Worth checking if it's responding to DC on the line. Turn off everything else in the home, via breakers, and see if it goes away. :)
Even if it is DC, it's not harmful, and the only negative effects are your level of annoyance.
Problem is not the wiring, have a Macintosh 6100 here also, that is dead quiet even if you put your ear right to the cabinet.
Its the 250 transformer Im sure and annoying as heck.
I have it in my bedroom and like listening at low levels through the night. I can hear this at over 12' away.
The dealer gave it a 30 day warranty, sadly to say its going back. Its a beautiful example but ...
Back to the Dc blockers, its not the AC here. I have other receivers and and some tube stuff and nothing make a hum like this.
House was rewired less then 8 years ago.
This amp would be great for a loud environment but not good for my application , plus these products are supposed to be quiet. So there is something going on and perhaps on the way out.
I did check to see if the mounts were loose and nope that was not the issue.
Its either the transformer going or something else causing the transformer to act up but at this point itys under warranty and Im not screwing with it anymore
Just wanted to clear this up. This was a Ebay purchased, seller dealer offered 30 day returns.
Dont care what transformer is in it or not ,nor about my ac here.
Have plenty of audio stuff here and have the common sence to know when something is not right and there is a issue.
Have been reading on this issue and it does happen for many different reasons.
Transformer being loose on the base, inside of the transformer loosening up and have read re- shellacking it, having it rebuilt or replaced, or something electronic wise is going south.
I did not buy this as a project , this was supposedy checked prior to the listing and the seller offered a 30 day return for faulty item.
Had they not been states away I would of ran it over and had them repair it if it was possible.
This is not the issue, there is someyhing wrong with it perood and its going back.
Its a beautiful piece but there is something wrong and for what I paid I would expect it to be working %100.
Thanks again for the thoughts and again consider this issue closed.
Another solution is do to what this guy did
https://forum.audiogon.com/discussions/dc-offset-blocker-killer-where-to-buy-in-the-usa where he whined that no one was willing to help him that McIntosh did not reach out to help him that contributors, posters, and users of this forum did not help him and so he was prepared to do nothing but decide to burn his amplifier because it was his right to do so it was under warantee but he was not willing to pay the shipping cost to return it to the factory!
Fyi I never had buzzing sound.
Its a annoying hum, I live in a nice area in Chicago, its all residential homes no commercial close by.
Com Ed ran new lines not too long ago and as mentioned our home has fresh wiring from the pole in.
Have, 3 pc here, many tvs as well as audio equipment.
If there was strange stuff going on with the power Im shure as shixx something else would of acted up by now.
Just my 2cents, Im done