BeginnerAudio
LM386 Mini Audio Amplifier
Make a small mono speaker amplifier and learn input coupling, gain, decoupling, and speaker polarity.
Parts from the database
- LM386N-1 × 1Low-voltage audio power amplifier
Other supplies
- 8 Ω speaker rated at least 1 WCommon build supply
- solderless breadboardCommon build supply
- 10 kΩ audio potentiometerCommon build supply
- 10 µF electrolytic capacitorCommon build supply
- 220 µF electrolytic output capacitorCommon build supply
- 100 nF supply bypass capacitorCommon build supply
- 3.5 mm audio leadCommon build supply
- regulated 6 V supplyCommon build supply
- jumper wiresCommon build supply
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Connections
- Pin 6 to +6 V and pin 4 to ground; place 100 nF close between pins 6 and 4.
- Pin 2 to ground. Feed the audio signal through the volume potentiometer and a 10 µF coupling capacitor to pin 3.
- Leave pins 1 and 8 open for the lower default gain in the first build.
- Connect pin 5 through a 220 µF electrolytic capacitor to the speaker; the capacitor positive side faces pin 5. Return the other speaker lead to ground.
Build steps
- Build on a breadboard and keep the input lead away from the speaker/output wires.
- Check the IC notch and pin numbers, then verify the electrolytic capacitor polarities.
- Start with the volume turned fully down. Apply a quiet audio source and raise the volume gradually.
- Once it works, compare the sound with and without longer input leads to hear how layout affects hum and oscillation.
Software and firmware setup
This is a hardware-only circuit; no firmware is required.
Test your build
A clean small speaker output is expected, not room-filling volume. TI specifies about 325 mW typical into 8 Ω from 6 V at 10% THD; at lower distortion the usable output is less.
Troubleshooting
- No sound: check that pins 4 and 6 have ground and supply, and that the audio source shares ground.
- Loud hum: shorten input wires and add the 100 nF capacitor directly at the IC supply pins.
- Distorted sound: lower the input level and volume; do not use a speaker below the rated load.
Safety and limitations
Keep to the specified low-voltage supply and a small speaker. Do not ground either output of a later bridge-tied amplifier; this project is not bridge-tied.
Manufacturer and platform documentation
Community Notes for This Project
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