I've been meaning to try this out for a while, and finally got around to it, but lo and behold I plugged my iPad (64GB 3G) into a USB dac to see if it works, and it does. See where the volume slider should be running the iPod app?
Here's a pic of the USB connector (that comes with the official Camera Connection Kit):
And, yes, the eq presets also work:
Works great.
All we need now is for Amarra or Channel D to make a nice audio engine app for the iPad.
