I posted this on another site but maybe I can get advice here, I have a 4ch rockford P400-4 set to 2ch and using two alpine 4ohm 6.5's. Everything had been working fine but lately say I am driving to work for about five minutes then I turn on radio you can feel the car kind of shudder a bit then after awhile of the radio playing the amp goes into thermal protect. The gains are under a quarter turn from zero and made sure the ground is good. Any ideas?