“The Raspberry Pi Zero (and Zero W) are amazing devices for such a low cost. But they are missing one feature needed for many projects. That is sound. The only audio they have by default is via HDMI TV monitor. They support “earphone” audio, but lack the jack and audio filter circuitry that the bigger Raspberry Pi’s have. I wanted simple audio, good enough for speech and sound effects, but not necessarily high fidelity. There are plugin modules for adding sound (including high quality stereo) available, such as this one: https://www.adafruit.com/product/3346 but I was after something simple from spare parts I already had. This describes a one transistor mono amplifier capable of driving a small speaker and providing decent sound, much better than just a buzz or beep. All that is needed are a few resistors and capacitors, a 2N2222 NPN transistor and a small speaker. It runs off the Raspi’s 5V power and only needs 3 wires to connect to Pi.”