Signal noise problem

OK, i've re-done my sketch with expanded areas and everything is included so that you can see what's going on. This is almost as good as a picture, maybe even better.

How can I break the ground loop for this?

I am worried that the problem is in the “D” cable/"3" connector and the power plug it is attached to. If you don’t already have one, pick up a power polarity tester. Verify that it is correct at the wall and at the internal power strip. Also check the amplifier, especially if the amp is using a different wall outlet. If something is backwards in this area you have a potentially fatal situation that only requires one other thing to go wrong before you start playing “Come on baby, light my fire.”