Nord Stage 4 - Audible buzz from power supply area

[Bonitoman]

I bought a Nord Stage 4 88 (v2.21 Rev.B) two weeks ago and returned it because of the annoying noise from the power supply or transformer.
Today, I bought a new Nord Stage 4 88 (v.2.23 Rev.B) from another supplier. Unfortunately, the noise from the power supply or transformer is still audible on this device.

Does anyone have any idea how to make it quiet?

This is the first time I have purchased a Nord device. According to previous forum posts, this problem seems to have been known for years. I find it incomprehensible why this problem has not yet been satisfactorily solved. Other brands have no problem installing silent power supplies.