The Infinity Gold amp is expecting low level input. If you unplug the end of that cable from your radio, you can just tap into the wires for the inputs. If you get a 9V battery and one of those little things that snaps on the top to give you a pos and neg wire you can test it by sticking them into speaker pairs. If you hear a pop, you've got an output channel. If you don't hear anything, you've got an input channel. That make sense?