Slight hum in my amp. Is this normal?

I have an Anthem A5 and when I turn it on there is a slight "hum" if you put your ear close to it. From 3 feet away it’s unnoticeable. It's in the amp, not in the speakers.
Is this normal?
Thanks, Ralph. To be clear, though, am I correct in believing that to the extent the asymmetry of the waveform corresponds to a 2nd harmonic component, neither a DC blocker nor a transformer would eliminate it?

Best regards,
-- Al

^^ Yes- and that is what we are dealing with when the power transformer in most audio equipment is involved. Its best to block the DC prior to a transformer- otherwise you have to use a very sophisticated power conditioner!
Is your system set up for pure stereo?  Or, are you connected to some video theatre stuff too?

If so....disconnect all the inputs from sources leaving only one source at a, phono...etc.

I'm thinking you need to rule out groundloop.

I had the same problem to my Constellation Mono amp.  Amp checked and find nothing at the Constellation repairing center.  Checked with Shunyata Research, I used quite a lot electrical products from them, they said probably a DC on the main.  With a reasonable low cost for a try, I tailor-made 2 DC blockers (one for each channel), to which to ensure sufficient current serving the Mono amp.   No hum from amp anymore, and more importantly that would not affect the sonic performance. 
My amp has been at the shop since Wednesday and the owner called me this morning at 7:00 am when the shop was dead quiet. Said he did agree the transformer on the right was a bit louder than the left however it was a normal hum. I explained again that it was loudest when you first power it up then the hum diminishes after a few seconds but is still audible. He wants to keep power applied to it and observe.
Another thing I just remembered and haven't mentioned, since the hum began, it has been running a bit warm even at low listening levels when it was in my system. Another thing is this whole thing only began when I moved into this house with knob & wire electrical. It is on a 20 amp circuit.
All of these things suggest DC in the line. Just to review; all of the problems began when I moved in this house. First thing was the surround right channel was dead. The shop found no malfunction indicating a loose connection that suddenly worked when I delivered it to the shop. As a precautionary measure, they disassembled it reseated everything. When I brought it home is when I noticed the hum. After bringing it back to the shop, being told it was normal, brought it home and noticed it running warmer than normal and of course the hum was still there. Since I refuse to accept that its operating normally, its back to the shop.
Again with everything I've read, this smells of DC. Even a Torus TOT MAX made no difference. I just ordered an Emotiva CMX-2. I plan to call the shop tomorrow for status.
Anyone care to guess what the problem is?
My guess is; 1- there's a bad connection, 2- a faulty component (transformer), or 3- DC in the line.