Stereo FM transmitter from MP3 player

Not so long ago, a Chinese manufacturer developed this device for the lucky owners of cassette tape recorders who do not have enough money to buy a normal MP3 player.

Cheap and cheerful - it’s relatively cheap (I got it for 200 rubles), but it has a number of advantages, including a remote control. It's simple: plug it into the cigarette lighter, plug in a flash drive with your favorite music, tune the radio to the transmitter frequency and that's it! Click on the remote control without touching it with your hands from a distance.

I don't have a car, but I decided to use this little thing in my own way. Like a stereo transmitter. Why do I need this? And in order to broadcast sound from a laptop to a music center. The fact is that I like to watch movies on the big screen, on a projector. I connect the video directly from the laptop, but to connect the sound you need to pull a long wire to the center. To avoid this, I decided to get rid of the wires in my own way.

I bought it and took it apart. Having made a kind of bunch of parts.

The device is divided into two parts: a small board is a stabilizer.It reduces the voltage to 5 volts and stabilizes it accordingly. There are 3 wires going to it: two power wires and the third antenna (white in color). A large board with a display is the MP3 player itself.

We solder all three wires from the large board. In place of the antenna wire, we solder a longer wire to increase the transmission radius. We take a USB adapter and solder power from it to the board as shown in the figure.

Next, we connect the sound to the transmitter. We find the transmitter chip. Sound from the processor comes to it through two chip capacitors. We remove these capacitors, I just carefully knocked them off with a screwdriver. The work is painstaking. We solder two capacitors with a nominal value of 0.01...0.1 μF to the output of the microcircuit and apply sound to them. We take the common wire from the minus of the board. That's all. It would be nice to add a resistor divider to each input, say 1:2, otherwise the laptop’s output is higher voltage than necessary. But then I realized it.

Close and check. Works!

Very comfortably! Our transmitter is also powered by a laptop. The quality is certainly not the same as through a wire, but quite decent. Now you can only change the transmitted frequency from the remote control, the rest has lost its power. I think there is nothing complicated here, anyone can do it themselves with a little effort without major problems.