Friday, June 24, 2011

3W- 5W Audio Amplifier Circuit

The following diagram is the class-a audio amplifier circuit. The circuit capable to deliver about 3W up to 5W power audio output.

Schematic diagram
3W- 5W Audio Amplifier Circuit diagram

Parts List:
R1 = 100K - 1/4W
R2 = 12K - 1/4W
R3 = 47K - 1/4W
R4 = 8K2 - 1/4W
R5 = 1K5 - 1/4W
R6 = 2K7 - 1/4W
R7,R9 = 100R - 1/4W
R8 = 560R - 1/2W
R10 = 1R - 1/2W
P1 = 47K Log. Potentiometer
C1,C2 = 10µF/63V
C3 = 47µF/25V
C4 = 100µF/35V
C5 = 150nF
C6,C7 = 220µF/25V
C8 = 1000µF/25V
Q1 = BC560C
Q2,Q3 = BD439

Circuit Notes:
  • Total electric current drawing of the circuit, recommended measured by inserting the probes of an multimeter across the positive output with the power supply and also the positive rail input with the amplifier, should be 700mA. Adjust R8 to obtain this value if needed.
  • Q2 and Q3 must be mounted on a finned heatsink of 120x50x25mm. minimum dimensions.
  • If needed, R2 could be modified to get 13V across C8 positive lead and negative ground.
  • Add R5 and C5 if the bass-boost facility is needed.

3W- 5W Audio Amplifier circuit source:

About Audio Amplifier
An audio amplifier is an electronic amplifier that amplifies low-power audio signals (signals composed primarily of frequencies between 20 - 20 000 Hz, the human range of hearing) to a level suitable for driving loudspeakers and is the final stage in a typical audio playback chain.

The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification, equalization, tone control, mixing/effects, or audio sources like record players, CD players, and cassette players. Most audio amplifiers require these low-level inputs to adhere to line levels.

While the input signal to an audio amplifier may measure only a few hundred microwatts, its output may be tens, hundreds, or thousands of watts. More explanation about power audio amplifier can be found at

This is a video tutorial about how to a very simple audio amplifier based on the LM386 amplifier chip. It can be built for less than $20 (or might be less than $8 in some countries) and used to amplify any low level audio signal including a guitar, bass or mp3 player.

Watch the video:

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