Have a question for the turntable crowd, hopefully thats ok. I trust this place more than most internet communities. I recently installed a power switch on my cheap-o ART Phono Preamp. I simply cut the trace on the board between the diode bridge rectifier (it runs off a 9VAC wallwart) and the main filter cap and put a toggle switch there. The switch works great however I am getting a ground buzz/hum now even when I have the turntables dedicated ground wire connected to the ground post on the preamp. The ground post just goes to chassis and I am reading 0 ohms from post to chassis. When I touch the ground wire to the shell of the RCA jacks on the preamp it's dead silent. When I touch the ground wire to the chassis of my power amp it is also dead silent.
What am I missing here?
Just a guess, but let's see what you think of it....
You have a highish voltage with lots of ripple passing through the switch. The switch is mounted to the chassis. The circuit ground through the box is coupling capacitively with the conductive path through the switch.
Try this -
Restore the cut trace. Switch the power on the input side, ahead of the bridge, instead.
> power switch on my cheap-o ART Phono Preamp.
Why?
Let it run all the time.