Have you ever felt if someone pulled or pushed your head when a specific device is powered on? Or felt increased blood pressure in your head and lost the ability to fully concentrate while a given device was operating?

I’m in definitely in this camp, and talked to several people who experience all kinds of discomfort when a given device is operating. While others are completely immune to this.

I did several measurements in the past as I suspected that it was caused by the electromagnetic field of the power supply or radio frequency radiation emitted by it. And haven’t found any correlation.

But while building my synth corner, I came across three Walrus Audio power bricks (one shipped with a Canvas Power 5 and the others belonging to Canvas Power HP+ units) that caused an extreme level of discomfort and annoyance, so I continued the investigation.

This time with a measurement microphone. My jaws literally dropped when I saw this on the spectrum at the instant the unit was powered on:

Walrus Audio Canvas Power bricks squeal all over the ultrasonic spectrum.

Those peaks are 30 dB over the floor, contaminating the entire ultrasonic spectrum.

As a cross-check, I did generate a 21.5 kHz test tone, and my reaction was identical to the noise coming from the power supply. Case closed for me. And I’m not surprised that so much effort goes into ultrasonic weapons research.

I understand that switching power supplies are operating at high frequencies, but that isn’t an excuse for sloppy design like this. The majority of power supply manufacturers can handle it properly.

So my standard test procedure for any new device now includes an ultrasonic contamination measurement – which already caught a handful of other problematic power bricks. But unlike the Canvas Power, these all were cheap power supplies included with synths and pedals.