I'd agree entirely, though naturally you can have a slightly different sonic flavour without losing on quality imo. See for example the V200. It's actually not a neutral amp, and has some colour in both the sub bass and upper mids to give it that ever so slightly more engaging texture, smoothness and oopmh, without drowning out details.
With the X-DAC as well for example. USB is more detailed and airy, with sharper high emphasis and an overall cleaner or more transparent sort of sound (very neutral and I'd imagine quite accurate). I doubt there's much jitter mind, not that I'd know but sonically speaking, there's no real grain, noise etc, and the highs and vocals still maintain sweetness inherent in the T1's.
Through optical, by contrast, I'd imagine there is some intentional colour similar to that of the V200 and certain tube amps. There's more sub bass extension, smoother high's, increased mids, more warmth and musicality. There's not really less detail per se, but because of the stronger lows, it is harder to make out details than compared to USB by a tiny fraction, but a trade off always has to be made with these things.
When you get to this sort of level, adding one element of emphasis or another to sound signatures always affects others, the skill in design is to ensure the adverse or counter effects are negligible or still beneficial. That's why I believe the V200 was designed with extended upper mids as well as sub bass, to balance out the mood and ensure it didn't end up too dark.
Originally Posted by project86
Ok, good point, how about we say "equal in quality if not identical in sound signature"? Basically we are trying to avoid a situation where USB is clearly inferior to the other options, likely due to poor jitter control. Think DacMagic (version 1).
Edited by Naim.F.C - 2/6/12 at 5:51pm