Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: nensign on February 25, 2023, 03:39:36 pm
-
Hello,
My wife wanted a guitar amp built into an old radio cabinet so I tried. There was a pretty annoying buzzing noise. I ran the input, volume and power on/off out of the chassis to the front of the wooden cabinet. For the volume and input I used small coax with the shield grounded to the chassis. Of course the power was twisted. When it didn't work I modified it several times including making a shield from half inch coax for the outside wiring. Disconnecting the magic eye tube made no difference.
My question is: Is this possible to do or just a bad idea?
I made this same amp a few months ago with everything mounted in the chassis and it worked awesome!
Thanks!
-
while a cool box, the other side where the hum is would be a helpful pic, maybe a schematic also.
you still using 2-prong?
is the hum 60hz or 120hz?
is your input jack a shorting jack, with the pre-amp ground connected there and the PA section ground connected far away?
-
I removed the amp from the box so I can start again. I posted a link to the schematic under the pic.
I'm using a 3 prong plug. The hum is closer to 120hz. The input jack is not a shorting jack.
I've rooted around inside the amp way too much! Now it's making a wailing/screeching noise and sounds like it's possessed by demons. Might be time to start over.
Mostly I'm wondering if there is a good way to run the input and volume wires 6 inches or so from the chassis without creating noise.
-
Your coax shield should only be grounded on one end.
If grounded at both ends could created a noisy ground loop.
-
It was only grounded at the chassis end.
-
Is there a schematic?