This minimal component audio amplifier schematic is taken almost in its entirety from the LM386 datasheet but with the component values adjusted to more readily available values. None of them are critical.

The electret microphone input stage is added as an equally minimal input device. The 47K resistor supplies the bias current for the microphone and the 100nF capacitor blocks any resulting DC from passing to the amplifier.

This circuit can be run from a six volt battery supply, such as four AA cells, or from a six volt DC power supply. The actual voltage is not critical, it should work from four volts upwards, but it is recommended not to go higher than twelve volts or the LM386 may be damaged.

The circuit is laid out on the breadboard in roughly the same arrangement as in the schematic. The speaker used was an old PC speaker so a pin header was inserted into the breadboard to accept it. The connection for the microphone is also shown as a pin header in the layout diagram but the electret actually used to build the circuit had wire ends so a header wasn't used.

Speakers don't much care which way round they are connected, if the connections are reversed all that changes is the phase, but they are usually marked + and - and it is good practice to always connect the + lead to the signal and the - lead to 0V.

Electret microphones are polarised and will not work connected the wrong way round so you must connect the + lead to the amplifier input and the - lead to 0V.

The + end of both the speaker and microphone connections are marked by a red stripe in the layout diagram.

The 22K volume pot only had short leads so tinned wire was soldered to each so that it would plug into the breadboard. If the volume pot works in the reverse sense, i.e. turning it clockwise makes it quieter, then fitting it rotated 180 degrees should correct this.

Here the is circuit laid out and working on an actual breadboard.

This is just a small section of a much larger breadboard. The extra components are capacitors that I usually have scattered across the breadboard to eliminate noise from the power rails. They make no difference to this circuit.

The extra links are because this particular breadboard has a break in the horizontal rails at the mid point. I don't want this break so I usually keep these positions jumpered.