This applies to the Audiohub 2×4

We recommend using the mains power supply with Audiohub for optimal performance and to avoid unwanted audio artefacts. Optimal audio streaming performance and loud headphone levels cannot be guaranteed on all computers without the use of the included power supply.

It is possible to use Audiohub 2×4 with only USB bus power, however you may find that the Audiohub has some limitations in this case:

• You will be unable to use the USB hub on the device.
• When using low impedance headphones with high output levels, it's possible to experience audio dropouts.