[NAVY IC]

I know cars are chassis grounded, and ships are floating grounds, but they have the same symptoms...
i have guys chasing grounds on the ship everyday, mostly by isolating procedures, (like you did w/your amp)...
re-check all of your connections and wires, make sure everthing is tight, plugged in and all of the insulation is intact...
the remote wire being pinched is a good ex. of a "grounded" ckt, be dilligent 'cause it's usually something like that, small and inconspicuos...