LM386 Audio Amplifiers

Introduction

Amplifier PCBsMany hardware projects call for a small, self contained audio amplifier, from test speakers to adding sound effects to models. While low cost prefabricated boards from China are available for this purpose, it's more fun to take the DIY aspect of such a project further and build the amplifier yourself.

The LM386 mono audio amplifier IC is a good choice for this purpose. It's available in through-hole and SMD packages, requires a minimum of extra circuitry, and has a wide acceptable supply voltage range. I've designed two PCBs based on the LM386 schematic on TechLib.com: a mono amplifier, and a slightly larger stereo amplifier (essentially just two mono amps integrated on the same PCB).

These boards are best suited for projects that don't require hi-fi sound quality, but they produce perfectly adequate sound for the non-audiophile. I've used one in a computer speaker I built, and an LM386 was used in the AdLib (one of the first sound cards produced for IBM compatible PCs)

Technical Description

The LM386 is internally set with a gain of 20 (26 dB), but this can be overridden by external circuitry to increase the gain up to 200 (46 dB). More gain will increase the maximum volume, but will also increase the sensitivity of the volume control.

Since it's difficult to determine the right level of gain for your application before assembly, these boards allow for some experimentation. Start off with a gain of 20. If that isn't enough, install the components required for a gain of 50. To increase the gain further up to 200, connect the "Gain Switch" jumper(s).

To easily switch between 50 and 200, use PCB header pins and jumpers for the gain switches.

Configurations for the mono amplifier:
Gain = 20
Gain = 50
Gain = 200
Install R2?
No
Yes
Doesn't matter
Install C5?
No
Yes
Yes
Connect J5?
No
No
Yes

Configurations for the stereo amplifier:
Gain = 20
Gain = 50
Gain = 200
Install R2+R3?
No
Yes
Doesn't matter
Install C5+C10?
No
Yes
Yes
Connect J4+J6?
No
No
Yes

All connections to the PCB can be made with 2.54mm pin headers and DuPont cables, or you can solder cables directly to the PCB for a more permanent solution. A PCB footprint for a standard barrel jack power supply is also provided for convenience.

Downloads

Bill of Materials
    XLS spreadsheet, 18.5 KB - Contains a parts list for both the mono and stereo amplifiers.

Bill of Materials
    PDF document, 68.2 KB - Contains a parts list for both the mono and stereo amplifiers.

Stereo Amplifier Schematic
    PDF document, 130 KB

Mono Amplifier Schematic
    PDF document, 80.9 KB

Stereo Amplifier PCB Gerbers
    ZIP archive, 118 KB

Mono Amplifier PCB Gerbers
    ZIP archive, 66.9 KB

Stereo Amplifier KiCad Files
    ZIP archive, 459 KB - Useful if you want to make modifications to the stereo PCB. Made with KiCad 8.

Mono Amplifier KiCad Files
    ZIP archive, 387 KB - Useful if you want to make modifications to the mono PCB. Made with KiCad 8.

Thanks to Charles Wenzel of TechLib.com for designing this circuit.
Texas Instruments' LM386 datasheet (with handy reference schematics!) can be found here.

Last updated on Mar 3, 2025.
This page was first uploaded on Mar 2, 2025.
Background image by tile-anon.