Here is a Radio Shack throwback. An mini, self-contained, mono amplified speaker. Very handy for audio work. As typical for electronics from the last century (circa late 1970s), the schematic for the device was affixed to the inside back of the case:

There is a volume adjustment, single stage transistor amp and an LM386 op amp amplifier. On the side is the volume/on/off switch, input and output mono audio jacks. At some point I plugged the output jack so I wouldn’t confuse it with the input jack and get frustrated there was no audio out.

Inside is straightforward and you can see the LM386. I’m bad and not using the recommended Radio Shack 9V battery (as I can’t get them anymore or use my Battery of the Month card).

That’s it! I still have it and it comes in very handy for things like amplifying audio from microcontroller digital to analog converters (DAC) and other circuits. Most people now might use an old PC amplified speaker – that works also, this was a precursor.

On the heels of #SepTandy, Adafruit is celebrating #ShackToberFest, a celebration of all things Radio Shack and Tandy. Tag your social media posts #ShackToberFest!