Toroidal transformer hum

I had the same problem in my last aprtment. Fixed it with a ps audio humbuster. Think I saw one fr sale here recently. But if you buy from ps audio or the similar product from channel islands audio then you will get a 30 day trial period. If it isn't dc on te line, just send it back. Don't recall if there were restocking fees or not.

I had the same problem with my Quicksilver amps.
When I called them they told me if I have them on a shelf to put a carpet under amps and that did fix the problem. It was a vibration causing the hum. Give that a try if it works then you can get something better like a set of isoblocks [cork block] and put them under the feet of your amps!

The amp is sitting on the very bottom shelf which is glass.

That might be the problem.

There is no way that one should be able to here a transformer from 13' away, especially a toroid. Yogiboy may be correct about the shelf agrivating it, but I would assume that the previous posts about DC are along the lines. If you can borrow an isolation transformer, that would be my first thought.