question for Luxman L-590AX owners

I own the subject amp, have had it for 3-4 years. I recently noticed a low hum or buzz coming from the amp itself (not the speakers), and would swear that it has been dead quiet up until now. You have to have your head right down beside it to hear it. I'd like to hear what other owners have to say. Are your amps completely quiet? Seems like I may have developed an issue. Thanks in advance, and Merry Christmas.

builder312-25-2020 1:48am

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imhififan Details Discussions Posts This discussion Message User 2,181 posts 02-01-2021 at 09:01pm Copy Comment URL Report Comment Edit Delete @twoleftears The power transformer in the Luxman is a EI type and not a toroidal transformer. https://6moons.com/audioreviews/luxman4/6.jpg
twoleftears Details Discussions Posts This discussion Message User 5,318 posts 02-01-2021 at 10:17pm Copy Comment URL Report Comment Edit Delete 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 Details Discussions Posts This discussion Message User 2,181 posts 02-01-2021 at 11:45pm Copy Comment URL Report Comment Edit Delete Yes, some toroidal transformer cores consist of a very long and thin metal strip that is wound up (like a spring) in a large circle rather than exist of lots of individual metal parts. A cross-section of the core: https://diyaudioheaven.files.wordpress.com/2013/08/o-cores.png