IC vs. S/PDIF?

One has a 75 Ohm spec and one does not. One comes in pairs and one comes as a single. Both typically have RCA's though some have BNC's. How does a cable producer change the spec on what outwardly appears to be an identical cable? If you specify from a cable producer that you want an S/PDIF how do you know they are not simply selling you one half of a pair of off-the-shelf IC's? And last but not least, how does 75 Ohm change the sound one would hear from a normal IC (when carrying digital signal rather than analogue of course)? 
I know this much; a very well-respected engineer with a Ph.D. in EE who designs and produces DAC's of his own says that you are free to experiment with using a normal IC with his DAC's rather than a dedicated S/PDIF. 

Showing 1 response by mesch

I believe that when source and input impedance is to be the same, as with connections between digital devices, the term is 'match' when source is to be low and input device is to be much higher, as between analog devices the term is 'bridged'. The 75ohm coax and 110ohm XLR are for matched situations. Analog ICs are for bridged.