So the USB works in stereo and can be converted into other forms. Bad thing, when the USB cable is plugged in, my computer won't play out its normal speakers, even if the Pre-amp is shut off. Just a consideration for those who want to use it. The transmission was fine, but was limited by the quality of the MP4. I am not sure upsampling helped any on the MP4s. And yes, it worked with Itunes, so MP4s work.