The aim is to get SPDIF stream (for external DAC) with the best quality
(I mean all kinds of jitters). Of course, such hardware must be ALSA-supported.
Needed formats are stereo streams with 32KHz-96KHz rate and 16 and 24 bit depth.
And, of course, such interface must have own dedicated power supply unit
to be completely kept from PC power rippling. Needed operation is playing back
only (without capturing).
With googling it is possible to find (probably) suitable hardware, but all I
have found are over-featured and, as a result, over-priced regarding needed