Another homemade.
The idea came spontaneously, low-power PAM8403 amplifiers appeared, there were extra lithium-ion batteries and charging controllers with voltage stabilizers. I decided to try to assemble a small portable speaker. It was the portable speaker that was the first experience for me. Before that, I collected ordinary passive speakers. Amplifiers were purchased for the repair of small computer speakers and seemed to want to try something with headphones. Computer speakers will then be repaired quite a lot, but with the headphones it has not grown together, so far probably.
In general, in fact, 2 charge controllers are connected in parallel at the input and output, several batteries from old unnecessary smartphones and phones are permanently connected to them. Then, through the switch, the voltage goes to a voltage regulator with a USB output, for connecting various USB gadgets or charging phones. And through the second switch, the amplifier itself is already powered. A 3.5mm stereo jack is used for audio input. The sound at the input is regulated by a variable dual resistor (like 10kOhm or so), the outputs from the amplifier are connected to the speakers, respectively. The sound is not a fountain, but for a quiet background listening or watching videos from YouTube on the phone is enough. With fully charged batteries, you can immediately charge the phone and listen to music via AUX. You can also connect a bluetooth transmitter to the USB and remove the analog audio output to the amplifier from the transmitter. The column is obtained already with the bluetooth function. Such here craft, was done just for the sake of experiment, but it has already found application for a long time.
Write in the comments what you think about such a trial portable speaker.