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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

Showing 1 response by atmasphere

atmasphere's avatar
atmasphere
7,068 posts
 
If your KT-88 amp is only making about 35 watts, it could be because the power tubes are wired in Triode mode. This is done by tying the screen to the plate. Output power is reduced but so is distortion as the tube is a lot more linear in triode mode.

If the amp is class A and triode the output power might only be 25-30 watts.

60 watts is pretty common for a pair of KT88s operating class AB1. But its possible to get more power without going into AB2 operation although I would suspect that the VAC design with 450 watts is a class AB2 design.
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