You don't think the mechanical hum is likely to be the transformer? A DC blocker may help or it or may not. I have similar hum in one of my amps and a DC blocker did not help. Others have said that a DC blocker fixed this problem.That way a lot of obvious voodoo bullshit lies; and - as far as I can tell - very little that's convincingly not bullshit...
Edit: maybe you will still think this is all BS but here you go anyway
https://www.audioholics.com/amplifier-reviews/monoprice-monolith-7-channel-amplifier-review
If you have dimmers in your house or the issue known as DC offset then the Monolith’s massive transformers may start to hum. They did in my case when the lights on my microwave were on and set to low. To be clear, this isn’t a design problem with the Monolith. To fix the humming, I plugged the Monolith into Emotiva’s CM2 AC line restoration and common mode filter system. This two-outlet receptacle is specially designed to eliminate DC offset issues without limiting current or dynamics.
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