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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
mechans
3,048 posts
 

My Jadis DA-60 gets only 60 watts out of 4 KT -88s per side, in case your counting that's 15 per tube.  In  class A, push parallel  pull pairs, if I recall correctly. They could be understating the true output in addition you can use different output tubes in this amp.

I think the output transformers playing role in shaping the sound of most tube amps.

bdp24's avatar
bdp24
10,008 posts
 

Definitely mechans. Modjeski offers ot that he hand winds himself as a thousand dollar option in the RM-200T, but the standard ones in the non-T version of the RM-200 Mk.2 are real good, custom built for him to his specs.

Dang Normie, that's a lotta tube power! Just think---Kevin Hayes makes 450 watts with 8 tubes, yet the Atma-Sphere M-60 also uses 8 tubes to create only 60 watts. But then it doesn't have output transformers, which is even better than really good ones!

mid40sguy's avatar
mid40sguy
163 posts
 
Kevin Hayes of VAC has stated in part it's due to the output transformer design. Lovely sound that's a fact.

jond's avatar
jond
5,926 posts
 
Topology and Class have a lot to do with it as well, Pentode vs Triode and Class A vs Class AB. A case in point my own amp uses a pair of El34’s per side and puts out 17 wpc, you see other El34 amps with the same output  tube complement putting out anywhere from 25-40 wpc. My amp is triode wired and Class A, and runs the tubes conservatively. Pentode and Class AB with both give you more wpc, albeit with different sound characteristics.
georgehifi's avatar
georgehifi
10,312 posts
 
Many ways of using this tube, Tetrode Ultralinear,Pentode, Triode in push/pull mode, all with different wattage results.

Cheers George
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