Audio Research LS2SE tube buzzing

For some time and after using multiple set of tubes I have noticed that my Audio Research LS28SE pre-amp has a slight buzzing noise from the tube area of the pre-amp.  There is no noise through the speakers.    The buzz sounds like a transformer buzzing and I only hear it only when I am hovering over my gear like when my ear is a foot or so away.   It definitely  comes from the area where the tubes are and not the transformer.   Just wondering if this is normal for tube gear? It doesn't cause any issues from my listening position. 


Shouldn’t be buzzing. Have you tried swapping the tubes to move this tube to another socket in a preamp and see if the buzzing follows it?

No noise should be created. You have had multiple tube sets? Swap single tubes one at a time from a spare set until it disappears. 

I swapped all of the tubes with a known good set and have the same issue. At some point I’ll drop it off at Audio Research to check as they are local to me. Since I can’t hear it from my listening spot I am in no rush. Thanks for the tips everyone.