A/C noise

I recently aquired a levinson 38 and upon powering it up I can hear a/c noise which is not prevalent in my other pre-amps...my question is: 1.is this normal for this make/model 2.is this a ground loop problem or 3. does it have a bad cap? It is on a dedicated circuit but is running through a monster hts5100.Thanks.
How loud is the noise and how close do you have to get your ear to hear it?
Lakefrontroad wants to know if it is more or less than 900 ft.
900 feet???!!! It sounds like an old adcom amp when powered up...slow hummmm 3-4 feet away. I cannot detect it when music is being played but I know it's there.