FYI, the following is cross posted to two list serves.
A mysterious squeal appeared in the transfer chain here in the audio lab about two months ago. It's a tone centered around 10,330 hz and seems to be coming in on the AC power lines for a good portion of the building. This has been determined by taking a piece of equipment (in this case a Soundesign 8 track deck with integrated amplifier and a pair of headphones) and plugging into several outlets in the building. The tech power outlets for the recording studios are clean as well as some outlets on the 2nd floor but many of the 1st floor outlets have the offending tone present.
I've tried isolation transformers and low cost IsoBar type line conditioners with absolutely no luck. The tone appeared at approximately the same time of a revamping of the air conditioning system for the building and stringing of lines for some sort of digital cable. One of the campus electricians did some switching around of breakers and various things but nothing has helped. Before I go out and get a high end line conditioner to try out I thought I'd tap the collective wisdom of two of the best informed list serves. Any ideas?? I'm sure I've not provided the best description in the world so I'll try to answer any questions that arise.