When multiple devices are connected to a single USB controller, each shares the controller s bandwidth. Hubs allow the physical connection of multiple peripherals to the USB controller. Hubs also provide power for peripherals. External hubs are connected to the USB port on a computer to provide additional ports. Active hubs provide 500 mA to each USB port.
Passive hubs divide power among the USB ports and are useful only for low power peripherals.
USBPre functions best when it is the only device connected to a host controller, giving it full USB bandwidth. USBPre must be plugged into either an active hub or directly into the PC, since it is a high power USB peripheral. Many peripherals, like USBPre, do not reserve USB bandwidth unless they are in use, so check with the manufacturer for specifics on a given peripheral. Some desktop and notebook computers have multiple USB controllers. With late model computers there is sufficient processing power to handle all of the tasks of computing along with audio.