The LM386 is a low voltage chip making it ideal for a battery operated device. It has a OpAmp built in. See the image below for the pin layout. When pin 1 and pin 8 are not connected the gain is 20 but this can be increased to 200 if a 10uF capacitor is placed between these pins. Pin 4 and 6 provide supply voltage for the chip. Pin 3 is the input and a potentiometer connected to it will act as a volume control. Pin 5 is the output and can be connected to a speaker.
There is plenty of literature and schematics on the LM386 on the internet. For now I choose the one used by HackaweekTV on YouTube (https://www.youtube.com/watch?v=3KyBrAoHMX8). It uses a 10K potentiometer for volume control and a 10uF capacitor to increase gain.
Only a few components were needed so building it on a breadboard was straight forward. While testing it the amplification is excellent and the music sounds ok. Next time I will try to improve the circuit.
|Pinout diagram of the LM386|
|Schematics of HackaweekTV used for this experiment|
|Circuit on the breadboard with the audio jack and the speaker. On the left the 100uF smoothing capacitor.|
|Close-up of the LM386 and the connections to all the components.|