Audio Systems: car stereo feedback, noise filter, input gain

Question
When I hook my amp up to any of my speakers, I get a rumbling noise in the background accompanied by a whistling noise when I rev up the engine, until I turn it up loud enough to drown out the sound.  It used to be the rumbling without the whistling.  I think the rumbling is a bad ground.  It doesn't do it when I just turn the key on.  It only does it when I start the engine.  Will a sound compressor take care of whistling?  

Answer
Casey,
Your amp is picking up noise from the alternator on your engine. You may want to install a heavy duty noise filter on the output of your alternator. The filter will need to pass or handle the current rating of the alternator. As for the rumble noise, try turning down the input gain on the amp. Please contact me direct for more info about a noise filter.

TOM,
T&D ELECTRONICS
tdeser@zoominternet.net