As you begin exploring the sonic possibilities of homemade pickups mounted on didgeridoos (Chapter 11) and drums (Chapter 9 and Chapter 10) and winding your own guitar pickups (Chapter 13), you might be a little hesitant to plug these monstrosities into your fully restored, vintage Vox tube amp. You could buy a cheap battery-powered amp (the RadioShack Mini Audio Amplifier, part #277-1008, is pretty homely but a good value at $15), but building your own is even cheaper—less than $2 if you scrounge up speakers and switches—and gives you good practice working with somewhat delicate components (like integrated circuits). The following circuit is a classic mini-amp built around the ultra-common, very affordable LM386 integrated circuit (IC); these sell for about a buck apiece, will drive any size speaker, and are hard to kill (but buy a few—we’ll build our project so that you can easily swap in a new chip if you happen to jostle or fry one). For more info on ICs, see the appendix.
This project calls for an 8 ohm speaker (so called because the coil offers 8 ohms of resistance). This is the most common speaker used in consumer electronics, from goofy little baby toys to $3,000 component sound systems; pretty much any speaker you scrounge out of a $1 garage-sale stereo will be an 8 ohm speaker. If it isn’t marked, you can test it with your multimeter (see the appendix for instructions).
