Beaglebone & NAD M51

Recently i purchased a beagblebone black rev c.
I have successfully mounted volumio and am able to connect to my M51 dac (N20 in list) via usb.
I am able to send music to the dac evidenced by a change in bitrate on the dac display depending on the file bit rate chosen.
But no sound. I have tried most if not all options including disabling hardware volume control etc but no luck.
Is it simply that the M51 is not compatible with volumio or with beagblebone as a device?
Will a hdmi cable work?