I hard-wired my
iPOD to the back of my CDR-220 today with the kit from discountcarstereo.com. It includes a power and ground wire to supply a charging voltage to the
iPOD, as well as the speaker connections for the back of the head unit.
Once installed, the cable plugs into the bottom of the
iPOD. It works great, too, but I can hear the
iPOD through the stereo. You can hear the hard drive portion accessing data between songs pretty easily as a high-pitched squeal. It's not alternator noise, as it doesn't vary with RPMs. It's also no intolerably loud, but noticeable.
Any way to remove the noise? Sounds like the cable is just insufficiently shielded.