I've got an Audio FX DAC-X6 and the Cynanogen Audio-FX app recognizes that through USB OTG like this:

http://i.imgur.com/4wheOfV.png

However nothing plays audio through it, no apps, not even Kodi with passthrough enabled, nothing will play music through the DAC. I've even tried installing Viper Audio Engine that didn't work either. When I use music apps like AIMP, Foobar, and the native Cynanogen one it plays the song with no sound outputting anywhere but it is actually trying to play the song, judging by the progress through the song.
I've updated to the latest nightly and nothing seems to want to make it work. I've also disabled the option to prevent audio playing through the USB in the developer options, also tried with and without ADB, rebooted with it plugged in and out and various other configurations.

I have also tried using my friend's Zenfone 4 with a Stock Asus ROM which works perfectly fine every time.

Does CM13 just not support DAC/USB Audio yet or is this a bug?

Not sure what kind of logs to attach for this kind of thing but I can try find them if they would be helpful towards fixing the issue.