FWIW, when I had a 200, I never thought that vocals sounded indistinct as you describe, nor heard anyone say that their D was weak in this area. That is definitely not one of Devialets weak points.
There must be something wrong with the amp, or it is not set or hooked up correctly, surely.
Alex.
try to reset to factory default, and install new firmware version + configurator settings.
I had a simular issue, and this did the trick for me.
It's a very different sound. My naim unit now sounds confused and muddy next to the devialet. The devialet is very accurate. Break in is essential. Initial hours were disappointing. It's now astounding with the Atohms.
How did your comparison go? My 130 sounded disappointing out of the box, but with 100+ hours on it was transformed.
I'm afraid I'm back with Naim. I couldn't quite deal with the sound of the 120. I did audition a 220 and it blew me away - unfortunately couldn't afford it, but will certainly move in that direction when I can!
OK, Nothing wrong with Naim!