I can almost guarantee you its something with either the RCA's, or the RCA connection at the amp. EXACT same thing happened to me when i had a PG Tantrum 1200.1 There was a constant, NASTY sound coming from just the subs. It was actually my terminal at the amp. When I shook it, it would go on and off, but hit real loud really quick.
Check the RCA's terminals on your amp.
Check the RCA's terminals on your amp.
