Are there differing qualities of optical cable?

Jitter is not additive if you have a properly designed asynchronous DAC.

Again it is the equipment design and build which is key and not the cable. Incoming jitter becomes irrelevant if you have a DAC that ignores it.

@willemj

The interface is indeed the issue and it depends on the methodology of implementation.

I would argue that USB digital has been a disaster for many years.

Even today day I think the approach can be worse than Coax or Toslink because of logic induced modulation noise induced back into the power supply of the USB DAC.

Does it matter - absolutely! Non random Jitter is quite audible even at picosecond levels. Check out Cranesong website for some jitter demonstrations.

It shouldn't sound different unless the DAC is not handling jitter very well in which case you may need to experiment to find out what works best in your situation.

I assume you are playing CDs which should be fine. Just avoid using this DAC for any higher than 18 bit files as it probably just truncates and throws out the least significant bits on any digital music above 18 bit.