[clevermax]

I have this USB pedndrive mp3 -> FM converter which I plug in to my car's cig. lighter jack, and I just turn on radio in my headunit, and tune to the frequency displayed in the transmitter. The pen drive is of course plugged into the USB host of the transmitter before plugging in the transmitter to the cig. lighter jack.

FM sound quality, pen drive electrically and mechanically isolated completely from th HU! I can even give a direct audio output to the transmitter.