Can anyone recommend a good electronics repair shop in or around the philly area? Im getting engine noise through the speakers, that increases as the engine revs. The humming only affects the 4channel amp (subwoofer is not affected). Im assuming i just need some grounds fixed on the rcas. Head unit is a pionner avic d2. I just dealt with an incompetant shop in nc while i was home for a few weeks, so im eager to get this taken care of once and for all. Thanks for the help!