Arcam USB DAC 23425 - Manual (Page 7)

Windows 7 looks a little different, but the goal is the same, to ensure that the Arcam device is the only device connected to the Enhanced USB controller:
MacOS X:
All of the above comments about connections are equally valid for OSX. To determine which USB device is connected to which controller, go to “Apps” > “Utilities” >
“System Profiler” > “USB” Below is an example from an OSX system.
Once you have found the ARCAM device, you can see that this is the only device on the “High-Speed Bus” controller.