Just installed Volumio today and had this issue with my HIfimediy DAC
It wasn’t easy to find an answer so I hope this could help anyone has this issue.
the DAC was connected to usb but no sound from pi.
I had to do this to make it work:
sudo apt-get update
sudo apt-get install git-core
sudo apt-get install binutils
sudo rpi-update
sudo rebootnow it works like a charm.