEAC PD-600H > ZDAC2 (or) Nottingham Interspace (heavy platter) TT w/ Dynavector 20X2LO + P75 MKII phono pre > ZROCK2-25 > CSP3-25 preamp > Zen Mystery Amp > Omega SAHO XRS speakers > ZenWave Audio, TWL, & Acoustic BBQ cables.
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BAndrade
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Re: ZMA - comperhensive upgrade complete
Reply #11 - 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.
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Re: ZMA - comperhensive upgrade complete
Reply #12 - 04/07/19 at 20:39:05
 
Here is a picture of my ZMA taken before this process began 2 years ago for comparison.
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Re: ZMA - comperhensive upgrade complete
Reply #13 - 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.

HK
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Lonely Raven PC (or) TEAC PD-600H > ZDAC2 (or) Nottingham Interspace (heavy platter) TT w/ Dynavector 20X2LO + P75 MKII phono pre > ZROCK2-25 > CSP3-25 preamp > Zen Mystery Amp > Omega SAHO XRS speakers > ZenWave Audio, TWL, & Acoustic BBQ cables.
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Re: ZMA - comperhensive upgrade complete
Reply #14 - 04/07/19 at 21:01:23
 
HK,
The seller I bought from in Germany has no 4700 uF Mlytic caps  currently.

But he has 3300 uF Mlytic caps.

https://www.ebay.com/itm/MUNDORF-MLYTIC-MLSC-HP-3300-f-500VDC-Kondensator-4-pol-...

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.

https://www.ebay.fr/itm/223462562200?rmvSB=true

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Re: ZMA - comperhensive upgrade complete
Reply #15 - 04/07/19 at 21:27:55
 
Fantastic work. Envious skill set you have, thanks for explaining everything in a way that was accessible.

JD
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Re: ZMA - comperhensive upgrade complete
Reply #16 - 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
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Re: ZMA - comperhensive upgrade complete
Reply #17 - 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.
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Re: ZMA - comperhensive upgrade complete
Reply #18 - 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.
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Re: ZMA - comperhensive upgrade complete
Reply #19 - 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
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Re: ZMA - comperhensive upgrade complete
Reply #20 - 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.

Cheers
BonnyA
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Re: ZMA - comperhensive upgrade complete
Reply #21 - 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. Grin Grin

Regards
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Re: ZMA - comperhensive upgrade complete
Reply #22 - 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.
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Re: ZMA - comperhensive upgrade complete
Reply #23 - 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

Result:
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!
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Re: ZMA - comperhensive upgrade complete
Reply #24 - 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.
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Re: ZMA - comperhensive upgrade complete
Reply #25 - 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.
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Re: ZMA - comperhensive upgrade complete
Reply #26 - 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.
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Re: ZMA - comperhensive upgrade complete
Reply #27 - 04/24/19 at 01:21:17
 
Quote:
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.
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Re: ZMA - comperhensive upgrade complete
Reply #28 - 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.
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Re: ZMA - comperhensive upgrade complete
Reply #29 - 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.
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Re: ZMA - comperhensive upgrade complete
Reply #30 - 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.  
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Re: ZMA - comperhensive upgrade complete
Reply #31 - 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."

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Re: ZMA - comperhensive upgrade complete
Reply #32 - 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.
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Re: ZMA - comperhensive upgrade complete
Reply #33 - 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.
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Re: ZMA - comperhensive upgrade complete
Reply #34 - 04/25/19 at 05:55:51
 
Donnie,
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.
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Re: ZMA - comperhensive upgrade complete
Reply #35 - 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.
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Re: ZMA - comperhensive upgrade complete
Reply #36 - 04/25/19 at 21:16:33
 
I live in Canada.

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Re: ZMA - comperhensive upgrade complete
Reply #37 - 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.
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Re: ZMA - comperhensive upgrade complete
Reply #38 - 04/26/19 at 00:46:08
 
You can still come.  I don't think there are plans for a Northern Border wall ... yet.   Cheesy
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Re: ZMA - comperhensive upgrade complete
Reply #39 - 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.
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Re: ZMA - comperhensive upgrade complete
Reply #40 - 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.
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Re: ZMA - comperhensive upgrade complete
Reply #41 - 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.


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Re: ZMA - comperhensive upgrade complete
Reply #42 - 05/19/19 at 23:00:45
 
Quote:
...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.
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Re: ZMA - comperhensive upgrade complete
Reply #43 - 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.
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Re: ZMA - comperhensive upgrade complete
Reply #44 - 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.
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Re: ZMA - comperhensive upgrade complete
Reply #45 - 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).
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Re: ZMA - comperhensive upgrade complete
Reply #46 - 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.
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Re: ZMA - comperhensive upgrade complete
Reply #47 - 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.
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Re: ZMA - comprehensive upgrade complete
Reply #48 - 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.
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Re: ZMA - comprehensive upgrade complete
Reply #49 - 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.
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