There are several remedies for audio that is distorted, choppy or otherwise compromised:
- Hot plug the interface (unplug the USB or Thunderbolt cable, then plug it back in)
- Toggle sample rate (in your DAW or, in the case of iTunes, Audio MIDI Setup)
- Reload DAW driver (for example, in Logic choose Logic Pro Preferences Audio. Click on the Devices tab, then the Core Audio tab. Uncheck Enabled, then re-check it.
- In iTunes, stop then re-start audio playback.