The amplifier inside a million kit speakers
The LM386 minimum parts amplifier, the chip inside countless kit speakers, with a volume knob and a terminal for a small speaker.
Free build sheet
The parts, every wire with its length and bend points, a bend guide, both sides of the board and checkboxes to track your progress. Print it or keep it open at the bench.
Open the build sheetWhat you need
10 parts on a perfboard 17 × 30 holes, plus hookup wire.
| Qty | Part | Where to buy |
|---|---|---|
| 1 | Electrolytic Cap100uF C1 | Buy Electrolytic Cap on Amazon |
| 1 | Electrolytic Cap10uF C2 | Buy Electrolytic Cap on Amazon |
| 1 | Electrolytic Cap220uF C3 | Buy Electrolytic Cap on Amazon |
| 1 | Ceramic Cap47nF C4 | Buy Ceramic Cap on Amazon |
| 1 | Power Input (2-pin) J1 | |
| 2 | Screw Terminal 2P (5.08mm) J2, J3 | |
| 1 | Potentiometer Q1 | |
| 1 | Resistor (axial)10R R1 | Buy Resistor (axial) on Amazon |
| 1 | DIP-8 U1 |
Check every pin against the datasheet of the exact part in your hands before wiring.
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Cut list
17 wires, 445 mm (17.5 in) in total, in the order the build sheet cuts them. Wire numbers match the build sheet. Each length includes 5 mm per end to go through the hole.
| Wire | Colour and net | Length | ||
|---|---|---|---|---|
| 12 | BlackGND F9 → E14 | F9 → E14 | 24mm | 15mm (45°) |
| 6 | BlackOUT J20 → E21 | J20 → E21 | 25mm | 8mm (90°) |
| 5 | BlueOUT H20 → H17 | H20 → H17 | 18mm | Straight |
| 11 | BlueGND D5 → H5 | D5 → H5 | 20mm | Straight |
| 17 | BlueGND N24 → F25 | N24 → F25 | 33mm | 8mm (90°) |
| 10 | GreenGND E4 → E8 | E4 → E8 | 20mm | Straight |
| 4 | GreenBYPASS J15 → E18 | J15 → E18 | 30mm | 13mm (90°) |
| 16 | GreenGND K17 → M25 | K17 → M25 | 35mm | 25mm (90°) |
| 1 | RedSPK D23 → D25 | D23 → D25 | 15mm | Straight |
| 13 | RedGND I6 → L8 | I6 → L8 | 23mm | 13mm (90°) |
| 7 | RedWIPER K10 → F14 | K10 → F14 | 33mm | 18mm (90°) |
| 3 | WhiteZOBEL J24 → L23 | J24 → L23 | 18mm | 10mm (90°) |
| 15 | WhiteGND J16 → H15 | J16 → H15 | 18mm | 10mm (90°) |
| 9 | White9V B4 → F18 | B4 → F18 | 56mm | 41mm (90°) |
| 8 | Yellow9V C3 → I3 | C3 → I3 | 25mm | Straight |
| 14 | YellowGND L10 → L16 | L10 → L16 | 25mm | Straight |
| 2 | YellowIN J8 → C8 | J8 → C8 | 28mm | Straight |
About this build
The LM386 minimum parts amplifier, the chip inside countless kit speakers. It runs on 9V and needs very little around it.
A 10k volume pot feeds the chip's input. On the way out, a 220uF capacitor couples the output to the speaker terminal, so the speaker gets the audio and no DC. A 10 ohm resistor and a 47nF cap across the output form a Zobel network, which keeps the amp stable with a real speaker on it.
A 100uF cap on the 9V supply and a 10uF on the chip's bypass input round it out. Which chip pin goes where is on the build sheet, checked against the TI LM386 datasheet (SNAS545).
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