and is it possible to have something causing one even if it only uses a two prong plug? I think my sub is causing a ground loop resulting in a wave going up my plasma screen when it hits a certain frequency (like 60Hz). I have read that a ground loop can be a buzz or a stationary or moving horizontal line on a display. Is this true? If my sub only has a two prong plug, is it possible it is still causing a ground loop?