Has anyone experimented or is running their ZMA with the tubes biased lower than 50? What differences have you noticed?

I've recently gone the other direction.  I am running my ZMA hot!  I have a set of Gold Lion KT88's and I am running them at 78mA.  Previously, I was running a set of TJ Full Music KT88's at about 74mA with great results.  

I am liking the KT88's in my ZMA and consequently, I have to run them hotter than other tube types by nature - they simply will not bias any lower.  So, if I want to run a lower bias, I have to swap out with other tubes such as KT66's, EL34's, etc., but they don't sound as good in my system as the KT88's I have.  

Out of curiosity, I've hit the transformers with my infrared thermometer on numerous occasions while the ZMA has been running pretty hard.  The range of temperature readings I get is between 130 and 140 degrees, which is well within normal operating temperatures for any quality transformer.  

With the hotter running KT88's in my system, I am getting better overall output, along with a greater dynamic range.  These tubes, along with my recent power supply mod, I am hearing greater detail, particularly improved at lower volumes.  The instrument separation is dumbfounding.  Ive had this amp for quite some time now and the width and depth of the soundstage, and placement of the musicians/singers is surreal.  The ZMA has always been my jam but running her at higher RPM's with KT88's and improving what I would consider the "throttle response" and "top speed" of this amp with the capacitor mod, I really have zero desire to do anything else to this amp or my system in general.  That "itch" to tweak/add/modify/ is gone for the very first time.  Will it last?  Probably not, but it sure is nice to simply sit back and take pleasure in the music flowing from my system.  

120 is conservative. 130-140 is safe. The finger test is fine and all but depends on one’s pain tolerance. Even at 140 I can touch it for 6-8 seconds. Based on folks I have consulted on this very matter, I have no worries running them anywhere below 80mA.

Of course Steve is going to advise ultra conservative. These amps are under warranty and it is on his dime if  they happen to go out in 20 years instead of 30.  At the end, it’s your amp and you run it how you are comfortable. Based on what I have read and what I been told by a competent and experienced technician, there is no need to fret over biasing up to 80mA - on the ZMA that is.

I don't mean to beat this to death but this is from the ZMA Manual:

WARNING
This amplifier is designed to operate with a 50ma bias on each output tube.
Running higher bias currents for any length of time will overheat the power supply
transformers and could cause pre-mature failure. We recommend no more than
60ma per tube at any point. Running less is not an issue for the power supply but
doing so will reduce the power output of the tubes and change how they sound.
Some will use this technique as an esoteric voicing tool.


This also addresses the original question of this thread regarding lower bias settings.

Quote:


I apologize, but I forgot to point out for anyone interested in using a KT88 with your ZMA, Page 11 of the current ZMA Manual lists the KT88 as an alternative to the KT66.  

For me, the KT88 have bested any other tube type and brand that I personally have rolled in my ZMA, in my system.  I will continue to enjoy this most amazing sound that flows through these very dynamic tubes.

JFC I don't think my question was a difficult one. I specifically asked if anyone was biasing tubes UNDER the 50 mark and their thoughts on that.

Quote:
 

Does that mean what I think it does?  Come on, you ought to expect a certain amount of off topic in these threads.  I'm glad it went this way so we could get some clarification on bias vs temperature.

Off topic and then back to the topic is a Hallmark of this Forum. You won't find any of these moniker's here: 



Spirited debate should be welcomed....as was this discussion (and I learned a half a dozen other things just now). I have had a few spirited posts, with a couple member's myself, in the 17 years I have been on this Forum.  ....and we come back to on TOPIC succinctly.

I make no apologies for NOT liking high sensitivity Speaker's (I run 91/92db @ 1 watt/1 meter).....AND wanting Steve's input about enhancing the ZMA power supply/speed....talk about off topic for this Thread?!

Now, back to Topic.... I agree with J of A....lower than 50...no good.


Thanks Archie, Steve and J of A.....as discussed here and in the ZMA tube rolling Thread....I need to get some KT88'S... .

I see Electro Harmonix quads of KT88s for about $120.  Does anybody have experience with these tubes or EH tubes in general?  They also have a 6550 which is supposed to be compatible but I don't know what the difference is.

This is cheap for a quad of KT88 tubes -- maybe too good to be true?  I don't want to throw away $120 on crappy tubes.

Stone, thanks. That's enough for me to avoid them.  Any thoughts on JJ tubes?  I'm going down the list of inexpensive KT88s on ebay.

While I haven’t rolled any of the JJ tubes, my gut feeling is you will like dynamics the KT88 in general brings to the ZMA.  

Steve intrigued me by the N.O.S. 7027 mention.  I just picked up a set of (10) closely matched RCA brand 7027’s to try.  Wasn’t in the market for 10 of these tubes, but if the results are good, Ill have a complete second set, for when they wear out.  I’m curious how these will bias.

Let us know what you think of those JJ's Arch and I look forward to your opinion Jeff on the 7027's. It is great to have all these options!

I'm going to stick with my plan, but instead, get the cryo Gold Lion KT88's in here soon/first and then the TAD cryo KT66's.

Since, I am not getting back in to low power Amp's...tube rolling input tubes with my stalwart Telefunken inverters with output tube rolling will certainly continue for me.

I've been enjoying my Mullard's ~ Tele's & 6P output tubes so much I have had no desire lately to put my Tung-Sol KT66's in. Need to get those KT88's soon though... .

I might get a couple more pair of input tubes on my radar from Upscale.

Lately, I am enjoying the adjustment of my ZDSD's input volume and output level.....manipulating Redbook CD's for the way better!




~ All NOS Platinum graded Tubes from Upscale Audio (except 6N23P's):

(Great Britain) Mullard 7308/E188CC ~  2 pair (both pair Cryogenic)
(Germany) Telefunken 6922/E88CC ~ 1 pair (painfully expensive/worth it)
(US/Great Britain) Ediswan CV2492/6922 ~ 2 pair (one pair Cryogenic)
(Hungary) Tungsram 6922/E88CC ~ 1 pair
(Hungary) Tungsram PCC88/7DJ8 ~ 1 pair

(Russia) 6N23P's ~ 2 pair/came with ZMA.  





Listening Room:



Room Treatments from Michael Green & my Home Brew


Sony as Transport (DVP-NS57P)
Illuminati D-60 Digital Coax IC ~.5 meter


Shunyata Research Zitron Alpha Digital Power Cord to ZDSD {Significant}


Decware ZDSD DAC / Recorder
***************************************************************
W/Steve's Output Transformer's/kicking to the Curb quite a few superb DAC'S
***************************************************************
(@ -20 Ref Level, 0.0 Input volume and @ 16/192)
~Adjustments made often to Input volume: -.5, -1.0, -1.5 & -2.0 max
~Adjustments made often to Ref Level: -20, -18, -16 & -14 max


WBT-0102Ag RCA Kimber Select KS1030 ~.75 meter


Decware Zen Mystery Amplifier
~BIASED at *56* mA~
NOS/Platinum/Mullard E188CC/7308's in my A12 an B12 Input positions Cryogenic~NOS/Platinum/Telefunken 6922/E88CC for Inverter Tubes~NOS RCA 0A3's & matched Quad/Tung-Sol KT66's or 6P3S-E's




***************************************************
Kimber Select KS6063 Speaker Cable 8ft WBT-0681-Ag Spades
***************************************************
Kimber (new jacket) 8TC ~ to remind me~how good the KS6063 are


Acoustic Zen Adagio - Black Pearl (Modified)
.....enjoying from 8 ohm ZMA Taps


Caintuck Audio Eminence Alpha 15" OB BASS Unit
at 43Hz, with my Velodyne CHT 130 watt plate amp and 0 degree phase
Plate Amp....regen'd clean ~ plugged into P3
Auralex Subdude (a must)
(NOTE ~ Only needed when the recording calls for...Open Baffle Bass has been the best integration I have witnessed when needed and called on)







Acoustic Zen Adagio's x-over's Modified/Full Range with Mundorf MCap Supremes-single Cap to each Tweeter/4.5k cross
(Gutted: 3kHz/18dB/Octave, Linkwitz/Riley Crossovers....with all crappy parts = gone)


ZMA, updated with robust Western Electric Bias/Balance Meter's and new Resistor's ~ Feb/17

XLO Pro Power Cord to ZMA
Shunyata Research Zitron Alpha Digital Power Cord to ZDSD {Significant}
PS Audio P3 Power Plant / Pangea AC-9SE from wall to P3
(Transport and ZDSD, Regenerated/*120*~ Multiwave off...ZMA on High Current Output)
System configured on Floor ~ Townshend Audio CD Seismic Sink deployed & other Isolation devices.

Yes, for sure - variety, Archie.

I put my Tung' KT66's back in today. As much as I enjoy the presentation/way, of detail and very good dynamic's of the 6P's........... the KT66's open back up the SLAM Dynamic and love the fuller output settings of my DAC (ZDSD)!

KT88's, as J of A mentions in his reply #2 & #8.....I got to get the Gold Lion (cryo'd) KT88's in here.

Arch, let us know....cause' those JJ KT88's you have coming, I bet, are no slouches either.

Thanks Steve, on the KT88 new prod recommendation.

I'm in for the 7027 too. Jeff found some RCA NOS. Any recommendation for new production on these? JJ or Tung-Sol?

Nice to have the KT66 back in (in my System/Speakers/Kabling = no edge). However, the 6P's micro dynamic's are to be appreciated.

I am intrigued by the 7027. Maybe, its design provides an advantage over the 6L6. I'm going for a matched quad of the JJ's. Leading edge attack & slam?  ....Look forward to these puppies for under 100 duckets.

...With the leading edge transient attack of the 7027...and its smaller envelope like the 6P's....maybe I get my micro dynamics of the 6P's too? I should..... .    

I love my music and this hobby!

This very right now? Jammin' to the macro' of the KT66 Tung-Sol's ....yeah it's Friday......I cracked open ~ THE HOPCROMANCER - AMERICAN IPA!
http://www.badweatherbrewery.com/beer-series/

Cheers!

Of course with nothing less than these guys too:  NOS/Platinum/Mullard Cryogenic E188CC/7308's in my A12 an B12 Input positions~NOS/Platinum/Telefunken 6922/E88CC for Inverter Tubes~NOS RCA 0A3's.  8-)

Quote:


Why is that exactly?  Is it just an experience curve or something with the materials?  I see tubes that are supposed to be exact copies of the originals.

Steve's Russian tubes are also NOS, aren't they?

I took Steve's comment to be generally across all tubes.  That's why it caught my eye.  But maybe he didn't mean it that way.

The Russian military 6N5Ps that Steve uses (I think) and the Russian Military 6N1Ps I've been getting are all NOS.  They have a date code printed on them.  For example, they might read III/72, which I interpret as March 1972.

I bought some of this seller's tubes.  In this listing you can see the dates in the picture.  I don't know if all Russian 6N5Ps are the same or not.  In my previous post I said the 6N5Ps were "military."  Now I'm not sure.  I know there is a big difference in price between the Russian 6N1P and the military version.

Quote:

Cool about those 6N5Ps. Mine are not the same, no ink at all on them. They sound pretty darned good.

Jeff, I might take you up on your offer.  These tubes I got have a huge bias window though.  It's always hard to know what's what with a single data point.

I don't hear much difference with tube swaps, in general, in my system.  It's likely just me and how I hear, or don't hear. I kind of get an overall sense of things with time but I can rarely narrow it down to one tube, wire or whatever.  Also, a couple days ago I swapped out my ZP3 and CSP3 rectifiers and put in NOS RCA Type 80s and I pulled all the 6N5Ps from my CSP3 and ZMA and put in Russian 6N1P-EVs.  I also moved my ZR2 to be in front of my recently Anniversary modified CSP3 and then put in the KT88S.  And, to top it off, I was using a different cart than usual.  So, nothing like changing everything to make it impossible to hear what's doing what.

Thanks Jeff, much appreciated offer. However, I just went ahead and ordered a cryo matched quad from Ron S (the Lion's). I so look forward to getting these guys in my ZMA! I bet they lay the KT66's to rest... .

Could not agree more guys, the 6P's midrange is stellar and I absolutely love these tubes. The ZMA however, is about being able to run the KT88 (especially the Lion's/never to be confused with a Lion KT66-I've been told; these KT88's are special). Treble extension & sparkle up top.....overall big picture gestalt.

The 6P's & the KT88 Gold Lion's with my preferred input tubes might be all I ever need.

PS~and to be able to Bias & Balance them/dead nuts in my ZMA. Especially these guys...KT88.

One thing I did in the beginning was to mount a super quiet computer fan on the wall behind my ZMA transformers.  I keep the fan sat a low setting and I think it keeps things several degrees cooler.  This might be a good precaution when using high biasing tubes.  Steve kind of rattled me when he mentioned melting the beeswax out of the caps!  

You bet Jeff.

I will get out an initial impression and bias setting...then let them burn in 5 hours at a time....long time till the 100 hour mark....then impressions.
....Impressions at 20, 40, 60, 80 then 100 will be appropriate.

I have to remark more on the 6P's...great midrange as we know. However, with the ZDSD, I'm able to tame their top end with -.5 Input volume and -18 Reference Level output (recording dependent).

Then, I can put in the KT66 Tung-Sol's .......use -20.....and right now -18 Ref Level.....BUT, RUN +1.5 Input Volume with MACEO PARKER - LIFE ON PLANET GROOVE.....when he rises up the scale on his Alto....it is to DIE FOR.....with the ZDSD/ZMA Combo!  The whole Disc locked in at these Settings.....for this Live Recording of mind blowing!

Can't say enough about the ZDSD settings.....for Input & Output Tubes. NO, other DAC can do this.  .....Steve, great design....  ;) ........

because without your Output Transformer's....this DAC would not shine!






Tung-Sol KT66 matched quad
Reflector 6P3S-E cryo matched quad

Pending: Gold Lion KT88 cryo matched quad


~ All NOS Platinum graded Tubes from Upscale Audio (except 6N23P's):

(Great Britain) Mullard 7308/E188CC ~  2 pair (both pair Cryogenic)
(Germany) Telefunken 6922/E88CC ~ 1 pair (painfully expensive/worth it)
(US/Great Britain) Ediswan CV2492/6922 ~ 2 pair (one pair Cryogenic)
(Hungary) Tungsram 6922/E88CC ~ 1 pair
(Hungary) Tungsram PCC88/7DJ8 ~ 1 pair

(Russia) 6N23P's ~ 2 pair/came with ZMA.  





Listening Room:



Room Treatments from Michael Green & my Home Brew


Sony as Transport (DVP-NS57P)
Illuminati D-60 Digital Coax IC ~.5 meter


Shunyata Research Zitron Alpha Digital Power Cord to ZDSD {Significant}


Decware ZDSD DAC / Recorder
***************************************************************
W/Steve's Output Transformer's/kicking to the Curb quite a few superb DAC'S
***************************************************************
(@ -20 Ref Level, 0.0 Input volume and @ 16/192)
~Adjustments made often to Input volume: -.5, -1.0, -1.5 & -2.0
~Adjustments made often to Ref Level: -20, -18, -16 & -14
~+.5, +1.0 or +1.5 Input Volume...W/-20 or -18 Ref Level


WBT-0102Ag RCA Kimber Select KS1030 ~.75 meter


Decware Zen Mystery Amplifier
~BIASED at *56* mA~
NOS/Platinum/Mullard E188CC/7308's in my A12 an B12 Input positions Cryogenic~NOS/Platinum/Telefunken 6922/E88CC for Inverter Tubes~NOS RCA 0A3's & matched Quad/Tung-Sol KT66's or 6P3S-E's




***************************************************
Kimber Select KS6063 Speaker Cable 8ft WBT-0681-Ag Spades
***************************************************
Kimber (new jacket) 8TC ~ to remind me~how good the KS6063 are


Acoustic Zen Adagio - Black Pearl (Modified)
.....enjoying from 8 ohm ZMA Taps


Caintuck Audio Eminence Alpha 15" OB BASS Unit
at 43Hz, with my Velodyne CHT 130 watt plate amp and 0 degree phase
Plate Amp....regen'd clean ~ plugged into P3
Auralex Subdude (a must)
(NOTE ~ Only needed when the recording calls for...Open Baffle Bass has been the best integration I have witnessed when needed and called on)







Acoustic Zen Adagio's x-over's Modified/Full Range with Mundorf MCap Supremes-single Cap to each Tweeter/4.5k cross
(Gutted: 3kHz/18dB/Octave, Linkwitz/Riley Crossovers....with all crappy parts = gone)


ZMA, updated with robust Western Electric Bias/Balance Meter's and new Resistor's ~ Feb/17

XLO Pro Power Cord to ZMA
Shunyata Research Zitron Alpha Digital Power Cord to ZDSD {Significant}
PS Audio P3 Power Plant / Pangea AC-9SE from wall to P3
(Transport and ZDSD, Regenerated/*120*~ Multiwave off...ZMA on High Current Output)
System configured on Floor ~ Townshend Audio CD Seismic Sink deployed & other Isolation devices.

Its tailoring for Redbook is Special.

Guess what just arrived!!  My Gold Lion KT88's!  

RatsSSS!  I have to make dinner and take care of some other stuff. But, I'm a fortunate Camper!  I can get them in tomorrow morning for a run!

....till then................ .

Stone, glad you are liking them.  Who knows what's up with these "JJ" tubes I bought?  I'm not sure I'll go further with KT88s or not.  I'm very happy with what I'm getting out of my set up and 6Ps and I'm still not comfortable with the extra heat.  I'll be curious to see what you think on that too.

Worth reiterating:

You know what the really great part is? We get to run/KT88's in an Class A to AB1 Zen Mystery Amplifier!!  NOT, in some boat anchor/negative feedback Amp.  

+

....Running single cap Speaker's. Whether you're in the 95+db @ 1 watt/1 meter camp. OR, the 90 to 93db @ 1 watt/1 meter camp single cap Speaker's (like me/ZMA...my modified Adagio's Tweeter's & Woofer's are remarkable)...

....makes getting to run/HEAR these KT88's, all the more special!!


Tube compliment:
NOS/Platinum/Mullard E188CC/7308's in my A12 an B12 Input positions Cryogenic~NOS/Platinum/Telefunken 6922/E88CC for Inverter Tubes~NOS RCA 0A3's & matched Quad Cryogenic Gold Lion KT88's.

.....after my initial GAga  :o  impressions....will see if they stand the test of time...as my above tube compliment has with KT66, 6P outputs & Ediswan inputs too. The Telefunken inverter....takes things to an whole other level. ....nough said.

Stone, your GL KT88’s are biasing exactly as mine are - 80ma at start up but settle down to 78ma.  Put one in the win column for consistency of these cryo’d GL’s from Ron.  

As far as how I run mine, I don’t limit the time.  I have the Jupiter flat stacked copper capacitors.  My ZMA is well ventilated - passively.  My environmental temperature is never above 75 degrees.  It is a room that spills into two other large areas, so lots of air exchanges in my non-dedicated listening room.  I am not generally running the amp at concert levels.  All of these factors lead me to not limit my listening time.  If any one of these conditions was different, I would then re-assess and likely limit to 4-5 hours.  

Capacitors are an easily replaced part. I am ok with that.  I think I have demonstrated my willingness to do so.  I would rather maximize the enjoyment of my amp, both in sound quality and runtime, then not.  If that means I reduce the life of those Jupiters by 30%, then so be it.  I will eventually replace them with the Type II Copper & Foil anyway, since capacitors aren’t forever.  I am about living in the moment and I can’t take my ZMA with me when I die, so you bet I will be exploiting every opportunity for this amp to put a bigger smile than normal on my face.  

This is my opinion and applies to my amplifier.  Others will not be comfortable with such.  I am not sure what the internal case temperature is when running KT88’s but I have been keeping tabs on the top plate temperature quite frequently, and even after 5+ hours of use, the top plate does not exceed 130 degrees.  This is a product of great engineering on Steve’s part.  I am not sure the capacitors in my ZMA (in my environment) ever reach a high enough temperature to raise concern.  They have a maximum operating temperature of 70+ C (158+ F).  That being said, I may very well be under this value based on the plate temperature readings I have taken.  

As far as the power transformers, you have nothing to worry about.  

All this being said, I don’t advocate a reckless attitude toward operating your ZMA, but I don’t feel my approach here constitutes such.  

My doorbell literally just rang.  Guess what?  My Phillips ECG 7027A’s just arrived from the UK.  

Thanks Jeff, great peace of mind. My Listening habits mirror what you described. I will not be worrying about a nine hour on to off day with the KT88's. The 6P's will see their share of rotatation too. I agree, if the Jup's need to be replaced? Type II copper foil Jup's will go in.

Let us know about those awesome NOS 7027A's.

I'm almost an hour in this morning of the GL KT88's 6th hour of play. I'm a fan and no doubt have found my 3rd quad of output tube rotation! Being: KT88's, 6P's & KT66. I will get to my different input tubes some hours down the road, after quite a few hours on these KT88's. They are not coming out anytime soon.

Glad to read about your 7027A's Jeff. Look forward to your impressions 20, 30 hours & etc...as do I, with the cryo GL KT88's. I might try new production of these guys....but, they probably will fall short.

By the way, rock solid 80mA again this morning and settled to 78. As you said (and I only have 6 hours going on 7 with them): "Bass, and treble extension with the KT88’s is in a league of their own.  It's not just slam either.  The highs sparkle and create a wonderful balance that compliments the mids and bass."
I'm calling it: "the Powerful bigger picture of ease, Quad, with the ZMA."
Talk about maximizing Steve's great winding/ZMA output transformer's!

My Music without the ZMA, would not be Music! My second Rig is tolerable mid-fi  ;D at best.

Once again, I have no worries about the ZMA with these KT88's for 6, 7 or 9 hour sessions. When, Steve is ready this Fall or if it is next May/Spring.....I'm driving my ZMA (6.75 hours), by appointment (over night Hotel stay/Listening session too) for the mod and lets take a look at the caps then..... . I bet 20, they will be just fine.
OR, the Jupiter Copper Foils will have to go in with a complete checkup with the mod.  8-)

Have a great weekend. Happy Listening!

Damn! I'm getting scary good at voicing this Amplifier with the correct tube combo/compliments!

NOS Plat Tungsram 7DJ8's inputs ~ NOS Plat Telefunken 6922's inverter's & the cryo GL KT88's
RCA NOS 0A3's

.....just snapped the Kaleidoscope in to focus.

......Oh boy, these Gold Lion's can kick some serious ass, when you want to go there!!  Look forward to them fully seasoning in.  Wow.
My Listening "in the pocket" is a moderate SPL, for full appreciation. However, when you want to go there .....oh yeah, the LION's gonna go there....champ!

Yes! Fun factor and the ZMA grew a fuller pair with these GL's! I am running them directly (no Line Stage), getting an unadulterated sense of them.

Now:
This coming week I'll get my Audio Research Classic LS-2B MkII driving the ZMA and these puppies.

Oh, these Gold Lion Cryogenic KT88's should be outlawed!

Damn, funkin' to Stanley Clarke ~ WE SUPPLY all your funky needs!

My 15" Caintuck Open Baffle, should be criminal too. I have it so well dialed in!  

....I might get some work done later........ .

Archie, to your question. If you're not hearing the differences. Hey, stick with what quad you enjoy/grabs you.

Me? I hear the landscape difference the GL KT88's provide vs. the 6P's portrait to die for midrange. The KT66 Tung-Sol are their own animal too with my Mullard's.

The variations my input tube variety provides are certainly key.

Rock solid constant? My Telefunken's I use for inverter's. Glad I got these at 40% less than they cost now.

Roger that Archie.

Their are two more input pairs & two output quads, I do want to try/get.

Enjoy the Music! NO, further Gear either. I had quite a few pieces in here: 2012, 13, 14, 15, 16 and 17. Now, settled into my Listening Room System.  

Have a great late Spring and Summer full of great Musical enjoyment with your ZMA!

Thanks for the input on these Jeff. I might not be willing to go for the NOS/$360 on them. However, I'm considering the Tung-Sol reissues:
http://www.thetubestore.com/Tubes/7027-Tube-Types/tung-sol-7027a
why not ~ see what rolling on them will do............ .

I love this Amp. The KT88's (55+ hours now) love the killer neutrality of the Telefunken 6922/E88CC's, as do the KT66's. However, with the 6P's the Tele's are a bit much for them in the inverter slots. So, I put in the 6N23P's as splitters.....and total lock step happens with the Mullard's/input ~ 6N23P's and 6P's/output!
...........Sounds like my freaking SE84CS with POWER.

The Mull's, 6N23P's ...should bode well for the 7027A's.

Never a dull moment rolling with the ZMA!

stone_of_tone wrote on 05/17/18 at 20:09:51:


Yes, and I think my perception of its best-in-class realism has to do with the SPEED.  Speed of the 7027A tube itself and speed of my ZMA² with super caps.  

Looks funky to me Archie. I'm going to get a quad of reissue T-Sol 7027A's. I have been pleased with T-Sol KT66's, Reflector 6P's & now my Gold Lion Cryo KT88's with my NOS 6922 variants. Hope I get to go 4 for 4 with the 7027 tubes.

Arch, are you considering the ZMA enhancement (if Steve does it)? I'm enjoying my KT88's with Mullard input's & Telefunken inverter's right now and asking myself; I love the cadence of this Amp with and without my ARC Line Stage. I'm afraid if I do it? I might not like it?! I can buy the remainder of my NOS 6922 tube variants from Brent J & Kevin D for ah, 2K!

I know Jeff is quite pleased with what he did.

I know I have shown much enthusiasm for it. But, after having an out of body experience with 6P's & KT88's last night and today...I'm good.  

Will see how it shakes down I suppose, over the next year. Right now though, I don't plan on doing it.

I can't complain: I had a check-up done February 2017 (3 year check-up), with new resistor's & new backlit Western Electric Bias/Balance meter's installed.

I was thinking the same thing Archie.

I sold my: DM947 Monolith's, Zen Styx, Torii MkIII, SuperZen CKC, SE84CS & CSP3. I ain't lookin' back  :)

ZMA only.
(ZDSD, Kimber KS1030 x 2, KS6063, NOS Platinum 6922 variants, Shunyata digital cord, ARC Line Stage, P3 & A Z Adagio's/mod).    

Ah, talking about the enhancement here for the ZMA?

If you want to discuss that....cool. Otherwise, you sound odd with your comment placement in this Thread.

No big deal.

Me, and I'm sure other's/appreciate you taking the reigns and helping Steve/Decware, with the Facebook initiative. Plus, your passion for music and our Decware is second to none. I do follow "What's spinning?"....enjoy learning new music from you and others.

Sorry, to read your wife has been ill. Hoping she gets better soon Lon.

Yeah, I know, I say I'm not looking back.  

Ha! Whom am I kidding. To satisfy my curiosities thirst, I will by appointment go to Peoria for a visit. I've been a couple times and had a great time.

Whether it is late summer, late fall or even this winter or next Spring. I am only 442 miles away/door to door.

The Mono UFO3/25th's vs. ZMA enhanced (when Steve has it done and seasoned in to his liking). The gap might be really narrowed with an ZMA bypass enhancement; as he eluded to in the 25th Anni Thread (stock ZMA vs. Mono 25th's). However, hearing for myself will do it.

....I might be leaving my ZMA with him to enhance and ship back. Or, am I putting in an order for the Mono's and my ZMA will need to wait?!

Pack and carry:

(Modified) Acoustic Zen Adagio's
ZMA (in Pelican case~leaving Amp with Steve if I'm doing the enhancement/ship back)
KS6063 Speaker Cable
KS1030 IC
Sony transport
Illuminati D-60
Shunyata digital p-cord for his ZDSD on tap
XLO p-cord I use to ZMA
My favorite full tube compliment(s).

Definitely need to hear the new DNA Speaker's too.

So, to say again, the only way to satisfy my curiosities thirst, is to go into the belly of the beast and LISTEN with all well seasoned in Gear and at my 16/192 via/CD's of my collection. Will need to hear some hi-res too though.  8-)

BonnyA,
If you want to take my Gold Lion KT88’s for a spin, and are willing to cover shipping both ways, I’ve got an idle set available for a test drive.  These are the output kings in terms of power!  With you lesser efficient speakers, these could be the answer to your prayers, if you haven’t already tried them.  

Let me know if interested.

Cheers,
Jeff

I'm bumping an old thread that fizzled out in 2018...but i think the numbers in it are still good today.  I recently picked up a 25th anniv mod ZMA. Very happy with it listening to KT66s.  But I read good things here about KT88s and the KT88 is my favorite tube in my SE34I.5.  

But I don't want to run the bias at 78.  I agree that caps are replacable.  But heat degrades all electrical components. And I leave my amp on all day long most weekend days.  

So I'm interested in the mod to make the amp bias KT88s at lower numbers.  I assume it is just a resistor in series with the bias pot but I'd like to know if someone has performed it.

thanks,
Jerry