Jitter is dependant on the last out device to the DAC. How the DAC handles the jitter depends on the build quality. Bits are bits, period. Whether SPDIF or Toslink does not matter to the DAC. If there is electrical interference, that is a different ball game. If you are concerned about noise from the PC, you can put a ferrite core on the cable to the sound card. Use a Toslink or SPDIF cable to the DAC. That should eliminate the interference problem for the majority of users. The Red Book standard is 44.1 and the upsampling can be done with the external DAC. My Tri Vista 21 samples 96/192. Bit perfect output via my Chaintec 710 card has been verified by me. Foobar kernel streaming bypasses Windows Kmixer, as well as ASIO drivers. No need to get expensive sound cards, unless you are using the onboard DAC's from the card itself. Otherwise the external DAC is useless when using analog output from the sound card. Foobar is free and quite easy to set up. It is convienient when playing music, as it is all in front of you with just a click away.
PC built by me.
Tri Vista 21 DAC
Toslink connection
Levinson Pre
Levinson 33H Mono Blocks
Genesis 201 4 column speakers w/ 1000 watt Amp
SDI modded Apex DVD player and Sampo firmware
2 Ehome 8500 CRT's blended
One hell of a setup that sounds and looks fantastic.
MAK