earnmyturns
Headphoneus Supremus
Jitter shouldn't be an issue. USB, however, doesn't send a continuous signal, but is far more complex. Supposedly all the negotiation between components causes the USB chips to generate noise, which can leak into the DAC and cause distortion, hence why audiophile players that hog the USB connection are supposed to improve the sound quality.
While electrical and protocol protocol details are very different between asynchronous audio USB and S/PDIF, both can introduce jitter. In the S/PDIF case, the ideal square wave signal put out by the sender gets munged in transmission, affecting leading edge detection and thus timing. For accurate D>A, you want samples to arrive to the DAC at exactly the right time. In my ideal world, no matter whether the digital input is USB, S/PDIF, AES/SBU, or whatever, it would be buffered and reissued to the D>A proper synchronously with a very accurate clock. I've read a lot of gear descriptions for DACs and for USB>S/PDIF or USB>/AES/SBU at many price points, but they typically do not provide precise details on the different data paths (for instance, on how clock is handled in USB vs S/PDIF for DACs that accept both).