80W Power Amplifier

I bought an AV receiver with a built-in subwoofer amplifier that can drive the subwoofer directly. But, the output power is too low. I then designed this simple boost amplifier.

The heart of the amplifier is the LM12C which only needs a few external parts. The 4u inductor is a custom part. I wound 10 turns on the 2.2 ohm 3W resistor with 20AWG magnet wire. The input transformer is a small AC adaptor which can isolate this amplifier from the AV receiver and, at the same time, provide 10X voltage gain. See the picture below.

The input transformer

The LM12C is installed on an heatsink. All parts (except the input transformer) can be put into a standard PC power supply case.

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End of the project

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