Is there a difference in sound between a coax cable and an optical one?

shtinkydog, nobody can answer that, since it is system dependent.  Optical should be better, because it does nor create ground loops and is not sensitive to any electrical ambient noise, but on it is very susceptible to a system noise. System noise, on either makes threshold point variable - not only in amplitude but also in time.  Uncertainty in time is jitter.  Jitter is noise. Going to coax helps, because transitions are 10x faster, but fast transitions create standing waves in the cable (reflections) that alter timing.  Nobody can tell you what is better.  They can tell you only what worked better in THEIR SYSTEM.  You have to try for yourself.

In theory, optical is better as there can be no chance of ground loops. Ground loops CAN manifest in the digital and analog domains.

In the first, it can produce significantly more jitter, and was for a time a significant source of issues with PC/laptop based systems when powered from the AC. Batter power and better isolation seem to have taken care of most of this, same for USB.

There has been some claims that the receivers just tend to be better for coaxial, but also conflicting claims that coaxial receivers are often not optimized for S/PDIF.

In any event, I use USB for it all now. Sounds good, and much higher bandwidth.

Good point, @three_easy_payments

I had forgotten about the bandwidth differences.

Best,

E

Try signal to noise ratio. 

There are soooo many variables. Coax output, cable, and input implementation etc. Same with optical variables. Do experiment with what you can and use what sounds best to you.

In my own rig after trying 3 coax (silnote, HF Reveal & Acoustic Revive DSIX active) and 2 optical cables (both plastic & glass), on both types both with and without an ifi spdif ipurifier, coax bested optical for both music and video. Since my DAC uses no muting, using the ifi caused a loud zap every time I switched sources (node2) so I left it off. The active AR coax cable sounds most musical and real to me on everything. Good luck!