In my attic I have my train room. I am an O gauge modeler so it is all Lionel stuff from the 40's, 50's and 60's. (Yes, I will admit I have some new stuff like MTH, Williams etc.)
I also have stereo set up in my attic as well. The unfortunate thing is that I do not have a dedicated circuit for my attic stereo system. If you are familiar with model trans, lots of big transformers operating the equipment. Needless to say, lots of AC noise on my attic circuit. Note: The attic receptacles. are on a dedicated circuit.
My solution is the DigiBuss that Dave makes. All my transformers are plugged into the Digi. The stereo system is handled by a MiniBuss. So far no weird noises on the stereo system with the Digi blocking out the nasties.
So if you are into model railroading and want to keep your AC system clean from the transformer noise, the Digi is the way to go!