jazzuar – Having a studio above a power intensive business just seems like an invitation for “issues”. It sounds like what you need to address the grounding issue is a power conditioner. It is not stompbox related as there seems to be a grounding issue within the building’s wiring – based on what you’ve said. I suggest contacting an electrical contractor and see if you can “try out” a power conditioner. If a power conditioner does not solve the grounding issue(s), then you have some real troubleshooting work in front of you to resolve grounding on each and every amp you have. If you cannot identify the root cause, it will be only a stroke of luck to solve it.