NewYorkDave wrote:

Patrick Turner wrote in message ...
Your first post on the matter seemed to present a daunting task for us to
design for you

Patrick, I think you misunderstand my intention in the original post.
I'm not asking anyone to design my circuit for me. I just wanted
comments on the distribution of distortion products in tube amplifiers
with negative feedback. This knowledge could help to guide me in
designing my circuit, but I wasn't looking for someone else to do the
design work for me.

I think the important fact to keep in mind is that negative feedback
does not have much chance of increasing the high harmonics when it is
used to suppress the low harmonics, It just allows them to be more
audible, because the low (and more pleasant sounding) harmonics get
reduced more than the higher (less pleasant) ones do. This is a
result of there being more excess gain and less phase shift at the
lower harmonic frequencies.

So, first, you try to design an amplifier that has lowest amount of
the higher harmonics before the loop is closed. The feedback will
then take care of the lower harmonics, as long as you stay well away
from saturation, where the open loop gain falls to the point that the
negative feedback drops out right when the harmonic content jumps up.
Headroom is probably more important than harmonic purity.

None of this is scientific, but just rule of thumb stuff.

--
John Popelish