Many questions here, searching other guitar and tube amp sites on the interweb, and I pulled the trigger and bought myself an osciilloscope! with my advanced years, I think the initial slope of the learning curve may be very steep. I did the calibration steps then hooked it up to the most recent build, an AB763 type. I am getting a bad sounding distortion past 1/2 way up on the volume control. I inserted a sine wave (1000hz) and began probing grids. Before and after the tone stack it looks fine for the whole sweep of the volume knob but at the grid after the reverb send/recovery I get this ... this capture is with the volume cranked...it starts loosing its nice pretty sine wave shape at 1/2 way up, just like the nasty distortion I’m hearing.