No it doesn't work with the NAD. I wish it does. I have the x-sabre on loan and was not able to get it to work either. The ZX1 does works with my Pico DAC, PS Digital link III, and Matrix Mini-I Pro though. I'm not sure what the catch on sending digital over USB really on the Sony. I'm perplexed why the F887 does work with the X-sabre and the ZX1 doesn't.
It's sad to hear that. I have no idea why the f887 worked with x-sabre since it was another member who reported it.
By the look of it, m51 can not be feed by usb otg since I tried a lot of android phones and none of them work. I suspect it has something to do with the nad's usb driver.
zx1 is so close to a perfect all in one unit with android, streaming, otg, form factor and lod to use with pico power and yet...