I spent a few hours with this unit today, and tried it with about 8 pairs of headphones. My setup was Macbook Pro -> Audirvana Plus v2 player -> rPAC The unit is very simple - no display or indicators, just plug and play. Feels nice in the hand too, small but solid. I was really pleased with the combination of the Audeze and the rPAC, which was articulate and perfectly balanced and natural. It had enough power to drive the Audeze and Beyerdynamic T5p easily but some phones needed maximum volume to get loud and I think it was the Hifiman HE 560...