The sound from my asynchronous USB DAC (Meridian Explorer) sounds considerably more terrible with Volumio than with XBMC. I can’t explain that, but it sounds like the sound is less pure, less clean on Volumio, as if some bits are missing in, or added to, the stream.
This issue is related to problems of the USB bus of the Raspberry Pi. It results in packets drop (the problem you described) when big amount of data are sent via USB. It happens especially with Async Dacs, cause they normally ask for 32 bit data, which trigger this problem (adding bits, means adding zeroes to the datas, but not changing it).
It doesn’t happen with XBMC because it probably resamples it to 44\16, not triggering the problem. Volumio instead is working in bit perfect, so the problem arises.
Solution: use a different platform, or the pi 2 (I’m testing it against this issue as we speak).
In spite of my nickname, I am currently using the Cubox-i2. 
I also believe the Meridian Explorer plays bitrates natively, so, if I am not mistaking, when I play 44/16 it will ask for 44/16?
As the rest of the hardware of the Pi 2 remains the same, do you think that the Pi 2 makers a difference? Or is it the newer kernel or drivers? I wonder of updating to a Pi 2 could help solving my async USB dac issues.
As I mentioned, I experience the same problem with a Cubox-i2.
MMM, ok. That helps.
I will investigate on the cubox-i and report back soon (I hope)
I´m owning a CuBox-i4Pro and an ODAC (the thing which was developed by NavGuy) asynchronous DAC and everthing is working very well.
I have no issues at all with sound quality. The ODAC is directly connected via USB to the CuBox. Till now I have tested 16/44.1 to 24/96. Even If I use a USB-HUB to connect the DAC everything works fine. No drop outs, no noise, just cristal clear sound.
from9to5
ODAC is not async…
Mea culpa! My mind was screwed up! 
Of course it´s not asynch.
from9to5
Today, after a long while playing with XBMC and Kodi, I switched back to Volumio, for XBMC an Kodi stutter considerably. With Volumio, the stutter is gone, but the sound is more harsh (it kind of ‘hurts my ears’). Is this possible? With Kodi the sound is smoother, though when playing all day my ears get ringing too. I have to try Volumio some longer to tell.
It sounds as if Volumio is mangling some (minor) bits, resulting in high-frequency distortion. I hear it scrunch in my ears. Kodi didn’t have that. Is this possible?
Maybe there should be some option to play in 15 bits to remove watermarking…