GSD22 and a fusion radio with JBL amp. All wiring is semi close but done by someone else. Turn the 4208 on, no feedback. Power up the GSD and there is a low decibel static thump heard through the speakers. Does not increase with volume. I've separated wires and no change. The sounder to Trans cable does run through the hull bottom along with the rear speakers but the sound is through the front speakers and wires are no where near each other.