This is an easy-to-build 5-watt Practice Amp, based on the 16 pin LM384 IC. You supply the speaker (almost any speaker will do). The amp is the same power amp as one of the small Marshall practice amp power amp stages. This project can be used as a modular building block to a full featured practice amp,or is great by itself with any stompbox between the guitar and amp (can sound dull with passive guitar pickups straight into it).

Description from General Guitar Gadgets.