How’s this for procrastination? I’ve had these boards ready to sell since 2017, and have been using them in my own projects, but only now got them up in the store! Buy them here…
An earth-loop breaker works to reduce noise in a system, by inserting a buffering impedance between a device’s signal ground, and its earthed chassis, to reduce currents circulating between them.
The metal-oxide resistor provides the buffered impedance at low frequencies, and the polypropylene capacitor—in parallel—gives a low impedance at RF. A bi-directional diode clamp—also in parallel with the resistor and capacitor—does nothing in normal operation, as there is 0VDC across it. In case of a fault, such as a DC power rail coming in contact with the chassis, or AC power being shorted into the device’s signal ground, the voltage across the diodes will rise above 0.6V, it will clamp, and the fuse should blow.
Recommended reading: Rod Elliot has a terrific article on the subject of “Earthing your Hi-Fi” where he describes the use of earth-loop breaker circuits, and gives invaluable advice on the subject of making electrically safe, and quiet audio equipment.