turkayguner
100+ Head-Fier
Then you should just get a quality CD player and use the S/PDIF connection to your DAC.... if you're hearing variations and degradation in tone from USB. If you're so fussy about absolute sound quality, you should move away from PC. Get a quality transport or streamer and use the best connection type into your DAC... in my case the AES into Yggy.
It is not about me. The OP asked if he/she should pick S/PDIF or USB. My personal experiences and the knowledge which can be found over the internet easily tells that it is wiser to go with S/PDIF if you have the option.