External DAC

[gkkpch]

@mrv,
And... which DAC did you use? 

I'm using usb to SPDIF converter, with SPDIF to an AKM AK4458 DAC.

Sound over SPDIF is much better than using internal headphone output.
I've yet to test the difference between HDMI & SPDIF sound quality.

note for Ge... FLAC/APE files don't seem to play via the headphone out. Is that expected behavior?

Yes, but it is not a flac/ ape issue. As the headphone dac can't handle it, the music gets resampled. The problem is volumio's default bit rate does not work either, you need to change this in /etc/mpd.conf. Change 44100:16:2 to 44100:24:2 and you should be ok.