Beginner+
Mini Amplifier
Assemble a small battery-powered audio amplifier for a speaker or test bench.
Safety first, always.
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Breadboard amplifier
Build an LM386 mono amplifier from individual parts and understand every pin in the audio path.
Bench time
90 minutes-3 hours
Typical parts
$20-$40 AUD
Power
6-9 V battery
You finish with
0.25-0.5 W mono bench amp
Before the first wire
Know the build before you power it.
Use a genuine LM386 in DIP-8 and orient the notch before any wire is placed.
Start at the default gain of 20 by leaving pins 1 and 8 unconnected.
The speaker must connect through the 220 uF output capacitor because pin 5 sits at a DC bias.
Keep the input wiring short and away from the speaker/output loop.
Bill of materials
10 parts groups to gather
Check every spec
| Qty | Part | Exact spec | What it does | Inspect before use |
|---|---|---|---|---|
| 1 | LM386N audio amplifier | DIP-8, suitable for 6-9 V supply | Provides voltage and current gain. | Notch/dot marks pin 1; verify the suffix datasheet. |
| 1 | Solderless breadboard | Half-size or larger | Holds the first prototype. | Know which power rails are split in the middle. |
| 1 | Volume potentiometer | 10 kohm logarithmic preferred | Attenuates the input signal. | Find the centre wiper using resistance mode. |
| 1 | Input coupling capacitor | 100 nF-1 uF film/ceramic | Blocks source DC from pin 3. | Non-polar type keeps orientation simple. |
| 1 | Output capacitor | 220 uF, 16 V electrolytic | Blocks pin-5 DC from the speaker. | Positive lead faces LM386 pin 5. |
| 1 | Supply capacitor | 100 uF, 16 V electrolytic | Supports low-frequency current near the IC. | Positive to pin 6 rail, negative to ground. |
| 1 | Supply bypass capacitor | 100 nF ceramic | Stops fast supply noise and oscillation. | Place directly between pins 6 and 4. |
| 1 each | Zobel network | 10 ohm resistor in series with 47 nF capacitor | Stabilises the output with a real speaker load. | Series pair from pin 5/output node to ground. |
| 1 | Speaker | 8 ohm, 0.5 W or greater | Turns the amplified signal into sound. | DC resistance usually reads about 6-8 ohms. |
| 1 | Battery, clip, and audio socket | 6-9 V battery supply; 3.5 mm mono/stereo socket | Supplies safe power and a repeatable input. | Tie stereo L/R through resistors if combining them; never hard-short them together. |
Build boundary
This is a small battery-powered learning amplifier. It is not a guide for valve/tube amplifiers, mains-powered supplies, car audio, or high-power speaker systems.
Part modules vary. Read the markings and datasheet for the exact board in front of you before applying power.