where is this transformer? (I mean in you studio) Masive transformer equals massive hum if you're close to it...tbh I would like you to send (email) about ten seconds of the hum if you can...laugh if you will my record of doing this is pretty good...different types of hum can tell a lot about what's up, and often it's something that's very simple...when I read about your speakers humming too, that sounds like it could be inteference as opposed to grounding....I've got a massive 5KVA transformer that I hope will do the job, then it should be guitar heaven.
