10W Stereo Audio Amplifier with Transistors

This is another simple to build audio amplifier using common parts and medium power transistors. It outputs 10 W into 4 ohms speakers on each channel when it is fed with a 0.5 V peak-to-peak signal.

It is powered from 24 ± 1 V and has an input impedance greater than 100 k.

The output transistors must be able to handle 2 A of collector current and dissipate at least 20 W. Something like BD237 & BD238 or BD 437 & BD 438 pairs will do. The rest are general purpose transistors such as BC547, BC171, 2N2222, S8050, 2N3904 and their complementary BC557, BC177, 2N2907, S8550, 2N3906. The drivers of the power transistors, just like them, must be complementary and with similar current gain. So, if you have a hFE meter, do test the transistors and match them based on their hFE. If you can't measure them, follow the hFE markings. Do not match a BC547B with a BC557C because they have different gains.

Built amplifier (single channel, without heatsink)

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