Kij - Async USB is quite immune to jitter from the USB signals, however it is not immune to jitter caused from noise on the ground or the power wires in the cable.
This is why USB cable common-mode filters like the Short-Block are so effective:
http://www.empiricalaudio.com/products/short-block
I also now have a USB filter and power supply combo called the Power-Block. If your USB interface needs the 5V power, such as the Berkeley converter and others that have galvanic isolation, the Power Block can make a big difference in SQ:
http://www.audiocircle.com/index.php?topic=128620.0
The cable is still important in either the case of the cable-powered or device-powered USB interface.
Steve N.
Empirical Audio
This is why USB cable common-mode filters like the Short-Block are so effective:
http://www.empiricalaudio.com/products/short-block
I also now have a USB filter and power supply combo called the Power-Block. If your USB interface needs the 5V power, such as the Berkeley converter and others that have galvanic isolation, the Power Block can make a big difference in SQ:
http://www.audiocircle.com/index.php?topic=128620.0
The cable is still important in either the case of the cable-powered or device-powered USB interface.
Steve N.
Empirical Audio