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24.27.41.140
In Reply to: RE: HK Citation V posted by Jim McShane on April 29, 2021 at 14:56:35
So by "noise," we mean hum, is that correct? I wouldn't have thought that would be an issue in a line-level stage. OTOH, it's a high gain pentode, and the amp has a spec of -85 dB. I can see how that might be a difficult number to meet.
This all relates directly to my current project. Thanks for everyone's comments!
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Buy Chinese. Bury freedom.
Follow Ups:
I believe it's the thermal noise (tube rush) that is reduced at lower heater voltages.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Well, that's completely different. Maybe I should plan to reduce filament voltage on the EF86 like Akai did. Don't want to waste time creating a DC source if that's not the problem. Do you know of any references online that might help to nail this down?
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Buy Chinese. Bury freedom.
I find some anecdotal stuff but that's all.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
on the scott 4310 one of the tubes had a lower filament voltage for noise reason.
someone I used to know called Daniel Von Recklinghausen (HH Scott chief engineer)about twenty years ago, (I think he passed away in 2010), and when subject was brought up DVR told him the noise reduction really comes into play when using lowered filament voltage in conjunction with a certain anode current for given tube.
or something like that.
Thanks, good info, I didn't realize this was a common technique. My current project is slated to use an EF86 in the front end of each channel. I was already thinking I might want to use DC on those due to some things I've heard regarding heater-cathode leakage on the newer varieties. The power transformer has an unused filament winding, so I'll just rectify that with a few Schottkys to be sure the tubes are quiet.
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Buy Chinese. Bury freedom.
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