Got a fliptronic board that works fine, but makes the speakers buzz when the end-of-stroke voltage is activated. That kind of makes me think there's something up with the 12v, but as far as I can tell, Fliptronics II boards don't actually use the 12v they get. No buzz with a rottendog board, although there is a constant slight hum regardless of what board is in there. Sound board is properly grounded. Ideas?