RF Punch 200a4 Noise

Well, I have punch 200a4 that is making some humming noises. I have tried these things to try and fix it. Changed RCA wires, moved ground location, changed ground wire and tried. Ground has been sanded to bare metal. These noises persist. Only on this amp does this noise occur. I have a Kicker amp that I put in its place with all the same wires, just swapped amps and the noise isn't present. Then I put the punch amp back in and the noise was there. Is there anything I am missing here?