. With Ultra-low distortion amplifying circuit.Description 2 . With aux input for non-Bluetooth devices. 3 . Built-in battery for outdoor activities, when the adaptor interrupts the power, the machine will intelligently switch to the built-in battery for work continuously. 4 . Built-in MP3 encoding supporting U disk, when reading U disk, the encoding system will engage in encoding playing，according to the generation sequence of MP3 songs file. 5 . With independent volume control of bass , treble, main volume, guitar volume, Mic volume, Echo.