Nelson's PSU Filter Relay Essentials 2022

"About a year and a half ago I released a power supply filter board and thump suppression relay circuit to go with the DIY Sony N channel VFET amplifier kit. The P channel version did not particularly need this, as the VFET Drain was grounded and so not exposed to the noise of the switching power supply V+. In the case of the N channel version, the supply noise leaked through the VFET by virtue of its low Drain-to-Source impedance, and further, it displayed much larger turn-on and turn-off thumps.

However the relay action on this circuit was not good enough to prevent thumps on turn-on and turn-off, and while it limited the thump still caused complaint. This supply filter and relay are designed to do the job with more finesse. It is useful for single supply amplifiers and line level circuits."

- Nelson Pass