In essence, it is the external sound card of the USB interface such as mini USB amplifier, which has increased functions like power amplification and adjustment than the ordinary sound card. USB sound box transmits the digital audio signals from the USB interface of the main board to the sound box directly, then the built-in D/A conversion circuit processes the signals and output the signals. USB sound boxes can improve the sound quality, because the digital signals will not be disturbed in the transmission process, and the purity of the signals is good. As the core of the USB sound box is the D/A conversion circuit, its conversion precision has a great influence on the performance of the sound box.
Traditionally, the power amplifier interfaces are mostly made of optical fibers, AUX, coaxial interfaces, and the newer one, HDMI, but many computers do not have these interfaces for users who use PC to form home theater. Aimed at these computer users, some manufacturers have developed USB interface power amplifier with built-in USB decoding chip, that is, using a public USB line to connect the computer and power amplifier directly, so as to output the USB line source codes to the amplifier for Dolby and DTS decoding, which can solve the trouble that many users’ computers do not have optical fibers and coaxial interfaces.