Hi all As part of my recent Bassman Micro build I added a little circuit to adjust the bias on the EF80 output tubes along the lines of this but with 2 pots so I can adjust each tube indipendently. https://robrobinette.com/Generic_Tube_Amp_Mods.htm#Adjustable_Balanced_Bias The idea being that EF80s weren't really designed for guitar amps and finding a matched pair would be unlikely so I could balance whatever I got. It didn't work and I removed it but on thinking about it I've realised that I may have made a very rookie error. The amp is cathode biased by design with the tubes sharing a 300R cathode resistor which I'm now thinking probably means that I can't apply this type of circuit to adjust each tube. Is it time for the pointy hat with a big D on it..