Do all toroidal transformers hum?

Thank you Stanwal and Tbg, that was informative. The funny thing is that I had Denon POA 2400 (200W/channel) not a sign of hum, but the DK does have a faint hum. I guess I have to live with it as it's not audible 3 inches away from the amp. The Denon had a cheap 2-pront (no earth) power cable, do you think the grounding might be an issue? I had a B&K MC 101 Pre-amp with a IEC power cable and that had a hum too.

I had significant hum problems with my Karan K180 amp. Much to my suprise, changing the power cable made a big difference, not sure why, might be worth a try.

How did you get from "can't hear any hum more than four inches away"... to.... "All toroids are inferior?".

If you aren't wearing the amps as headphones the hum issue should pose no significant issues.

Certainly, if you have toroids in your amps and don't like your amps... perhaps only those toroids in your own amps are inferior.

Relax. Don't sweat the petty stuff, but do remember to pet the sweaty stuff now and then.

Stan outlined it pretty well already.

The reason for the hum is what is called magnetostriction. You can read about it here.

It may also be sensitive to the tightness of the transformer mounting screws, and to the design of the mounting arrangement, which might influence the degree to which the vibrations are amplified or damped by the surrounding structure.

Regards,
-- Al