hopsing
+1y
Or, is he hearing clicking through his speakers? If so, check your stereo grounds and make sure they are all good. Like Ricky said, the diodes are used to prevent power backfeed through the switches when your hooking up multiple switches/valves, but are using only three prong switches. (instead of using a six or twelve prong to operate multiple valves) Look at the AVS boxes, they use all three prongs with diodes.