A word of advice to Yggdrasil owners upgrading to Unison USB: if you make a stupid mistake like I just did with the (complete PITA more so than the 5,436 4-40 screws that hold the case together) ribbon cable that connects to the front display, and you stupidly miss an entire row of pins when fumbling with your too-large hands to get it back in place, the Yggdrasil will power up normally but you will not be able to select the USB input. This will, of course and completely logically, make you think that OHMYGOD the brand new release-version Unison card is bad when in fact it is operator error. Don't be silly LIKE ME and reach out to Schiit for help when in fact it is a mistake made by you. Just calmly remove the 5,436 screws for the twentieth time and properly install the ribbon connector, perhaps using a flashlight to see that it is fully and properly engaged, and then reassemble the Yggdrasil.
It works like a charm when you put it together properly. Trust me, I know.