Here, we present a powerful audio amplifier which is based on the popular LM3886. The circuit schematic was derived from device’s datasheet and we have built a small printed circuit board to make things easy.
LM3886 amplifier became popular because of the ease of use, it’s high output power, it’s low distortion, and it’s built-in protection against shorts and thermal runaway. There isn't much more to ask of a power amp IC. Just build and enjoy….
This amplifier circuit is capable of delivering about 65W of continuous average power to a 4 Ohm load and about 35W into 8 Ohm with 0.1% THD+N from 20Hz–20kHz.
Building the amplifier
Here, we provide a printed circuit board for a monophonic amplifier. If you wish to have a stereo version, you must build two identical mono-circuits (one for each audio channel). The required resistors are 1/4W type, except for R4 which should withstand about 5W. For a stereo amplifier it is better to use low tolerance, 1% resistors.
The LM3886 needs a large enough heat sink at a level such that the thermal protection circuitry does not operate under normal circumstances. The heat sink should be chosen to dissipate the maximum IC power for the given supply voltage and the rated load (for more details consider LM3886- datasheet). An inadequate heat sinking will cause thermal shutdown circuitry to operate and will limit the output power.
There is also another crucial aspect; the LM3886T package is not electrical isolated. The heat sink will be at V- potential when the LM3886 is directly mounted to the heat sink. Use a mica washer in addition to thermal compound, if you wish the heat sink to be isolated from V-.
Powering the amplifier
The circuit can be powered from a relative simple symmetrical power supply unit of ±28 -35V. The power supply unit should be able to provide more than 100W under extreme conditions. A 2x25V transformer, a rectifying bridge and some filtering capacitors are enough to power up the amplifier.
65W audio Amplifier, PCB Layout
Artwork by A.G