Right, so I had some time with these boxes and here are some of my observation
Day 1
Slightly dark sounding with a a slight emphasis on bass
While the details were forthcoming and clarity was great, it sounded a little closed
Soundstage was not as wide as I expected but the depth was excellent
Day 2 onward
The slight bass emphasis had receded and overall tonality had lifted, resulting in a more noticeable opening sounding
No longer slightly dark sounding but largely neutral and rather clean sounding, but never in your face
Soundstage improved noticeably too, with good width to complement the excellent depth
The Vox has a rather big sound, I attribute this to the supercaps in the Zap
It is a great sounding DAC, largely neutral and very resolving and this allows the musical Sugden Class A and Monkey 93 to sing and express themselves