An amplifier is the most basic and essential tool in electronic music. There are dozens of amplifier chips available these days, ranging in power from fractions of a watt like the LM386, suitable for battery power, to high-power integrated circuits intended for use in hi-fis, TV sound systems, or car stereos. This circuit puts out about 1/4 watt of audio power and can be used to drive small speakers or headphones. It runs nicely off of a 9-volt battery or a set of four AA batteries. By adding a 10 uf capacitor between pins 1 and 8 the gain rises to 200, which is more suitable for contact microphones, coils, and guitar pickups. Especially in the high gain setting, this one is susceptible to oscillation. At less than a dollar retail, this chip, combined with few other components in a very simple configuration, makes cheap but decent low-power audio amplifier. It is heart of many commercial mini-amps. And it’s almost indestructible.