[PROBLEM] Problem with an SMSL M300SE DAC

[Tim Curtis]

Such a quick response, I'm happy. 

@ Nutuil :The alsamixer shows x- default / x0- HDMI / Headphones (screenshot). Does that mean default is my DAC?

@ Tom Curtis & TheOldPresbyope: Yes, currently the HDMI port is selected. But I only have HDMI and headphone jack to choose from. 

This all looks to me like the device is not recognised as an audio device. Is that correct?

Try the command aplay -l

It lists all audio devices that Linux/ALSA have successfully recognized.