Difference in sound between copper and silver digital cables?

Because the OP was asking specifically about copper vs. silver would be my guess.

But you could start another thread just for that :-)

I don’t reckon optical cables have ever beaten copper or silver digital cables for sound quality. Which you have to admit is mighty curious. On the other hand I haven’t been paying much attention the past 30 years or so. Especially since I stopped using interconnects and digital cables completely about 3 years ago. 

None whatsoever

What is the audio signal? What a terrific time to ask this question again, no?

If a digital cable is used, the only thing that matters is whether the bits are transmitted.  Being degraded before hitting the cable is irrelevant, because whatever bits are transmitted is all the question deals with.  Read  The Skeptic  Audiophoolery, for analogue arguments.