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ZMA tube bias below 50? (Read 2311 times)
Archie
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Re: ZMA tube bias below 50?
Reply #50 - 05/03/18 at 15:47:02
 
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.
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stone_of_tone
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Re: ZMA tube bias below 50?
Reply #51 - 05/03/18 at 15:59:21
 
I completely understand Archie. The 6P's are incredible tubes. I will not be without them. Your's (KT88's) are biasing funky...so I can further see your concern.

I'm going to stick to the rules of the ZMA, that the Zen Master laid down. Respect, getting to run them in Class A and shut her down after a 5 hour (max) Listening session with these guys. The trannies can take the temp as we read previously...however, we need to respect the heat on the caps!

....the 6P's ....and KT66....you can run all day.

Oh boy, Ron must have burned these in for 48 hours. I don't want to shut them down....the majesty/warmth & detail, of the midrange is coming through....the POWER....and weight.......... . Now, 2+ hours and fully warmed up.....they are worth every penny. They will only get better too, as we know..... .
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Re: ZMA tube bias below 50?
Reply #52 - 05/03/18 at 16:38:14
 
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.
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Re: ZMA tube bias below 50?
Reply #53 - 05/03/18 at 17:08:12
 
Jeff, do you limit your time at 4 to 6 or 7 hour Listening sessions with your KT88's/78mA? ....because of concern for the inside and secondly the power trannies?

....distant second/concerning the Hammond power tranformer's (221F)...and we're well under that temp. ...and I understand Archie, you're not comfortable with the Tranny heat..... . I'm okay with it.

.....concern for the caps on the inside is my main concern as Steve mentioned. Whether the former or the latter Jupiter's as Steve mentioned as well. Plus, for you Jeff, Mundorf's now under the hood.

...I want to have her on more than 5 hours......... .
Heck Jeff, if you have been comfortable about going 8 or 9 hours continuos with KT88's in? I did go 5 hours today with lock solid 78mA. Power trannies heat as I knew was coming and I'm fine with it. The chassis seemed to be dissipating well. Well enough for a 9 hour run is the question, time and time again?
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Jeff of Arabica
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Re: ZMA tube bias below 50?
Reply #54 - 05/04/18 at 00:26:10
 
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.   Smiley
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Archie
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Re: ZMA tube bias below 50?
Reply #55 - 05/04/18 at 00:58:20
 
I didn't realize the caps could take so much heat.  I think of beeswax as generally melting lower but I don't know its melting point either.  I typically don't listed for even 4 hours straight but sometimes I leave my amps on all day.  If I could train myself not to do that I'm sure I'd be fine.  I think my fan keeps the transformer temps as much as 10 degrees cooler.  I've never measured the plate temp but I think it's less than the transformers and might be heating due to tube radiation more than from the transformers anyway.
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stone_of_tone
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Re: ZMA tube bias below 50?
Reply #56 - 05/04/18 at 01:19:11
 
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.
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Jeff of Arabica
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Re: ZMA tube bias below 50?
Reply #57 - 05/04/18 at 06:57:59
 
The Philips 7027A's, like the 6P's, are rock solid on their bias stability.  The bias range spans about 44ma to 79ma.  Right now, I have them biased at about 68ma.  Heat measured at several areas on the amp is slightly less than the KT88's at 78ma, but not dramatically so.  I did find myself having to make micro adjustment to keep the bias balanced with the GL KT88's.  So far, these have settled, and stayed put, similarly to the 6P's as I mentioned.  

I am impressed with Watson Valve's matching and burn-in process.  It appears I am witnessing the byproduct of their diligence.  

I have enjoyed them very much so far - 4 hours in.  They are definitely different than the KT88's.
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Re: ZMA tube bias below 50?
Reply #58 - 05/04/18 at 13:37:30
 
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!
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stone_of_tone
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Re: ZMA tube bias below 50?
Reply #59 - 05/04/18 at 14:33:44
 
I take back waiting to roll input tubes.

My Mullard's & Ediswan's are a match made in heaven with the clean neutral absolutely transcendent Telefunken's as inverter's...with the 6P's & KT66's.

However, it is apparent I should take a 180 degree turn (and why I own them), put either my Tungsram 6922/E88CC or Tungsram PCC88/7DJ8 in for inputs.

The already smooth warm infectious KT88's should love these!  

I will put the Tung's in (7DJ8 incredible tube)....for an extensive seasoning in of the cryo GL KT88's....then return the Mullard E188CC's.... .
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stone_of_tone
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Re: ZMA tube bias below 50?
Reply #60 - 05/04/18 at 16:48:24
 
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!

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Jeff of Arabica
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Re: ZMA tube bias below 50?
Reply #61 - 05/05/18 at 00:32:20
 
Exactly Stone!  They are something special in this amp.  They are the ballsy-est tubes I have every placed in my ZMA.  The fun factor is off the charts.  Glad they fell right into place and you are getting right to some complimentary tube rolling to get this most of them.  They just ooze goodness.  

I am loving these Philips ECG 7027A's.  Different from the KT88's for sure.  Great in their own right, based on my limited listening.  Running through my usual reference tracks during burn-in.  

Happy Friday!

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stone_of_tone
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Re: ZMA tube bias below 50?
Reply #62 - 05/06/18 at 17:27:54
 
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.
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Archie
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Re: ZMA tube bias below 50?
Reply #63 - 05/07/18 at 01:24:12
 
Quote:
They are the ballsy-est tubes I have every placed in my ZMA.  


I know Steve is fond of this expression too.  Can someone define "balls" for me as it applies to amplifiers?  Preferably, without using other nondescript jargon terms.  I'm serious.  I have a lot of trouble understanding what to listen for when making tube changes and having some better definitions of the terms used might help?   Undecided
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Re: ZMA tube bias below 50?
Reply #64 - 05/15/18 at 17:46:58
 
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........ . Grin
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Re: ZMA tube bias below 50?
Reply #65 - 05/15/18 at 19:17:22
 
Jeff, how are you making out with those NOS 7027A's?

How do they compare to the 6P's of similar envelope?

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Re: ZMA tube bias below 50?
Reply #66 - 05/15/18 at 22:23:23
 
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.
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Archie
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Re: ZMA tube bias below 50?
Reply #67 - 05/16/18 at 00:39:39
 
Stone, this forum can drive a guy crazy.  While I'm very happy with what I'm hearing, there are so many temptations to try!
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Re: ZMA tube bias below 50?
Reply #68 - 05/16/18 at 15:04:26
 
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!
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Jeff of Arabica
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Re: ZMA tube bias below 50?
Reply #69 - 05/16/18 at 17:04:36
 
Stone,
The 7027A's are similar in several ways to the 6P's.  I have them biased at 68ma right now.  They can go higher but I am trying to get a feel of them here before cranking them up.  They are pricey suckers so if there is little difference at the higher bias, I will run them as low as I can without any noticeable drop-off in sound, because I want them to last.  

They look similar in construction since they share a lot of design features to the 6L6's (American version of 6P's).  They even have that blue glow!  

However, I am getting better/stronger output with increased dynamics over the 6P's.  They are have a slight edge in the "excitement" department, but not quite in the realm of the GL KT88's.  

I would say the mids are as dreamy as the 6P's, so that is a win!  If I was to put my finger on its greatest strength, other than the gorgeous mids, it would be their ability to present fine details at all volume levels.  I am also getting a bit better soundstaging, which together with the improved resolving of detail creates an authenticity to the sound on my ZMA that is pretty amazing.  These tubes could be the best I've had in my system from a realism perspective.  

Are they better than the 6P's?  I am comfortable saying, yes.  But I don't believe the difference will smack you upside your head or bowl you over necessarily.  Yes, it is definitely audible if your system is up to snuff, which yours certainly is, but they are $360 a matched quad - a tough pill to swallow.  If they were half that price, it would be an absolute no brainer. But if you are at the point where you want to leach out every advantage/improvement humanly possible, this investment may make sense.  But that is subjective and there are some things I prefer in the KT88 line of tubes.  

I am still burning them in and getting to know them so I may have additional to report in a hundred more hours or so of critical listening.
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Re: ZMA tube bias below 50?
Reply #70 - 05/17/18 at 18:56:58
 
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!
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Re: ZMA tube bias below 50?
Reply #71 - 05/17/18 at 20:09:51
 
Yes, to your point of: "I will run them as low as I can without any noticeable drop-off in sound, because I want them to last."

I roger that.

Interesting/the bias points:
my 6p's @ 48mA
my KT66's at 58mA
my soon to be 7027A's (reissues) @ potentially 68mA
my KT88's at 78mA.

I like what Steve said about the NOS. Will I have the same result with Tung-Sol reissue?!   I will need to find out........ .

"Jeff,

I believe based on all the tubes I've heard in my lifetime that there is no faster 8 pin output tube than the 7027's and also the most neutral.  It's total hardcore.  In a push-pull amplifier there is absolutely nothing that has the leading edge attack and slam to back it up of a 7027.

Steve"

you wrote: " I am getting better/stronger output with increased dynamics over the 6P's."
+ " These tubes could be the best I've had in my system from a realism perspective."

....more hours on them as you mentioned too, are needed. I will get my reissues some time in July.....to damn busy the next 6 weeks.
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Re: ZMA tube bias below 50?
Reply #72 - 05/17/18 at 21:20:00
 
stone_of_tone wrote on 05/17/18 at 20:09:51:
+ " These tubes could be the best I've had in my system from a realism perspective."


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.  
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Re: ZMA tube bias below 50?
Reply #73 - 05/19/18 at 18:40:59
 
Quote:
4 x 7027A RCA Tubes

Made in USA

O Getters

Tested on Enhanced Triplet E3444 Laboratory Tester

6180 micromhos @ 69 mA
6200 micromhos @ 90 mA
5820 micromhos @ 67 mA
6415 micromhos @ 82 mA

Industry Bogey(100%) = 6000 micromhos @ 72mA


Are these really matched tubes?  It seems that if biased all the same then the micro ohms would be off.  I don't really understand what's going on here.  The seller claims they are matched to 10% based on the micro ohm readings.  I'm thinking he's dreaming.   Undecided
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Re: ZMA tube bias below 50?
Reply #74 - Yesterday at 15:08:50
 
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.
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Re: ZMA tube bias below 50?
Reply #75 - Yesterday at 15:31:17
 
I'll see what Steve comes up with.  My first thought is that I would do it.  It would also be a good opportunity for a full ZMA check up.
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Re: ZMA tube bias below 50?
Reply #76 - Yesterday at 15:52:15
 
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.
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Re: ZMA tube bias below 50?
Reply #77 - Yesterday at 15:58:05
 
Seeing the price of the 25 Anniversary amp, I can't see getting two to replace my one ZMA!   Cheesy  The ZMA mod might be a deal for those of us with one.
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Re: ZMA tube bias below 50?
Reply #78 - Yesterday at 16:56:09
 
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).     Wink
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Re: ZMA tube bias below 50?
Reply #79 - Yesterday at 17:10:37
 
I'm not looking back either, but what I'm not looking back to is the EL34 type tubes and push-pull. The UFO transformers and the 25th Anniversary tech have made me no longer long for those and I don't need the power that those amps deliver. The 25th Anniversary SE84UFO3 are stunning me when I can listen to them. And the Taboo Mk IV is fantastic for headphones, which I've had to really on all this month as my wife has been ill. I'm probably even going to sell my trusty old Torii Mk III and keep the Mk II as my amp to drive the Traps upstairs. . . .
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Re: ZMA tube bias below 50?
Reply #80 - Yesterday at 17:32:20
 
Roll Eyes

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.
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Re: ZMA tube bias below 50?
Reply #81 - Yesterday at 18:08:10
 
I see this whole board as one conversation. Just  saw you're "I won't go back" comment and it made me realize I won't either, it's just in a different direction. Sorry if this bothers anyone.
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Re: ZMA tube bias below 50?
Reply #82 - Yesterday at 18:16:00
 
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.
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Re: ZMA tube bias below 50?
Reply #83 - Yesterday at 18:19:44
 
Thanks. She IS getting better, and I'm hoping she'll be back at work soon. . . for our financial health and my mental health (in that I really need a few days fully immersed in my system!)

I hope you ZMA-ers can get a taste of the 25th Anniversary tech soon enough. It's a real step forward in Decware sound. And it surprises me how firmly the Monoblocks and the Taboo Mk IV moved me into the "small quick tube" camp.
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