1. The Reason of cancel the external power adapter and use USB powered.
2.Many devices (e.g. Computer TV DVD) USB ports output stable voltage and current, And filters some bad waves. So the DAC( Digital to Analog audio converter) will works better, And decode will more stable.
3. In addition ,Use USB output power that is more environmentally friendly, And reduce costs, And compatible with all country.
4. This item NOT convert Dolby.