I can't seem to find which package it's in but when I had one of those I used envy24control to set it up -- it could be muted by default or be set to output to digital not analogue (or vice-versa).
If you can't find envy24control you could try the plain old alsamixer and check the settings there. If you've got pulse Audio installed you'll want to install the pulse audio tools to and use the volume control.
The card definitely works under Linux as I've had one working to output both analogue and digital and a friend uses one for recording and mixing.
Edit: envy24control is in alsa-tools-gui if you're using a Debian-based distro.
Last edited by 273; 04-09-2013 at 11:11 AM.