No listening with eyes or with notions of materials used I'm afraid. This graininess is conspicuous in its absence. Upsampling CD players impart their own sheen-like texture to the sound which is audible through valve amps but not through solid state. Messing with sampling rate settings on my Bel Canto CD2 I can also impart the same sheen on the 192 compared to the 96 or 48 settings through my valve amps.

Natural musical textures i.e. the harmonic structure of instruments that enables you to identify the particular instrument (or even particular guitar pick-up) are clearly audible where this inherent grainy texture, the one stamped all over every sound passing through solid state amps, is absent.