Build a Stereo LM386 Audio Amplifier

What you’re building

The LM386 is a small monaural power-amplifier IC: it raises a low-level audio signal enough to drive a modest loudspeaker. Stereo is two independent mono amplifiers—one for left, one for right—with a shared supply and ground. Each channel’s output is AC-coupled to its speaker by an electrolytic capacitor, keeping the chip’s DC bias off the speaker.

↗Signal path

3.5 mm stereo input → separate 10 kΩ volume pots → coupling capacitors → LM386 inputs → output capacitors → 8 Ω speakers.

⌁Expected result

A simple, useful desktop / experimenter amp for small speakers. Output is modest and depends on supply, speaker, and signal; it is not a high-power or hi-fi amplifier.

Design choice: The gain pins (1 and 8) are left open, giving the LM386 its default voltage gain of about 20. This keeps the build less hiss-prone and more stable than the optional gain-200 configuration.

Safety & prerequisites

Power safely. Use only a current-limited low-voltage DC supply or a fresh 9 V battery for this build. Never connect a breadboard circuit to mains voltage. Disconnect power before changing wiring; electrolytic capacitors are polarized.

⌕Workbench & tools

Solderless breadboard and insulated jumper wires
Digital multimeter (voltage, resistance, continuity)
Wire cutters/strippers; soldering iron is optional, not needed for the breadboard
Audio source with a 3.5 mm stereo lead; start at low volume
Two small 8 Ω speakers (not headphones)

◇Know before wiring

Identify the LM386 notch/dot and count pins counter-clockwise from the notch.
Read capacitor markings: electrolytics have a marked negative stripe; ceramic capacitors are non-polar.
Breadboard rows connect internally; power rails may be split in the middle.
Use one common ground for input, both ICs, supply, and speaker returns.

Keep the two speaker wires for each channel paired and away from the input wires. Excessive volume, clipped audio, or shorted outputs can overheat the IC or drain a battery quickly.

Complete parts list

One stereo build; values shown are practical starting points.
Component / part	Qty.	Purpose / notes
LM386N-1 low-voltage audio power amplifier, DIP-8	2	One mono amplifier per channel. Use DIP package for breadboard; verify pin-1 notch.
Solderless breadboard, full-size	1	Temporary construction platform; check whether the red/blue rails are split.
Jumper wires, insulated	~20	Power, ground, signal, and cross-row connections.
10 kΩ audio-taper potentiometer (linear works)	2	Independent left/right volume. Three terminals: input end, ground end, wiper.
10 µF electrolytic, ≥16 V	2	Input coupling: wiper to LM386 pin 3. Positive end faces pin 3.
220 µF electrolytic, ≥16 V	2	Speaker output coupling from pin 5; positive faces the IC output.
10 µF electrolytic, ≥16 V	2	Local bypass from pin 7 to ground; positive to pin 7. Recommended.
100 nF (0.1 µF) ceramic, ≥16 V	2	High-frequency supply decoupling; one close to pins 6 and 4 per IC.
220 µF electrolytic, ≥16 V	1	Bulk decoupling across the shared 9 V and ground rails near the ICs.
10 Ω resistor, ¼ W + 47 nF ceramic capacitor	2 each	Optional Zobel network, in series from each pin 5 to ground; helps output stability with real wiring/speakers.
8 Ω speakers, 0.5 W or greater	2	Small speaker loads, one per channel. Do not substitute a short or a load below 8 Ω.
3.5 mm stereo audio lead / jack	1	Tip = left, ring = right, sleeve = common ground (check your cable).
9 V battery + clip, or regulated 9 V DC supply	1	Positive to VCC rail and negative to common ground. A supply with current limit is preferable.

The 220 µF speaker capacitors and 10 µF input/bypass capacitors are polarized. If yours are rated exactly 16 V, they are suitable for this 9 V circuit. Optional Zobel parts are included for robustness; the core circuit can be tested without them.

04A

Schematic · one channel, duplicated

LM386 mono stage × 2

Build identical left & right circuits; share only supply, ground, and source ground.

Pin numbering is from the top view of a DIP-8 package with the notch at the top: left side 1–4 downward, right side 5–8 upward. Pins 1 and 8 are intentionally unconnected.

04B

Breadboard wiring map

Two ICs straddling the center trench

Illustrative placement—not to scale; follow pin/row labels.

Breadboard rows vary by model. This is a connection map, not a promise that every visible hole shares the pictured row. Check continuity on your breadboard and connect each labeled pin to the named rail/node. Keep pin 5 outputs separate.

Step-by-step assembly

Power off; map your board.
Disconnect the battery/supply. Use the multimeter’s continuity mode to identify connected tie rows and any split power rails. Mark a +9 V rail and a common ground rail.
Place both LM386s across the center trench.
Seat each DIP-8 so four legs are on either side of the trench. Orient both notches the same way. Identify pins 1–8 from the notch; confirm pin numbers against the schematic before adding wires.
Make the shared supply and grounds.
Connect the positive supply rail to pin 6 of both ICs. Connect pins 4 and 2 of both ICs to the ground rail. Keep pins 1 and 8 open. Do not connect power yet.
Add supply decoupling.
Place one 100 nF ceramic capacitor close to each IC, between pin 6 / +9 V and ground. Add the 220 µF bulk capacitor across the rails: positive to +9 V, negative stripe to ground. If rails are split, jumper the halves together.
Wire the bypass pins.
For each IC, place a 10 µF electrolytic from pin 7 to ground, positive lead at pin 7. This helps suppress supply-related noise; do not confuse pin 7 with the output at pin 5.
Wire the two volume controls and inputs.
For each 10 kΩ pot, connect one outer lug to its channel signal (tip for left, ring for right), the other outer lug to ground, and the center lug (wiper) through a 10 µF input capacitor to pin 3. Put the capacitor’s positive lead toward pin 3. Connect the audio cable sleeve to common ground. Leave pin 2 grounded.
Connect the speaker outputs.
For each channel, wire pin 5 through a 220 µF electrolytic to that channel’s speaker positive terminal; the capacitor positive lead faces pin 5. Connect the speaker’s other terminal to common ground. Never connect a speaker directly between the two IC outputs. If fitting the optional Zobel network, wire 10 Ω in series with 47 nF from pin 5 to ground.
Inspect before power.
Check every pin and capacitor polarity against the diagram. Ensure the +9 V and ground rails are not shorted; confirm the two pin-5 output nodes are not joined. Turn both pots fully down and unplug the audio source.
Power and bring up the sound gently.
Connect a 9 V battery or set a current-limited bench supply to 9 V with a conservative limit (about 200–300 mA for initial checks). Verify supply polarity and voltage at both pin-6 nodes. Connect the audio source at low output level, then slowly raise the volume.

Testing & troubleshooting

Before you switch on

✓Supply is 9 V DC, correct polarity

✓Pin 6 gets +V; pin 4 and pin 2 go to ground

✓Electrolytic stripe / polarity checked

✓8 Ω speaker on each separate output

✓Input sleeve, ICs, and supply share ground

✓Volume at minimum; audio source unplugged initially

First power-up: With speakers disconnected, power the circuit and measure the DC voltage at pin 5 of each LM386 relative to ground. It should sit around half the supply (roughly 3–5 V on a 9 V supply). The 220 µF output capacitor blocks this DC from reaching the speaker. Power down before reconnecting or moving wires.

No sound in either channel

Check battery voltage, the common ground, pin-6 supply, audio cable sleeve, source output level, and that pin 3—not pin 2—receives the coupled signal. Verify the rail isn’t split.

Only one channel works

Swap left/right input leads to isolate the source from the amp. Inspect that channel’s pot wiper, input-capacitor polarity, pin-5 output capacitor, and speaker wiring.

Hum, hiss, or oscillation

Use short input wires and a common ground; keep input wiring away from speaker/output wiring. Confirm local 100 nF decouplers are close to the ICs, add the Zobel network, and avoid excessive gain or volume.

Distorted sound / hot IC

Lower source and pot volume; clipping is common when pushed hard. Check for an output short, wrong speaker impedance, reversed electrolytics, incorrect pin orientation, or a supply above the part’s rating.

Pop, crackle, or intermittent audio

Reseat the ICs and jumpers, check pot connections and breadboard contacts, and inspect for loose speaker terminals. Power down before adjusting wiring.

Unexpected DC at speaker

Check the 220 µF output capacitor is in series and positive toward pin 5. Do not connect a speaker directly to pin 5. A multimeter should show near-zero DC across the speaker after the coupling capacitor.

Stop if anything gets hot, smells, or draws unexpectedly high current. Disconnect power, let capacitors discharge, and recheck pin orientation, rail shorts, capacitor polarity, and speaker load before trying again.