Reaching out to the folks who really understand sound and who might also be electricians :)

We have a pretty solid sound system at my church but I think the electrical work in our room is not so great. Our worship room is an older part of the church built in the 70's. The sound system was installed a few years before I started working there but with the issues we're having I have a feeling that the electrical work in the room HAS to be the original wiring.

I can't plug in a tube amp on the stage and run it anything but clean without there being an obnoxiously loud buzz. Even the clean channel has a buzz, though it is slightly less obnoxious. I can take the same amp into another room in the church or in another building all together, crank the gain and play metal riffs and only deal with a small amount of hiss that comes from a cranked high gain amp. I've experienced this with multiple amps loa array. If I run any drive on the amp or from pedals in our worship room I have to use a noise gate. I also use a Furman power conditioner for the guitar amps.
http://amthanhthudo.com/loa-line-array
I've also noticed that just plugging things into outlets on the stage can cause a buzz at times on the stage as well. I can plug in something to an outlet that isn't even plugged into the sound system and there can be a buzz.

I know next to nothing about electrical work but it seems like we've maybe got a grounding issue? We may need all new electrical work in that room.

I guess my question is - anyone else meet in an older building and deal with similar issues? If so, what do you do? I hope all of this is making sense.

Thanks everyone!