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In the Forum: Melquiades Amplifier
In the Thread: Single-stage Melquiades vs. DHT amps
Post Subject: Hiss or HumPosted by Paul S on: 5/6/2009
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If you have nothing more than low hiss, as you describe, then you are probably about There. In my experience, at any rate, it's either some hiss or some hum, compared to true silence, like the ML2, etc.
Do not give up before you try all parts hard wired, no jumpers, wherever possible, and do try the plate and cathode resistors straight down under the tubes, like they used to do with the old tubed Sonar and other exotic listening equipment. If nothing else, that gear was pretty quiet...
I'm not saying regulation is not important, but IMO it should be kept to the minimum acceptable, while more attention than usual is paid to grounding and isolation, perhaps even down to separate filament supplies for the tubes, because of their separate/varying ground planes, if it comes to that. Whether to use copper screen or Mu metal shield is case-by-case, if you need one, and if ground stacking is otherwise done correctly.
Sounds like you're close; and remember, part of the reason you're doing this is for the drive (and harmonics...), vs. 1-stage...
Best regards,
Paul SRerurn to Romy the Cat's Site