Build a dual-channel audio amplifier from scratch using two LM386 ICs — no soldering required. A complete beginner-friendly guide with schematics, parts list, and step-by-step assembly.
An audio amplifier takes a weak electrical signal — from your phone, MP3 player, or computer — and boosts it enough to drive speakers. At its heart is an operational amplifier (op-amp) or dedicated audio power IC that increases the voltage and current of the input waveform without distorting it.
This guide walks you through building a dual-channel stereo amplifier using two LM386 Low Voltage Audio Power Amplifier integrated circuits. The LM386 is legendary among hobbyists: it runs on as little as 4 V, delivers up to 325 mW into an 8 Ω speaker, and requires only a handful of external components.
The LM386 is a class-AB audio amplifier IC in an 8-pin DIP package. Internally it contains differential input stages, a gain-setting network, and a push-pull output stage. Key features:
| Tool | Purpose |
|---|---|
| Breadboard (full-size, 830 points) | Platform for building the circuit without soldering |
| Jumper wires (assorted colors) | Connecting components on the breadboard |
| Multimeter | Verify voltages, check continuity, measure resistance |
| Wire cutters / strippers | Trim and strip jumper wires to length |
| Audio source (phone, MP3 player, PC) | Provides the stereo audio input signal |
| 3.5 mm stereo audio cable | Carries left/right signals from source to amplifier |
| 9 V battery with snap connector OR 9 V DC power supply | Power for the circuit |
The following table lists every component you need. Quantities are for a complete stereo amplifier with both left and right channels.
| # | Component / Part Number | Qty | Purpose / Role in Circuit |
|---|---|---|---|
| 1 | LM386N-1 — Low Voltage Audio Power Amplifier IC (DIP-8) | 2 | One per channel. The core amplifier chip. |
| 2 | 10 µF / 25 V electrolytic capacitor | 4 | Two for gain-setting (pins 1–8 on each LM386). Two as input coupling capacitors. |
| 3 | 220 µF / 25 V electrolytic capacitor | 2 | Output coupling — blocks DC from reaching the speakers. One per channel. |
| 4 | 10 µF / 25 V electrolytic capacitor (bypass) | 2 | Bypass capacitors on pin 6 of each LM386 to improve transient response. |
| 5 | 100 nF (0.1 µF) ceramic capacitor | 2 | Power supply decoupling — one per channel, placed close to each IC's VCC pin. |
| 6 | 10 kΩ dual-gang potentiometer (linear taper) | 1 | Stereo volume control — adjusts input signal level to both channels simultaneously. |
| 7 | 3.5 mm stereo audio jack (TRS, PCB-mount or panel-mount) | 1 | Audio input connector for your music source. |
| 8 | 8 Ω / 3 W speaker | 2 | Left and right stereo speakers. Small full-range drivers work well. |
| 9 | Speaker binding posts or terminal blocks | 4 | Screw terminals for connecting speaker wires to the breadboard (optional but recommended). |
| 10 | 9 V battery with snap connector OR 9 V DC wall adapter | 1 | Power supply. The LM386 operates from 4–15 V; 9 V is ideal. |
| 11 | Jumper wires (male-to-male, assorted colors) | ~30 | Breadboard interconnections. Use red for +V, black for GND, other colors for signals. |
| 12 | Full-size breadboard (830 tie-points) | 1 | The platform on which the entire circuit is assembled. |
| 13 | IC socket (DIP-8, optional but recommended) | 2 | Allows you to remove the LM386 without damaging it if something goes wrong. |
The LM386 comes in an 8-pin DIP package. Notch on the top indicates pin 1 (left side, notch facing you):
| Pin | Name | Description |
|---|---|---|
| 1 | GN (Gain −) | External gain terminal — connect to pin 8 via capacitor for 200× gain. |
| 2 | Vin− (Inverting Input) | Inverting audio input. Usually grounded in single-supply config. |
| 3 | Vin+ (Non-Inverting Input) | Non-inverting audio input — signal enters here via coupling capacitor. |
| 4 | GND | Circuit ground. Connect to the negative rail. |
| 5 | Vout (Output) | Amplified audio output — connects to speaker via coupling capacitor. |
| 6 | Cbypass | Bypass capacitor terminal. Connect 20 µF cap here to ground for better performance. |
| 7 | VCC (Supply) | Positive supply voltage (6–15 V). Connect to +9 V rail. |
| 8 | GP (Gain +) | External gain terminal — paired with pin 1 for gain setting. |
The schematic below shows the complete stereo amplifier circuit. The left channel (top) and right channel (bottom) are mirror images, each centered around one LM386 IC.
The diagram below maps every component to its position on a standard full-size breadboard. The left channel occupies the top half; the right channel mirrors it below.
Follow these steps in order. Work on one channel at a time — complete the left channel fully, then mirror it for the right channel.
Insert each LM386 so it straddles the center gap. The notch (or dot) on the top of the chip marks pin 1 — orient it to the left side. Pin 1 should be in row D, and pin 8 in row A' (bottom section). Leave a few rows between the two ICs for wiring clearance.
Connect the red (+) power rail on both sides of the breadboard together with a jumper wire. Do the same for the blue (−) / green ground rails. These will carry +9 V and GND to all components.
Pin 7 (VCC) on each LM386 → jumper wire to the +VCC rail.
Pin 4 (GND) on each LM386 → jumper wire to the GND rail.
Place a 100 nF ceramic capacitor between the +VCC rail and GND rail, as close to each IC's pin 7 as possible. This filters high-frequency noise from the power supply. The ceramic caps are non-polarized — orientation doesn't matter.
Connect a 10 µF electrolytic capacitor between pin 1 and pin 8 on each LM386. The longer lead (+) goes to pin 8; the shorter lead (−) goes to pin 1. This sets the internal gain resistor to maximum.
Connect a 10 µF electrolytic capacitor from pin 6 to GND on each LM386. Positive lead (+) to pin 6, negative lead (−) to ground. This improves transient response and reduces distortion.
Connect a jumper wire from pin 2 to GND on each LM386. This configures the amplifier in non-inverting mode, with all signal entering through pin 3.
The dual-gang potentiometer has six terminals (three per channel). Wire each gang as follows:
This creates a variable voltage divider that attenuates the input signal before it reaches the amplifier.
Connect a 10 µF electrolytic capacitor between the audio input source and each potentiometer's terminal 1. The positive lead (+) faces the audio jack side; the negative lead (−) connects to the pot. This blocks any DC offset from your audio source.
Wire your 3.5 mm TRS jack as follows:
Connect a 220 µF electrolytic capacitor from pin 5 (output) to each speaker's positive terminal. The positive lead (+) connects to pin 5; the negative lead (−) goes to the speaker. This blocks the DC bias voltage (~4.5 V at rest) from reaching the speaker coil.
The other side of each speaker (the terminal not connected to the output capacitor) goes to GND. If you're using binding posts or terminal blocks, mount them on the breadboard and connect:
Finally, connect your 9 V battery (or DC power supply):
Do not connect power yet — complete the verification steps below first!
Cause: Power not connected, volume at minimum, or audio source muted.
Fix: Verify +9 V is present on the VCC rail with a multimeter. Turn up the potentiometer. Check that your audio source is outputting sound (test headphones directly).
Cause: Ground loop between audio source and amplifier, or missing decoupling capacitors.
Fix: Ensure the audio jack sleeve is connected to GND. Verify both 100 nF decoupling capacitors are installed. Try a different audio cable.
Cause: Input signal too strong for the gain setting, or power supply voltage too low.
Fix: Reduce volume on your audio source. If using a battery, check that it's fresh (a weak 9 V battery may sag under load). You can also remove the gain capacitor (pins 1–8) to drop gain from 200× to 20×.
Cause: Loose connection on the non-working channel, or IC inserted backwards.
Fix: Check all connections on the silent channel. Verify pin 7 has +VCC and pin 4 has GND. Measure DC voltage at pin 5 — it should be ≈4.5 V.
Cause: Speaker connected directly to output (no coupling capacitor), short circuit, or output pin grounded.
Fix: Disconnect power immediately. Check that the 220 µF output coupling capacitor is correctly installed between pin 5 and the speaker. Verify no wire shorts pin 5 to GND.
Cause: Normal behavior with carbon-track potentiometers at high gain.
Fix: Use a higher-quality potentiometer (cermet or conductive plastic). This is cosmetic and doesn't indicate a circuit problem.