I never thought that ground loops could manifest themselves in that way.

Ha. Of course they can. Get this. Do you know what "Skywalker Sound" is? It's the audio post-production facility owned by Lucasfilm. They do a LOT of very high-dollar work for the film industry, lots of movies are mixed down there.

Last year, they spent a gazillion dollars re-working the grounding in the entire building. From what I heard, they tore up all the floors and installed basically a giant copper "net" under the flooring and tied every ground in the building to it. That net is connected to a super-duper high-grade made-for-NASA grounding rod. The engineers say the difference it made in their equipment noise is like night and day.

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Tony Fabris