Was sorting out my SRPP, where I used to get some crosstalk from other channels, and relays wouldn't select all the time. I didn't connect a ground as I thought it unnecessary -- I hooked the grounds of the RCA ins to each other and to the signal ground on the volume pot board, and the hot pins of the RCAs to selector board and then to the volume board -- didn't think the selector board also needed ground as it only switched the hot pins.
So as it turns out the ground was needed -- but what I don't understand is why I get this fierce ripple from the selector board -- when nothing is plugged into it, and it is plugged into nothing. Basically, the board is hooked up to the RCAs, which are empty, and there's no power to the board. But if I put the probe to the loose signal wire coming off the board, i get his crazy ripple.
Sure, I get it that high impedance floating connections can do weird things -- but what can it be picking up? It's a 50Hz (mains I assume) fundamental with jaggies all over - this is reduced by turning off lights, etc near it (12V halogen lamp with a txformer).
But I'm curious -- it's 100-200mV, not inconsiderable. And I get nothing like it if I touch probe anywhere else on amp.
So as it turns out the ground was needed -- but what I don't understand is why I get this fierce ripple from the selector board -- when nothing is plugged into it, and it is plugged into nothing. Basically, the board is hooked up to the RCAs, which are empty, and there's no power to the board. But if I put the probe to the loose signal wire coming off the board, i get his crazy ripple.
Sure, I get it that high impedance floating connections can do weird things -- but what can it be picking up? It's a 50Hz (mains I assume) fundamental with jaggies all over - this is reduced by turning off lights, etc near it (12V halogen lamp with a txformer).
But I'm curious -- it's 100-200mV, not inconsiderable. And I get nothing like it if I touch probe anywhere else on amp.
