Putting XM radio in the bronco. I want to hardwire the 12V power so I don't have to use the cigar plug adaptor. Looking at the provided cigar plug adaptor from XM, I note that it is labled, "DC to DC converter, Input 12v, Output 6v". So somehow the plug is stepping the voltage down to 6V? How do I snip the plug off and hard wire in to the truck?