I really am a music guy & not a computer/techie guy. So, considering that the digital information that runs from the DAC to the Preamp is 1's & 0's or bits & bytes or whatever they are called; how critical is it to the sonic perfromance that I use an elaborate digital cable, as I have done with my analog interconnects?
Apart from clocking issues...I really can't see how it can make a difference. Either the bits all arrive or some of them don't.....you will soon know if some don't as you may get some nasty pops or clicks.
As for clocking.....a cable, being a passive device, physically cannot add "jitter". Length and electrical properties will of course modify the absolute timing and shape of the clock signal but a constant shift is NOT of concern, as audible jitter issues come from VARIATIONS in the clock signal between ticks. Furthermore, some jitter is not a problem provided it is small enough and random....i.e NOT influenced by some highly correlated influence such as oscillations in a power supply with bass response or induced correlated RF noise from somewhere.
Jitter is more component related than cabling. Changing from optical to SP/DIF might make a difference but the cause is most likely due to RF interference or the accuracy with which components either generate or interpret these two different signals.
If your clock signal is accurately re-clocked in the DAC (rather than a slave to the transport) then you have nothing to worry about (except your DAC)
....just my two cents.