I posted one video on Tube Squeal that focused on the 2nd stage preamp. This video focuses squeal and hum produced by the 1st stage. The cathode resistor is not just a way to set bias, it is the feedback circuit, therefore, grounding the feedback circuit correctly is important. I also discuss 3 basic preamp grounding configurations.
Original Work, Copyright 2022 James D. Whiteside, II all rights reserved, For consideration only, no reproduction without prior permission.