I also found that the d54250wyk nuc chopps up all 5.1 audio over hdmi when running ubunutu 13.1 (most recent) and the most recent mint (16). Stereo output over hdmi works correctly though. Both of these operating systems output correct hdmi 5.1 audio on and older intel chipset (jetway board) so its something specific to the nuc and perhaps the 5000 chipset.
Anyone have any ideas why NUC 5.1 audio does not work with linux? Even the intel whitepaper on xbmc presumes this works but it does not.
Everything else seems to work fine (ethernet, video, etc) , just the 5.1 audio.