Thanks to all those responding. Very informative discussion, and again, I'm awed by the collective knowledge of those on this board and the time they take to share it with others.
I was unaware of the need to check caps for damping, but it certainly makes sense after reading the above comments and links. In my particular amp mod, the Black Gates are so much bigger than the stock caps that they had to be mounted standing above the PCB on longer leads.
I'll definitely study the best way to damp them so they don't sing like tuning forks. I'm guessing that's exactly what they are doing in the present set-up now that the symptoms have been described.
I was unaware of the need to check caps for damping, but it certainly makes sense after reading the above comments and links. In my particular amp mod, the Black Gates are so much bigger than the stock caps that they had to be mounted standing above the PCB on longer leads.
I'll definitely study the best way to damp them so they don't sing like tuning forks. I'm guessing that's exactly what they are doing in the present set-up now that the symptoms have been described.