Funny you should bring that up today... just last night I emailed a friend why digital volume controls SUCK, including the one in the Vivaldi 2.0 that I had in for evaluation (though to a lesser degree - I suspect they interpolate more and more as the volume is lowered, up to a point). (...)
I have a different view on this aspect -in my system and opinion the Vivaldi volume is excellent, if used within its correct range. The Vivaldi can change the output in 4 discrete levels (.2, .6. 2, and 6V full range) and we usually do not need large attenuation in normal use. As I prefer the sound with a preamplifier, and I can attenuate volume in the DAC compensating it increasing the gain of the preamplifier. IMHO within 12-15 dB there is no easily noticeable difference in sound quality between both modes.