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