01-13-2018, 06:47 PM
I tore the amp apart (getting really tired of doing that) with an eye on that first gain stage. The components all tested fine. The voltages on the plate and cathode were more or less identical to the other triode of that tube. There was no DC on the pot. Basically, it came down to four components: plate and cathode resistors, and cathode bypass and plate coupling caps. I just swapped them all out, as there was nothing more that I could easily do to identify the issue. I've put the amp back together (again, getting really tired of doing that) and the noise is gone.
Slider - thanks for the input. I already was thinking about the coupling cap (but it *seemed* OK). If I put everthing back together and the noise was still there, it left only the jack and the tube socket. When I cleaned the sockets I did not retention them. I know that I should, but that is an exercise that always makes me nervous. I've destroyed at least on socket by pushing a socket connector a bit too far. I need to collect some old sockets to practice on.
Anyway, I'm done with it for today. Tomorrow I'll give it a good run. I've also invited a bass player friend over, but we'll see if he has time this weekend.
Slider - thanks for the input. I already was thinking about the coupling cap (but it *seemed* OK). If I put everthing back together and the noise was still there, it left only the jack and the tube socket. When I cleaned the sockets I did not retention them. I know that I should, but that is an exercise that always makes me nervous. I've destroyed at least on socket by pushing a socket connector a bit too far. I need to collect some old sockets to practice on.
Anyway, I'm done with it for today. Tomorrow I'll give it a good run. I've also invited a bass player friend over, but we'll see if he has time this weekend.