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How do tube manufacturers like VAC get 55 watts per KT88 where others get only 30-35?

Just wondering how some push pull tube manufacturers like VAC and others get 55 watts per KT88 tube while others are more in the range of 35? Does driving a tube hard like this have any ramifications as to distortion, sound, headroom and tube life? I know VAC amps are highly musical so design, power supply and output transformers obviously contribute much to overall sonics. A company like Zesto gets about 25 watts per KT88 but uses a class A push pull circuit rather than class AB.  This seems like an attractive design.
I guess, as always, it's all in the implementation. Thank you for helping me to better understand.

normie57
tbanis
12 posts
 
Hi all !
Class A, AB etc. But I also noticed that there are output transformerless KT88 systems. I believe its a so called cathodefollower?.
Then again comparisons with SS amps is difficult.... Tube amps are voltage related instead of SS which are current related.
Another thing.... output transformers have a specific habit. So quality of these is realy important and will take a prominent place in the pricetag..
But most important: the fun you get from your equipment!
regards
Ton
normie57 OP
50 posts
 
I would still love to know how VAC gets 100 watts per pair of KT88s without tube reliability issues or distortion. Probably some proprietary secrets, the intelligent auto bias,  as well as huge power supplies to comfortably generate the needed plate voltages.  I have heard Kevin use The Signature 200 IQ in monoblock configuration at a couple of shows and the sound was memorable.  I'll place an order and give them a spin in stereo first.  I would also love to hear from Zesto amplifier owners, either the Bia 120 or Eros 300.  Thanks so much!
bdp24's avatar
bdp24
9,738 posts
 
I don’t know about Kevin Hayes and his VAC designs, but Roger Modjeski details how he gets 100 watts out of a pair of KT88’s in his Music Reference RM-200 in the company’s now-dormant AudioCircle Forum. I know MR isn’t as hip and cool as VAC, but what Modjeski has to say may still be found to be of some interest and/or value.
djfst
169 posts
 
normie57,

Didn't know if you were still interested in the VAC 200 IQ, but one just one up on audiomart at a great deal.  Any updates?  Keep us posted.
ebm
9,311 posts
 
Wow this is very important will be up all night thinking about that one.
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