Transformer hum?

I have four different items in my system that use
transformers. Levinson 436 monoblocks, a Balanced
Power Technologies BP-3.5 AC Conditioner, an Anthem MCA-50 multichannel amplifier, and a
Monitor Audio FB210 Subwoofer. All of them are
emitting a low level hum except one of the Levinson
Monos. When I plug anything into the AC conditioner,
the hum gets a tiny bit louder. In the evening, with no music playing, I can hear the humming from my listening position. With music playing, the system sounds fantastic, but I've got to think it would sound better if I could get rid of this hum. It is driving me batty.

What have I got and how do I fix it?
You probably have noisy AC lines, which may be caused by light dimmers. Turn off everything in the house and see if goes away.

Do a search on "transformer hum" for more ideas.
Agree that it could be the power. I will add that the power could be coming in that way from the street. One sure way to solve it, if that is the problem, is to use an issolation transformer. Those power regenerator conditioners are similar.
Cheater plugs are for ground loop hums, which you hear through the speakers. Cheater plugs won't solve your problem if you have mechanical hum.

Your transformers are humming inside the gear correct (Mechanical hum)??
One term used to describe the cause of the hum is "DC Offset".

One potential pitfall of issolation transformers or regenerators, is while they will solve the system mechanical hum, it is possible they will hum themselves since they are getting the same bad power the gear was getting.
Cheater plugs are an adapter so a 3 prong AC plug can fit in a 2 prong socket (one without the ground). They cost about 50 cents each at any hardware store, Lowes, Home Depot, etc.

Audiophiles use them to "lift"/remove the AC ground from a component. They will work for "ground loop" hum, which is a low hum sound you will hear coming out of your speakers. They will NOT help at all with a mechanical transformer hum.
Today, I tried using cheater plugs, but it didn't help.
I've been plugging and unplugging, isolating, trying
different combos, etc. etc. Unless the cheater plugs
need time to work, need to burn in or something, I can say that cheater plugs are not the answer. I do not have dimmers on this circuit. I have tried disconnecting
the TV cable. Didn't help. I don't know if I have mechanical hum, or not. It seems like a weird coincidence that I have 5 items in my system that
use transformers and four of them hum. I have florescent lights on a completely different circuit and when they are on, the humming is much louder. But when I turn off all the lights in the house, I still hear
a light humming coming from my components.
To add another wrinkle, one of my Levinson 436's
hums, but the other is stone silent. I have heard that
a ground loop hum can be identified by whether or
not you can you can hear it in the speakers. I can
hear it in one speaker, but not the other.

I suspect the electrical system, but I don't know
enough about it to know if I am on the right track,
or not. I was hoping the AC conditioner would solve
all AC problems, but it seems susceptible to whatever
is affecting the other components. Or, coincidence or not, I have four components that just happen to have
mechanical hum.

Does this information help?

Take one of the devices to a friend's house that has good power and see if it hums there. If so your transformers may need attention. I suspect that these transformers make the noise even when in stand alone and not hooked to any other components.
It doesn't matter if the dimmer is on the same circuit. Everything is tied together back at the breaker box. The dimmer on the light in my stove hood upstairs made a balanced line conditioner hum in my basement. If you are in an apartment your neighbor may have a dimmer causing the problem. The fact that a flourescent light makes it worse confirms my suspicion that it is noise on the AC line.

Mechanical hum means the piece is vibrating i.e., the hum is not coming from the speakers. Cheater plugs will have no effect on this hum.

Have you tried turning off everything in the house yet?
Mechanical hum happens because the transformer is working a little harder to provide the correct current to the gear.

See if you can borrow an issolation transformer or one of those PS Audio power regenerators (or similar). These will provide the correct current to your gear, and will allow you to hear if the hum goes away.

The above are a solution to mechanical hum. Sometimes though the transformer in this piece of gear will hum a little because it is getting the outside power. Better one than all the gear. It can always be muffled away if this does happen.
Try taking the Anthem completely out of the system. They are notorious for ground loop problems.
>>Have you tried turning off everything in the house yet?<<

Yes. I even turned off the refrigerator. I have plugged
and unplugged, isolated, paired, tried with a component
plugged into the AC Conditioner tried with it plugged into the wall -- all different combos and one at a time. Still hums.

There is one dimmer switch on another circuit. But,
I had that light turned off. Could it cause a hum even
if it is turned off?

Man, I would love it if it were just a matter of replacing
a dimmer switch. On the other hand, I don't know how I
would explain to my wife that we can't have a dimmer in
the dining room. However, I could replace it just to
see if this is the cause -- at least I would have peace
of mind.
Sugar --

Thanks for the suggestion. I would eventually like
to have a few dedicated AC lines run so the amps can get plenty of AC. Why does the transformer hum if it is
working extra hard? Can you explain that further? Also, how does dirty AC make the transformer hum and why doesn't
the AC conditioner, BPT-3.5 -- eliminate the hum when
components are plugged into it?

Transformers work because the expanding and contracting magnetic fields in the primary windings created from the changing primary currents cut through the secondary windings and induce current flow.

Transformers are designed to operate with a pure sinusoidal waveform. The current swings very smoothly from positive to negative with no abrupt transitions. This means that the magnetic fields are also expanding and contracting very smoothly. If you were to apply a non-sinusoidal wave like a square wave to most power transformers they would hum loudly due to the violent transitions of the current and magnetic fields. Any deviation from a pure sine wave can potentially cause these transformers to hum.

A dimmer works by chopping off part of the AC cycle and this produces noise spikes which travel through the system, and when they get to the transformer they cause it to vibrate. Not as much as a square wave but the principle is the same.
To see if the dimmer switch is the cause, go to your AC panel and find the circuit that the dimmer is on and turn that circuit off. If the hum is gone--there is your problem--if not look elsewhere.