Battery-powered amplifier

This is a battery-powered amplifier based on the LM386 chip, with an input buffer fed to the inverting input. The input buffer helps preserve the high-frequency details entering the LM386 chip. It is powered by a 9V battery.

The amplifier architecture has been updated, employing an input buffer to feed the inverting input, and the volume control has been changed from an output rheostat to the type and location shown in the datasheet application note. Furthermore, the 5k gain potentiometer has been reduced to 1k. The input buffer helps preserve the treble detail entering the LM386 chip. As you increase the volume, you'll begin to experience good overdrive performance.

The gain potentiometer acts like a limiter for the amount of gain available. By carefully setting the volume and gain potentiometers, you can get the clearest volume from the 386. To do this, set the volume potentiometer to maximum and then slowly increase the gain potentiometer. Find the point just before the sound begins to overload; you've got the maximum clear volume available. To get into overload mode, increase the gain potentiometer to the desired maximum gain and adjust the volume potentiometer. These potentiometers are highly interactive. If you set the gain potentiometer high but still don't get the desired overload, you must increase the volume potentiometer to allow more signal to pass through the 386.

The buffer is specified to use an MPF102 FET, although the 2N5457 would provide similar results. The J201 also works, but with slightly lower output.