Tube amp bias

I have tried this and my experience is that you don't really gain anything beyond
increased noise and shortening the life of the tubes. Audio amps are not guitar
amps, where such an increase in the bias can provide nice distortion. My sense
is that the manufacturer knows best what the optimal operating parameters are
for their products. Stick to the bias recommended by the manufacturer.

Stevecham is spot on. I spoke with Dennis Had before he retired and he said he likes to run the Cary CAD120's amp at 160mV (t - 10) the manual calls for 140mV (+ - 10) I run mine at 150mV and it works fine. I run 8 KT88's and 4 6sn7's. If your bias is spot on you should be happy with the results. Keep a second set of KT90's on hand. Happy listening.