Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: LooseChange on August 18, 2012, 11:17:58 am
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I've got one of these on the bench.
The unit is noisy and has a hum that is not filter cap related or heater related.
I did some research and this guy Ken Fox suggested this... I inserted a 100 ohm resistor from the pot leg to ground (raising the off position 100 ohms above ground). Issue fixed.
I am not sure I understand what he means or how this would really work. Is he saying add this to the AC switch on the pot?
Schematic attached.
Thanks for your help!
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I think he's saying to put the 100R between the pot's O end and ground. He's lifting the pot 100R above ground.
Why that would make a differance? :dontknow:
Brad :icon_biggrin:
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What have you already done to resolve the hum?
The Premier looks like a close cousin to the Fender 6G15 reverb. You already know how seemingly small grounding issues in an otherwise fine amp can get the reverb humming.
So maybe the standard build style for the Premier has hum loops built into it. I'm guessing the guy you quoted found that by isolating one of those grounds from the rest of the circuit eliminated the noise. But it seems like there should be more to the story, probably related to physical placement and build execution.