... decoder boardSingle Spectrum with balance display, SD Card, USB, FM RadioFeature & function: Single Spectrum with balance display, support USB/SD, MP3, ... to control external audio volume-Application: Ordinary audio combination, Car audio, multimedia speaker, subwoofer, amplifier, electronic products and ... any problems, please feel free to contact with us. R&D,mp3 decoder board for sd, usb,fm radio,LED