.. USB interface audibly degrades the signal passing though it...
... it is a "packetized data" format in which data are split up into discrete chunks, wrapped up with information about those chunks, transmitted, and then put back together at the receiving end.
Dear Mr. Harley,
if it were really so, no one would be able to use a single external USB drive. So if there is any degradation, it is outside the USB interface. Unless of course it's a sales pitch.