[Don[_4_]]

If I had two KT88's (I wish!) I'd build the Williamson design, but
stabilize it with the "low frequency shelf" discussed here at length a
short while ago.
Cheers,
Roger

Regarding the "low frequency shelf" and high frequency
roll-off filters:
why are they usually after the voltage amp?
Why not a band-pass filter before the V1 tube?

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-Don