MP3 Player PCB (USB + uSD)

This mp3 player PCB (off eBay) was mine for the ridiculous price of AUD $2.29 including postage !

It’s possibly a good candidate for looping sound in a Halloween haunt, etc.

MP3 Player PCB










  • Micro USB socket for 5V supply (no data connection)
  • Stereo line level output via 3.5mm socket
  • Mono speaker output via screw terminal block
  • “Prev / V–” button: short press for previous track or long press for volume down
  • “Next/v++” button: short press for next track or long press for volume up
  • “P / P / Mode” button: short  press for the play / pause or long press for USB stick / uSD card mode selection
  • “Repeat” button: short  press for single / all track mode (no long press action)


A nice Lexar 32GB USB stick I tried didn’t work using either the 5V or 3.7V supply.  A cheap old 8GB one did though.

The board starts playback a few seconds after power-up if a suitable USB stick and files are found.

The stereo 3.5mm output is for line level connection to an external amplifier.  Due to the small coupling capacitors, hooking up headphones to this output will result in very thin sound (no bass).  Use the mono output (terminal block) if you want to drive a speaker directly.

Do not wire a battery to the BAT+ and BAT- terminals if you plan to ever plug the micro USB in as they are directly connected and mayhem (damage / flames) could ensue.

Bridging Out Speaker DisconnectDuring testing I noticed the speaker volume wavering intermittently. At first I thought it was a symptom of the battery voltage dropping, but changing over to USB 5V offered no improvement.

Nudging the contacts on the line out socket caused it to drop out even more. The 3.5mm socket disconnects the speaker output and the crappy contact was the source of the intermittent audio.

The quick solution is to simply solder a wire between the two pads (one either side of the socket) at the “tip end” of the socket.