Amplifier hum - normal?

I have owned several SS amps.

Bryston 4B SST - no hum whatsoever
Bryston 14B SST - no hum whatsoever
McCormack DNA-2 - no hum whatsoever
Odyssey Stratos Mono Extreme - no hum whatsoever
Belles 350A Reference - no hum whatsoever
Belles 150A Reference - hummed like a $10 hooker
Pass Labs XA-60.5 - no hum whatsoever

My history with SS amps suggests that no hum is more common than hum.

I too have owned a good number of high powered solid state amps and never had any hum issues. I have had hum problems with large toroid isolation transformers. A lot of modern amps have toroids, which are more prone to humming and buzzing as a result of DC on the power line. I would look to exclude this as a possible source of mechanical hum.

All transformers will hum a little but only poorly constructed ones will generate excessive hums. I would consider that a defect if you can hear it more than a few inches away, especially in a modern high-end amp. The propose of a high-end amp is play music in a quiet room. It shouldn't hum at all.

Hmm... I'm not sure what would constitute excessive or normal. I have sensative ears... lol, but I'm sure we all do here.

Idk.

"A lot of modern amps have toroids, which are more prone to humming and buzzing as a result of DC on the power line."

As far as I know Toroid is very quiet compare to non-toroidal transformer. In addition is more efficient because of low stray magnetic field (one tenth of traditional transformer) and higher power rating for the size because of higher flux densities (up to 18000 Gaus vs 14000 Gaus in non-toroidal transformer).

The only disadvantage of toroidal transformers that I know of is cost of winding.