Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Lambertini on March 14, 2024, 02:43:19 pm
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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 (https://soundcloud.com/ekovah/weird-noises)
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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
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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...
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Yeah, I found mine on a scope. Still never solved it though.
Dave
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Yeah, I found mine on a scope.
Where did you locate the source?
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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
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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.