In Reply to: RE: You are absolutely right! posted by Banat on October 21, 2010 at 05:28:04:
Best performance corresponds to 6-13 dB feedback.
http://www.audioasylum.com/cgi/vt.mpl?f=tubediy&m=190082
This is my last project and I have recently added a top panel switch to select 9dB or 14 dB NFB.
Even though the amplifier is very natural with zero feedback too when using 14 dB setting the absolute performance is (believe me or not) undistinguishable from my OTL!
In my opinion high plate voltage, almost zero PS impedance and high bias current (i.e. true class A operation) allow tetrode amplifiers to match OTL triode performance.
Best Regards
Luca
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