You are right, a 20K Hz signal won’t be heard except maybe by grandchildren, but it will affect plug-ins attempting to analyze and process sound.

I just looked up and discovered 50 Hz is your power frequency in Australia. It’s 60 Hz in the US. That doesn’t change any of my answers.

The tester I use now is a $20 tester at Home Depot made by Klein Tools. It has a text readout in addition to the light pattern found on the $7 version that used to be all that was available. I have no idea if the one sold here for 60 Hz works in Australia but check Klein Tools. I carry a tester in every gear bag and won’t plug in any gear to an outlet before testing it first.


BIAB 2024 Win Audiophile. Software: Studio One 6.5 Pro, Swam horns, Acoustica-7, Notion 6; Win 11 Home. Hardware: Intel i9, 32 Gb; Roland Integra-7, Presonus Studio 192, Presonus Faderport 8, Royer 121, Adam Sub8 & Neumann 120 monitors