I'm trying to understand how the CD changer works. considering that the head unit is able to read files and folders on the CD, it would seem to imply that the CD changer is acting as sort of a hard drive that just supplies raw data to the head unit, which the head unit in turn decodes from MP3 or WMA data to produce audio. The CD changer doesn't actually produce audio, right?? If this is the case, couldn't I conceivably create some sort of hard drive based device that supplied data to the head unit, which the head unit would "think" is a CD changer?

That would be an iPod. :D

ya, but even the IPOD, using the AUX input is not going to be near the quality as a line level input into the head unit.

I'm trying to understand how the CD changer works. considering that the head unit is able to read files and folders on the CD, it would seem to imply that the CD changer is acting as sort of a hard drive that just supplies raw data to the head unit, which the head unit in turn decodes from MP3 or WMA data to produce audio. The CD changer doesn't actually produce audio, right?? If this is the case, couldn't I conceivably create some sort of hard drive based device that supplied data to the head unit, which the head unit would "think" is a CD changer?

the CD's have embeded data in them that allows the H/U to display the information. (EX: Audio CD's sometimes have artist / album / track data embeded in the CD, so that it is displayed on the head unit. MP3 CD's are data, so the H/U just reads that data and displays it)

The changer it self, more than likely, does not actually produce audio. I am guessing that it reads the CD, and sends the information to the H/U and that is what produces audio. Theoreticly, you probally could remove the changer and put in a Hard drive. But you would have to find out how to hook it up (probally need a EE/CE/CS degree to figure it out and make it work) It is probally more trouble than its worth, and for the time and money you would probally be better off buying a new H/U that is hard drive based. but that is just my opinion....