The EP500 is connected on another outlet, different from my receiver. I have had the ground screw off since I first got the sub. Both the receiver and sub are connected with a Monster Cable power conditioner and the Monster power-sub conditioner. What I mean by mosquito noise is the sound of the radio receception being weak. It sounds sssshhhhh, as when you are trying to search for a radio station off the air. The sshhh sound goes away when the sub is off and the radio station sounds clear.

jj

Onkyo TX-SR805
M60T
EP500
VP150
QS4
Outdoor Algonquins