Thanks Technic. To disable BT audio on the iPhone before connecting, how do I do that? Do you mean turn off bluetooth functionality altogether (phone and audio?). Or is there some way to do that in the settings on the iPhone itself before it connects? Perhaps hitting that blue symbol in iTunes before connecting USB.
Do you happen to know why I might be getting distortion when playing over USB connection only? I see the ability to change the gain staging for the aux port in the options, but I thought USB only would be decoded by the stereo itself.