Tweed 5E3: ghost oscillation behind notes

[Lambertini]

Hello!
Working on my new 5E3 build, I'm facing a new issue: some weird oscillations (like old modems...) appears after few minutes of heating, a while after some uggly ghost oscillations came after each bass notes.
Any idea where does that can come from?

Sound clip

[Dave]

I have read a lot about "Ghost" notes because I have encountered them to a super annoying degree on one amp. The consensus seems to be inadequate power supply filtering, but my experience with them was unsolvable. At least, unsolvable by me. Good luck.


Dave

[Lambertini]

The consensus seems to be inadequate power supply filtering, but my experience with them was unsolvable. At least, unsolvable by me. Good luck.

Thank you Dave. I don't think so, I've upgraded the 1st filter cap to 30 µF, with absolutely no effect on this. Could be a bad tube but I haven't 6V6 and 12AY7 spare yet. On their way.
I suppose I would have to track them with a scope...

[Dave]

Yeah, I found mine on a scope. Still never solved it though.


Dave

[Lambertini]

Yeah, I found mine on a scope.

Where did you locate the source?

[Dave]

Mine was a different amp, but I found it at the second gain stage plate/output. Never found any solution. If that gain stage was in play, it ghosted.


Dave

[Lambertini]

Mine seems to be generated, or at least sustained, after V1/V2 (preamp/PI). With preamp tubes installed, once the "old modem noise" starts, chanel volumes have no effect. Tests with V1 and V2 removed on-going.