I notice noise from speakers after i add a boss 400w x4ch amp. It's for my 6x9's & 6.5's. I replace the alt, because i was told it is gettin' weak. I got a new alt, that didn't work so i redid the ground wire, it's under the rear seat i used the nut that holds the flip back of the seat. My brother in law & i are out of ideas.

 

are power and signal wires running on different sides? or at least 18 inches apart??

 

also, were did you run the RCAs? I have had some bad luck in the past with the transmission throughing noise into RCAs from them being to close. and in case anyone was wondering - i did not run them outside the cab.

 

im not quite sure where you are saying you grounded the amp. but you should try just directly bolting it to the metal of the car. sand off all the paint and stuff first though