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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: DC Filaments for EL-34s? posted by JimWayner on January 2, 2010 at 15:35:39:
Further update - after putting a scope on the amp while I was listening to get an idea of where clipping started, I found some pretty big high frequency spikes on the output. More digging around with the scope and in the forums pointed me to having a diode commutation noise problem. It was big enough to be measured in volts on the grid of the EL34s and was an overdamped spike of about 120khz at a 120hz interval. I subbed some UF4007s into the power suppy paralleled by a .001 cap in series with a 100 ohm resistor (wild guess at snubber values) and the noise just went away. No more big spikes anywhere, and the buzz that has been bugging me for ages went away. You can't tell the amp is on from more than a couple of feet from the speakers in a quiet room, and that's connected to the preamp via 10 feet of crappy RCA cables running parallel with power cords. There just isn't any significant hum coming from the filaments, this was a wild goose chase.
Jim
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Follow Ups
- RE: DC Filaments for EL-34s? - JimWayner 11/14/1013:30:32 11/14/10 (0)
- RE: DC Filaments for EL-34s? - sganti 22:06:48 11/14/10 (0)
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