Audio Science Review of Expert 200.

[Confused]

Looking at the Paul Miller measurements for the D170 (page 5 of this thread) I spotted something that I found quite intriguing.

For the USB input:
Signal-to-Noise Ratio (A-weighted, 3rd-Octave mode) into 8ohm = 97.3dB

For the SPDIF input:
Signal-to-Noise Ratio (A-weighted, 3rd-Octave mode) into 8ohm = 117.7dB

Reasonable measurements both, but I am intrigued by the20dB difference between the USB and SPDIF input.

Subjectively, a few of us have observed in the past that we prefer the sound via AES/EBI with the "pre-Pro" Expert. In my own case, I preferred the Aurender N10 via AES/EBU, rather than via USB, and I preferred my microRendu via the Mutec MC3+USB, AES/EBU out, rather than via USB direct. OK - many variables here, but it does make me wonder what the above difference in S/N ratio makes to sound quality. Is there a correlation? Or maybe it is the myriad of other factors that lead to the subjectively observed difference in sound quality? Possibly a bit of both?

I am also puzzled at the 20dB difference in the headline result number, when the associated figures in the table below look far more similar. Can anyone explain or interpret this? I am at the "a little knowledge is a dangerous thing" level, when it comes to interpreting the detail here.