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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
jond's avatar
jond
5,916 posts
 
Charles you are so right so many roads and they are all valid. I lucked into mine, acquiring my amp because it sounded good, not at the time really truly understanding what went into its design. Now that I know more I am still enthralled by the sound and appreciate my amp even more. And agreed on power supply and transformers both should be high quality and overspeced.
normie57 OP
50 posts
 
Thank you all for your input!  Agreed....many roads to Rome or great sound.
I'm considering a VAC Sig 200 IQ stereo unit using a total of 4 KT88 delivering100 Wpc in class AB1 or AB2, or a Zeso Bia 120 stereo unit, also using 4 KT88, delivering 60 class A Wpc.  Both are in the $12,500 to 14,000 range.
Your thoughts and preferences would again be appreciated.  
charles1dad's avatar
charles1dad
10,250 posts
 

I can say that both of these amps represent good examples of high quality push pull tube design. The VAC has the well earned high status allure. I've heard the less known Zesto Bia amp and thought it was exceptionally good sounding.

Charles

jond's avatar
jond
5,916 posts
 
normie what speakers are you going to be driving? I assumed your question was more theoretical but looks like you're in the market for a new amp. So the more info you can share about your system the better.
normie57 OP
50 posts
 
Thanks Charles and jond:  I will be driving KEF Ref 3 loudspeakers. My preamplifier is VAC Ren 5 and my room is very modest at 14 x 16 ft.  I'm tempted to go Zesto Bia 120, albeit less power, as class A and running tubes conservatively sounds enticing.  However I know VAC is synonymous with great sound. I owned a VAC Phi 70 a decade ago but that was a much different 300B beast.  Both the VAC Signature 200 IQ and Zesto Bia 120 have transformer coupled balanced inputs.  Thanks!


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