Back in March, 1977, Electronics Today International (ETI) released a project called ETI-480. This was a 50W and 100W power amplifier that was sold as a kit for nearly 30 years at places like Jaycar Electronics and Dick Smith Electronics. With this project, they showed a power supply for it, which included a muting (speaker de-thump) relay, to provide a short turn-on delay before connecting the speaker(s).

In this project, I have taken their original power supply design and modified it. Featuring 10,000uF capacitor bulk-filtering, the high current supply rail, separate ground connection for star earthing and a protection flyback diode on the relay.

Note: This is designed for use with a single amplifier as the relay specified is a SPDT, you would need two modules for stereo. There is also no +/-15VDC rails, however, there is a "DC" connector, which is the same as the "VCC" connection, but this allows it to be connected to a preamp that already has regulators built-in on it.

This was mostly designed for use as a guitar amplifier power supply unit, hence the single channel muting.

Here is a link to my YouTube video on this project: