Fresh up to date install and solus shows my soundcard but no audio is output when I test the speakers.
I also have an AMD rx580 but its hdmi audio does not show as an option. Worked perfect under xubuntu and works fine under win7 dual boot so I know everything else is fine.
I want to output to the m-audio card. Is there a way to blacklist hdmi audio just in-case this is causing the problem.
Partly fixed my own problem. I have installed the package alsa-tools since I needed envy24control. The volume was set to zero in this app so it seems solus does not by default set the audio at 100% even though the settings show it as such. My only problem now is that on reboot it keeps reverting to back zero under envy24control so I need a way set some default for alsa.
Have you tried looking if your soundcard shows up in alsamixer?
The solution was
install alsa-tools
run envy24control and bring the levels up from 0
sudo alsactl store
It may be of help to others with cards from the m-audio delta family. Please mark as fixed.
I'm a user of M-Audio Delta 66 and I had the same problem on all distros, and i disliked the alsa-tools package because it gives me a few other apps alongside envy24control that i never use, so instead of installing alsa-tools what you really do not need to is go to the terminal and type alsamixer which is installed by default on all linux distros, then press F6 to select the sound card, and bring the DAC0 and DAC1, exit the alsamixer and alsactl store ... problem solved 
I really dislike that PulseAudio which is now used as the default sound system in most distros doesn't have an option to manipulate channels of these type of sound cards ... would love to hear some feedback if anyone ever succeed in doing so without using the alsamixer
