Slight hum in my amp. Is this normal?

I tried a different power cord. If it were a ground issue, wouldn’t running it through a power conditioner such as the Torus correct it? Also, the Torus is plugged into the outlet by the left channel and I tried plugging directly to the outlet by the right channel. And the electrical connection is a two wire AC connection to the power source.

After all this, my problem isn't a ground loop, bad ground, or anything external. Reading my email to the repair shop will explain;
Hi Morris,
Ok, I’ve exhausted my resources and have isolated the problem. I have a dedicated AC line I tapped from that powers my tankless water heater. This is a new line installed about 4 weeks ago and the water heater is the only thing powered by it so I ran an extension cord to the Anthem. The only connection after the Anthem is speakers. No input connections what so ever. The “hum” is in the amp AND audible through the speakers, all 5 channels.
I still have my Integra DTR 50.3 and for giggles, unboxed it and connected it. Again, AC line into the Integra and speaker wires to the corresponding speaker. Result, DEAD QUIET! I went a step further and connected the Integra to the wall (not the dedicated line), same result. Another step further and connected the AC line to the Torus, Torus to the Integra, Oppo BDP-103 Blue Ray to the Integra, speakers connected. Again, DEAD QUIET!!
My comparison is a $700.00 Integra AVR to a $4,000.00 Anthem amplifier.
Conclusion; there is something going on internal to the Anthem. No question about it. It’s something common to all 5 channels.
Lets review the chain of events….
When I lived in my condo, you serviced the Anthem and it worked beautifully! Had there been a “buzz”, I would have noticed. I’m POSITIVE of this!
I moved to this house and upon installation, I found the Surround Right channel dead, so I brought it to you. Then technicians finding was everything was good. Considering the contradiction, you recommended the technician disassemble and reassemble the amp.
Up to this time, I never heard a “hum” from the amp. Again, I would have noticed it.
As soon as I got it home, connected everything, I heard the “hum” immediately and brought it back. You called me and said there were no problems and I took a leap of faith doubting my own observations. I’ve never heard a “hum” from an amp before. You stated all amps have a little bit of noise if you put your ear close enough. I wondered why I could hear it from my seating position. Were my ears that good? Possibly but, thats when I put my ear close to each and every speaker and discovered the same “hum” from the amp, I heard coming from each and every speaker.
This is when I brought it back to your shop. In addition to the “hum”, the right side front panel ear was loose which got fixed.
Immediately when I put it back in the system, the “hum” was apparent and I tried to describe it best I could. Again, doubting my own judgement, I gave it a day or so. I came to the realization that what I was hearing was not normal.
It all became real to me today when I put the Integra in the system! To add icing on the cake, the technician neglected to install one of the housing screws and your office lady, had to mail it to me. It arrived today and I installed it.
Morris, I’m at a loss on what to do at this point. It’s clear the amp is not functioning properly. A piece of gear of this caliber should be light years better than the Integra it replaced in my system, and it was, until the technician disassembled and re assembled its innards.
I need to know how we are going to address this. I’m very upset and exhausted at this point and ready to send it to Anthem in Canada. Before I do, I need to know what you can offer for a solution. I know this will get resolved, the question being by who and at what cost. I’ve thrown a lot of $$ at this already.
Thank you and I look forward to resolving this expeditiously.

Not likely to be DC on the line, but if you think it is, I have a PS Audio Humbuster I can sell you which did not solve my problem. For toroidial transformers, the mounting position is sensitive to hum, try rotating the right tranny around its axis for minimum hum, and the tightest position of the mounting nut may not be minimum hum. You can also order polymer washers from Herbies to better damp the hum, If the Anthem is 15 years old, it may also be the filter caps which may need to be replaced.

For those who have offered advice, education, and information, I am very thankful. I've tried everything almost imaginable to find the source of the "hum". I've deduced the problem to it's source being my original assumption. Doubting myself provided a lot of experience and I'm sure useful education for myself or someone else one day. I decided to send the amp to the factory where the technicians who will repair my amp work on only one brand, the one they specialize in, their own!

The shop did not reply to my email. I became more upset by the hour and decided to send it back to its creator who will surely find and fix the problem. Stay tuned as I will surely post again when my Anthem amp returns and is functional again.

Lesson to learn here; don't take a Ferrari to a Chevy mechanic!