radone

I just received my DD-1 today and cant wait to use it. I have two questions after reading the manual. If I'm testing just a headunit thru the rca connection do I have to use a y-cable for each set of rca's or just the left or right rca or do I need to check all 6 rca connectors? When testing a headunit through an amplifier do I need to disconnect the speakers? Thanks