I built this... Here’s the build thread... https://www.tdpri.com/threads/seems-like-i’m-doing-this-backwards.1015555/ It makes the most glorious clean sounds you can imagine. Cranked, not so much. I have been literally (in the true definition of the word) using every spare minute to read everything about the AB763 circuit and some little known issues that are commonly misdiagnosed. I’ve been sticking my scope probe into this one for a few days to come up with a game plan for fixing the bad sounding distortion without messing with the clean character at the other end of the dial. One of the biggest symptoms is this odd shaped scope shot... This is at the speaker jack with a 1k sine wave fed in. It gets nastier the farther up you turn the knob. It goes back To a normal looking wave If I pull the (1-tube) reverb tube. Before I get as deep into the circuit as the reverb, I want to address what appears to be grid clipping at the second gain stage. The first gain stage keeps a nice looking sine wave all the time. The second stage wave top gets flatter the more the volume is turned up. The top of the wave never moves...the bottom does what is expected. To me, it looks like the AB763 uses the volume pot as the stage II grid resistor. As an experiment, I grabbed a couple loose resistors and added a grid stopper and grid leak resistor in front of V1b grid as I scratched onto the schematic below... The addition of these parts makes the scope results look much better and it does make the amp’s cranked distortion sound better (departing from the realm of full on blocking distortion) but it does pull down the overall volume a bit. Is there a good/better/best combination of values for this mod?