Slight hum in my amp. Is this normal?

What jea48 said.  I just didn't want to be an accomplice if you touched the wrong place with your screwdriver.  Let us know what the solution was.

Today I dropped it off at the local authorized service center who has been the only company to work on my amp. Interesting thing, without opening the cover, I put my ear real close to the vents adjacent to the transformers, there are two, one on the left and one on the right just behind the front panel. I could swear the hum sounds slightly louder from the right side making the right side transformer suspect. I used an analog decibel meter using fast and slow response, and it's hard to tell with the slightest ambient sound pressure. It measured approximately 55 dB with the right side maybe 1/2 - 1 dB higher. Are my ears that good? the proof will be in the pudden when the shop gets into it. The owner said he would get in early when it's dead quiet and listen for the hum.
I told him today that the hum is loudest when power is initially applied then quiets down however, I can still hear the hum from 10 ft away when the room is quiet. Of course when a program is playing, the speakers drown it out so It's inaudible. My Integra DTR-50.3 AVR, $700.00 retail has always been dead quiet. Certainly a $4000.00 retail Anthem A5 amp should be as well.
Lets see what they say in a couple days. Stay tuned!

Wow, I thought it was bad hearing hum from my Klipsch speakers from 12 feet. I'd be pissed if I could hear the actual transformers! I have an Emotive  CMX-2 ($127 w/tax) coming tomorrow. I'll report on its efficacy.

Wow, I thought it was bad hearing hum from my Klipsch speakers from 12 feet. I'd be pissed if I could hear the actual transformers! I have an Emotive CMX-2 ($127 w/tax) coming tomorrow. I'll report on its efficacy.

If the cause of the hum is DC on the line, it certainly should work. It can't hurt in any case, unless one considers the two blue status indicators to be "active" and thus draw some minuscule amount of current.

You can have DC on the line and oddly enough, it can be passed through transformers. It could also be considered a 2nd harmonic as basically its caused by loading on 1/2 of the AC line and so the AC waveform can be offset slightly just as if it were riding on a slight amount of DC. The resulting asymmetry could be interpreted as a 2nd harmonic.

Its easy to correct with a DC blocker which is a simple and inexpensive device. DC on the line can cause the core of the transformer to saturate, causing it to rattle or hum. It can vary from one transformer to the next even with parts from the same construction run.

Grounding in the house has nothing to do with this problem even if its not DC on the line. So the age of the wiring isn’t the problem.

Transformers can be mechanically noisy on their own despite the best of intentions. Tightening a noisy part down won’t help and might make it worse. But sometime the part is causing something else in the chassis (like a cover) to resonate and it might be possible to damp that part. If you can only hear the problem when you are within 6 inches of the amp its not a problem. IME, most audiophiles listen to their gear considerably further from the amp they are playing :)

Getting quiet transformers is always an on-going challenge. Transformer manufacturers often don’t understand how important it is for the part to be silent and might sometimes skimp on a few core laminations or the like thinking they can save a buck. In the process they might loose the entire run as reject parts!

Good Luck!