I would like to add a bias mod to my Buster head, but I cannot find a schematic for the power amp. While I’m no amp tech, I can safely work on high voltage equipment. I haven’t opened up the amp itself yet, as it gets played nearly every day. As far as the bias mod, I know in theory how to add a pot for each tube, but it seems like it might be easier and as effective (since I would be using a matched set) to use 1 pot for each triplet? Or for pairs? If pairs or by trio, would you mind detailing where to insert? Do you remove the resistors, tie the grounds together, replace with a resistor/pot of 1/3 range (for a trio) - due to the current from 3 tubes? Would anyone mind helping me understand how to best approach this? Also, has anyone used the Tung-Sol 7581A tubes in these? Thank you!