Brigadoon - An Occasional Corner on the Internet
For any project that outputs an audio signal, such as the audio output from the Raspberry Pi or other microprocessor, the level is normally not high enough to produce a significant volume.

To boost the audio output to make it suitable to drive speakers, a small audio amplifier is often required. The XH-M177 amplifier shown is a stereo amplifier with inbuilt volume  control, capable of an output of 3W, 10% Total Harmonic Distortion (THD) using a +5V supply and 4 ohm speakers.
Audio Amplifier
Designed by Mark Little
The XH-M177 uses the PAM8403 amplifier which is a Class-D audio amplifier with up to 90% efficiency, using 8 ohm speakers. If the THD is kept down to 1%, the amplifier can provide 2.5W with 4 ohm speakers and 1.4W with 8 ohm speakers. This should be enough for a local audio output. The frequency response of the amplifier is adequate for music in the range 20Hz to 20kHz, subject to the frequency response of the speakers connected to the amplifier.


No mounting points are provided on the amplifier circuit board. It is assumed that the hole for the potentiometer and its lock nut provide enough mounting for the entire amplifier. Best practice means that the wires to and from the circuit board should be supported to ensure that they do not place a strain on the amplifier Printed Circuit Board (PCB).

All projects on this site requiring audio amplification with an output power of less than 2W will use these amplifiers.


This amplifier is not suitable for headphone application because both lines to the speaker are active and headphones normally use a common return line for the left and right speakers.