as one last test, unplug the RCA's from your HU and plug them into something else that has RCA outputs.. it could be anything, even a home stereo and just hook it up in the garage.. see if the problem is still there. If its gone than you know it has to be the source.

2000 SVT Black/Tan #1633/2150 (a few mods) Alpine: CDA-9835, MRV-F540, MRD-M550 PG: TANTRUM-X 6.5 COMP all around. Some people wear Superman pajamas. Superman wears Chuck Norris pajamas. CEL currently: Off