USB has no clock - it is an asynchronous protocol. If you use USB then you need to makes sure it handles 24 bits and the audio formats you need - that's all.
Jitter
- if you use USB then it all comes down to the clock in the DAC. (and these are all getting pretty good these days)
- if you use a toslink or SPDIF to feed to a DAC then you will undoubtedly have some jitter as most PC's or Imac devices have jitter and an "interface" tends to create jitter. In this case it boils down to the re-clocking algorithm's in the DAC and it may be important to choose the DAC accordingly. If you have a preferred DAC and it is not well regarded for excellent jitter immunity then a "pace car" would be anoher way to go.
As Detlof says - there is no reason you won;t be able to get excellent sound PROVIDED you get bit transparent data to the DAC (watch out for pitfalls in Digital volume controls, equalizers and just general software bugs...for example some verisons of iTunes are good if you know the proper settings and some versions are actually flawed.)
Jitter
- if you use USB then it all comes down to the clock in the DAC. (and these are all getting pretty good these days)
- if you use a toslink or SPDIF to feed to a DAC then you will undoubtedly have some jitter as most PC's or Imac devices have jitter and an "interface" tends to create jitter. In this case it boils down to the re-clocking algorithm's in the DAC and it may be important to choose the DAC accordingly. If you have a preferred DAC and it is not well regarded for excellent jitter immunity then a "pace car" would be anoher way to go.
As Detlof says - there is no reason you won;t be able to get excellent sound PROVIDED you get bit transparent data to the DAC (watch out for pitfalls in Digital volume controls, equalizers and just general software bugs...for example some verisons of iTunes are good if you know the proper settings and some versions are actually flawed.)