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 will be posting soon about this in my system thread, but suffice it to say that I have proven unmistakable and repeatable loss of resolution with complex material (Mahler 2nd) with simultaneous increase in glare, as the volume is lowered - yes, I feel digital volume controls and the inevitable loss of bit resolution are the predominant cause of these issues, with jitter second. Basically, once you start losing bits, it's impossible to properly reconstruct the signal - I now perfectly understand why Spectral, Schiit and others never did and never will offer digital volume controls.
On the other hand, finding a transparent preamp is equally challenging, and only with my 30SV (in RCA-in mode) have I been able to get the full RBCD resolution coming out of my modified Alpha... and my modifications are mainly responsible for enabling me to bring the digital volume control all the way up, to full 24 bits.
So with respect to your comparison, be sure to compare with the exact same digital volume control setting, and see if a preamp is still veiling things. I personally would never drive amps directly from a DAC, and though I have heard wider dynamics driving direct, pre-30SV, the sound was way off, because I was forced to lower the digital volume quite a bit.