sound quality: Onboard 2W amplifier (5V power of up to 3W) directly connected to the speaker; recommended to use 43W speakers. Audio output and input: 3.5mm goldplated headphone port supports headphones or external audio devices. MP3 playback: Supports MP3 format with automatic playback; when MP3 is playing the red LED flashes. Disk and memory card playback modes: Disk (tested 32G) and Memory Card (tested 16G) play modes. Power defaults to Memory Card modes; if the card does not exist automatically jumps to the Disk modes. If both devices are installed, you can manually set the play modes. For detail please see the key operating instructions. User controls: Buttons can be used to go up and down to control songs, adjust volumes up and down, pause or play, and switch modes. For detail please see the key operating instructions. Use scenarios: At home or in the office, pair with external speakers or use headphones via the 3.5mm port, loading MP3s on a Memory Card or Disk. On the go, play music from Memory Card (16G tested) or Disk (32G tested) without needing an internet connection. Small gatherings or events can connect to an external speaker system via the 3.5mm port for background or foreground music, using the appropriate play mode.