I'm trying to A/B between the two channels to use one for ryhtym and the other for lead.
However, when I switch between them:
a) There is a loud "pop"
b) There appears to be maybe a ground loop because one of the channels "hums".
You need an A/B box that grounds one lead when the other one isn't being used.It's like having a guitar cord plugged into the amp with no guitar;hums like a banshee.
So basically you need a better A/B box or modify the one you have.
You need two 3DPDT switches and wire them so when one channel is not used,that channel is grounded.
So one channel is on and the other is just like there was no jack plugged into it.
If you can't fathom what I'm taking about it might be just better to try a different A/B box.