guys, I tried this method and it worked. But, I get a hiss when hooked up to the cig lighter plug. I've grounded everthing and still hiss. I'll play my MP3 with its own power supply and its crystal clear. My portable DVD player with its own power battery pak its clear, once hooked up to cig lighter...hiss. Please help. Ive grouned it to radio chassis. Also tried pulling 12v power and ground from radio stuff and still hisss. This is reallying Hissing me off. ha thanks Ernie