Based on the specs, it seems that the DAC supports it's full throughput using USB 2.0.
You may however have an issue with the USB hub in your motherboard being overworked, or having USB 1.0 items plugged in. If you have a single USB 1 device I believe everything on the hub has to throttle down.
Assuming you have a desktop, you might want to consider a separate USB card, but USB 2.0 should work.