I have an amp I use for my sub. For a long time now the sub will all the sudden start to hum really loud for no reason at all even if you are not using it. My connections seem fine but to get it to stop I either have to turn it off or wiggle the connector at the back of my denon 1610 receiver. I know I have a sort of audible ground loop hum that I have never been able to get rid of. Any ideas on what could be wrong?