Running a wire may or may not help given that both outlets are persently grounded already. It would help if you float the outlet at one end and substitute the ground that you ran from the other end (your one ground reference). Running an extension cord is more certain.

If any of your equipment has a 2 wire plug, try reversing it. That is required for my sub to avoid hum.

But please remember that playing with AC wiring is a job for someone who knows what they are doing. Fooling with grounds and running AC wiring is not for the faint of heart -- unless you happen to have an electrician's licence! I'd hate to see an Outlaw cause a fire or cause a safety hazard rather than diagnose the problem and then call in someone to deal with the wiring.

I don't think I was clear and should clarify. I was talking about buying one of the adaptors made for doing just what I am suggesting. The ones that take a 3 prong plug on one side and 2 prongs and a green wire with a lug on the other end. The green wire is susposed to be connected to a ground. I was just suggesting getting that ground from across the room. Also, you should not plug anything in until all the grounds are securely connected.

I would strongly advise against opening the outlet box and fooling with the wires inside.

Thanks for the suggestions, I think I am going to extend the power cord from the ceiling to the outlet by the a/v gear. Getting both outlets to use the same ground requires me to run wire also, so I might as well make disconnecting power to the projector easier in the process...now just need to find a cheap source for a 12 ft cloverleaf power crd (like many laptops use), or a C5 to C13 adpater so I can use a regular computer power cord, and adapat it to the cloverleaf at the projector. A regular extension cord won't work beacuase the plug portion of the extension won't fit in the plastic cover used to conceal the cord.

All the grounds in your house wiring end on the same bus bar in your panel! The adaptors or "cheaters" have a green loop on them where you are supposed to screw the plate cover screw to ground them for a correct installation. If you kill the circuit you can pull the outlet out of the box and verify the ground wire is still connected. The other thig is to go into the electrical panel and carefully check and make sure the ground connections are tight. The panel ground is supposed to be wired to the water pipe, in older installations, and in newer installations the water pipe and a ground rod. Jim

So are you saying you think the buzz/hum might be because the ground on the outlet in the ceiling for the projector no longer has the ground wire connected, or that maybe even the panel in the fuse box for the circuit has the ground disconnected? I thought it was typical for people to have these problems when audio/video devices were connected via video/audio cables, and their power connections were not on the same circuit. If all the grounds are connected and all the circuits of the fuse box are connected to the same ground, is the problem still a "ground loop", or more because of using different wires to get to ground.

Ground Loops are tough to ferret out!!! As an electrician I'm letting you know where I'd start. I tseems to me in most cases ground loops are caused by interference placed on signal cables. I.d check the grounds as stated to eliminate the ground ware as the culprit. I've seen waires installed on the ground bar looking like they were placed correctly only to find out they were resting behind the ground bus!

I've also seen where it is a faulty piece of equipment injecting the noise on the signal wires. Jim

The $3 solution to check the outlet's ground: go to Lowes/HD and but one of the plug-sized circuit testers that plugs into the outlet and has three lights on it. If the lights that come on when you plug it in match the "open ground" diagram on the tester, you need to have an electrician check the ground connection.

What sluggo said.

About three years ago I solved the slight hum problem by properly grounding of my Comcast cable lead-in cable.