Hi... So I just bought a Mesa Mark III Simul-Class head. Anyway I am looking at adding an adjustable bias. Here are the Schematics to the poweramp section: http://www.intensemetal.com/~aortizjr/projects/mesa-mkIII/mesaboogiemark3b.gif I see where the bias section is. But what mod actually needs to be done. I am guessing that I just replace the "factory selected" resistor to a pot and go from there. Except that I am having to bias both EL34's and 6L6's. So I would guess that I would have to mod it some way to have adjustable biases for both. Is this the case or should I just put the pot there and be careful with my tube selection? Or is there something completely different that I need to do with the mod? Any help at all would be great.