If you get noise in the subs. My guess would be you might have an open ground shield on the rca jacks either inside the amp or in the head unit. Theres 2 ways on how to tell if the rca ground shield is open 1 way is with a multimeter. The next way is take a piece of wire and ground it to the amps ground terminal and the other end touch the outer rca shield with the ground wire to see if the noise goes away .