I originally thought that all head units with iPod dock connectors retrieved songs off the iPod digitally and then decoded them (sort of like treating the iPod as an external Hardrive). This would presumably be higher quality than using an AUX connection, because it would be digital instead of analog.

But then I saw a post that said many car head units still grab the songs as analog even if its using the dock connector. Is there a way to tell which head units grab the songs digitally and which units grab them as analog?