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In Reply to: RE: he was... posted by mfitz on May 11, 2021 at 12:32:09:
Mike said:"Using dc on everything in the pre, copied from bartola valves. The power amp has ac on the filaments.I later added hum pots. This helps but not a cure. My speakers are about 90db. Can hear noise with no music playing. Not ear up to speaker. Going to add 12uf to second stage of power supply. This helps some. With the pre off and amp on noise is mostly hum."
Mike . . . Good to see that you've returned to the thread . . . . perhaps there will be at least some discussion related to your problem.
When you first posted about this years ago, you claimed you had eliminated the noise and that the amp was now totally quiet. Was that accurate? Or did the hum return at some point?
When you indicated that the hum in the amp had been solved but then returned after you built the preamp, that suggests that either the issue was in the preamp or possibly there was a ground loop created when they were used together.
Now you say that the "noise is mostly hum" and that it's present without the preamp. Does that mean the preamp is not connected to the amp at all, or is it connected but just not powered up?
If they're still connected, perhaps it could still be a ground loop. If they're not connected, that points to the amp. I have one question and one suggestion.
The question: Does the amp use one of those big Signal industrial control transformers (or similar) that the Reverend was promoting at one point, or does it use a more conventional power transformer?
The suggestion: use DC for the filaments
Pics would help, too.
Edits: 05/12/21 05/12/21
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- RE: he was... - FlaCharlie 06:22:17 05/12/21 (0)
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