The hardware is simple: A 16850 lithium-ion battery powers an MP3 Decoder/Amplifier module that plays MP3s stored on a Micro SD card. A speaker, power switch, and micro USB powered battery charger ...

Sound comes into the unit through an off-the-shelf Bluetooth module, before being passed to an ADAU1401 digital signal processing unit. From there, it’s passed to a mono amp to drive the woofer ...