If your head unit only has the one RCA out, chances are it is a subwoofer output. This is all well and good if you only have the intention of running a sub with your amp. In this case, you just connect the single RCA from your head unit to the white RCA (left channel) on your amplifier. It is common practise to use the white RCA for mono. It appears you amp has black instead of white (which is fine), so connect to the black if this is the case. If you plan on driving speakers with your amplifier, you will have to go and purchase a line out converter (also referred to as a high to low converter) to enable you to drive your amp from your current speaker outputs. Hey I'm just running my sub off my amp which is a Sony xplod xm-zr604 but my head deck has only a brown RCA plug which is labeled subwoofer out on the plug and also in the manual. So I guess I use any of the black or red RCA plugs that came with my wiring and plug it into the sub out on my head deck and the other end to my amps white RCA plug. Please correct me if I am wrong oh and btw do I need the REM cable aswell. Where do I connect that to on my head deck that is my only other problem? thanks for your help Justin