3 possible reasons:
1) USB interface jitter is higher
2) SB3, particularly with mods has lower jitter
3) the playback software you are using with the USB interface is compromised. If you are using for instance iTunes on a PC, this is what you get.
You have only scratched the surface of the most important thing in all digital audio systems, the clock jitter.
This only gets better. Try reclocking the SB3 or upgrading your USB interface with a USB converter.
Try playing back from a PC with Foobar2000 and Jplay plug-in.
Steve N.
Empirical Audio
1) USB interface jitter is higher
2) SB3, particularly with mods has lower jitter
3) the playback software you are using with the USB interface is compromised. If you are using for instance iTunes on a PC, this is what you get.
You have only scratched the surface of the most important thing in all digital audio systems, the clock jitter.
This only gets better. Try reclocking the SB3 or upgrading your USB interface with a USB converter.
Try playing back from a PC with Foobar2000 and Jplay plug-in.
Steve N.
Empirical Audio