Mechanical buzz coming from the chassis

May be that a bolt on the toroid is loose and needs to be tightened. Or could be DC on the line. If it is DC on the line, you can get a PS Audio Humbuster or an equivalent from Channel Islands Audio. The Humbuster fixed my prob in my last apt. 30 day trial for both products, so if DC on the line isn't the prob then you can return the product with no worries.

Sounds like tha amp is acting normal during operation if you have to place your ear that close to hear transformer hum. If it still bothers do what newbee suggest and also placing the amps of something soft if on hard surface. Placing them on a rubber mat does help.

I checked the screws on the power transformer, they were loose. I tightned them and the hum is nearly gone. I really have to get my ear in close to hear it now.

Do I need to be concerned that there is an underlying problem with the transformer or incoming power? I have a dedicated 20amp line for the system so there is not much I can do to improve the power.

This is a matter of degree - so how close does your ear need to be to hear this ?

I had the same problem with my Quicksilvers. I called and was told if the amps were on a shelf I should put carpet underneath amps which solved the problem. I bought a set of isoblocks (cork blocks)and put them under the feet of the amps and they work great. I think that should have been mentioned in the owner's manual.