Hi all,
My Zesto amp is pretty new - a couple of years old. The hum was there from the start, but my previous speakers didn't emphasize it as much as my new speakers do. As a few folks have said, the efficiency of horn speakers has a down side.
The sound comes out of the speakers, AND if you put your ear to toe back left of the amp (where the toroidal transformer is), you can hear it buzzing there, too.
I like (well, at least as a path) the notion of unplugging many things in the house - I've already done so in the listening room itself. My listening room was a "found" space - it was an old three sided porch on the side of the house I enclosed and made into my room. It lives on top of the boiler room in the basement. That room has an oil burner (with a pump for the oil), and since it is baseboard hot water heat, it has multiple pumps to circulate the heated water throughout the house. I wonder if those pumps are throwing junk into the line?
Anyway, you have inspired me to search for the equivalent of the coffee maker that a poster found in his house. The source is out there...