Funny that you mention altering the tone controls. Just last night I happened to find a review of this amp online and the user said to achieve a decent clean sound the bass control should be set at 10, the treble set at 0, and adjust the mid around halfway. So I guess changing the values of the eq controls might be the way to go in this case. I can always experiment with different coupling capacitors while I'm in there. Where would I find the tonestack calculator? Yes, the schematic is very hard to read in some parts, unfortunately this was the only one I was able to find online.