Originally Posted by Duartisimo
I am sorry, not knowledgeable at tech stuff... USB Hub?
An example, please? Because somehow i get the feeling you maybe talking about a kind of surge protector type device.
He means an external multi-connector USB expansion device. Typically, these come with 4 to 8 additional USB connection outputs. The distinguishing factor is which of these devices (there are hundreds of types) come with their own power supply for the USB.
One of the important qualities of the USB protocol is that it contains a 5V power supply in USB connections and cables. Typically, that 5V power comes from the power buss in a PC. With most desktop PC's, the power is not an issue. Even with multiple USB peripherals, there's ample current to supply whatever USB is hung off the buss. However, in some laptops and I guess an Apple MAC, the USB power from the motherboard is not sufficient. Hang a few peripherals (or just one that needs significant power) off of the buss and then there's not enough current left to properly supply the devices.
The market for USB "hubs" includes many models that come with their own USB power, typically in the form of a 5V switching wall adapter that can supply several Amps of power for the hub.
Bottom line, if the external DAC does not have sufficient current requirements, it may negate all the clean power devices in the DAC (regulators) and result in significant sound quality degradation.