question for Luxman L-590AX owners

Reports of Luxmans with hums go back at least five years, probably further.
https://forum.audiogon.com/discussions/luxman-class-a-integrated-slight-buzzing-noise/post?highlight=luxman%2Bhum&postid=78228#78228

@builder3    Can we go back to basics?  Would I be right in assuming that you've had other integrated amps or power amps in the same house that, when plugged in, didn't hum?

We also have reports of exactly the same model humming in other people's houses, and also occasionally examples of the same model with no hum.

From this I conclude that it's either:
-an interaction of the design of the amp with the power supply; some feature of the design makes it susceptible to hum in many but not all situations;
-a QC issue of many (but not all) examples of the transformer used in that model.

Noted.

One can see the laminations quite clearly here on a stock E-I model.
https://www.ec21.com/product-details/EI-Transformer-Lamination-Magnetic-Core--10623566.html

I’m still curious about the construction of toroidal cores.  Are they built up with very thin "doughnuts" of laminated steel stacked on top of each other?

@imhififan This is fascinating.  So is a toroidal core like a spool of one continuous sheet wrapped around itself, or is it built up of an accretion of concentric circular sheets, each one slightly larger in diameter than the previous?