I had this type of problem before also, When my amp was grounded to the body chassis the installer didn't clean it up and just bolted it on.

Had to take the ground off and grind the surface fairly well and the popping went away.

I also think amps shouldn't be grounded to factory bolts anyhow, Correct me if I am wrong?

 

if a portion of the amp internals (+ voltage) touches the case then the case should not be a safety hazard to the owner, I thought they had to be grounded but I am not certain (this isnt NEMA/ UL/ IEC/ IEEE)

 

Well i just found that one of my RCA shield on the amp ISNT grounded. So i grounded it but i still have the same problem. I havent tried grounding the AMP body yet but thats what i'm going to do next. If one the RCA shields ins't grounded, does that mean that something inside the amp is wrong?

 

I just went to ground the amp body, before i did i tested to see if it was already and it is. So with that one RCA not grounded internally, does that mean that its screwed?