- pioneer head unit with RCA frnt and rear outputs hooked up to phillips amp in trunk, which in turn is hooked up to the frnt door speakers and rear-deck speakers - amp is directly conected to the battery in the trunk (by 12 gauge wire and fuse) - speakers in the rear doors are connected directly to the head unit - The (loud) squeal occurs when both RCA channels are connected to the amp - if I unplug one or the other channels from the amp the sound disappears - It seems that the two RCA circuits are interfering with each other - Will rewiring the RCA connection so both channels have a common '-' wire (correct the problem?