When you look at your power cords, the side with the stripe or the ridge is the Neutral and goes into the taller of the two slots in your wall plug receptacle. That's the best place to start. Get everything lined up so all the plugs are same. Three prong plugs will automatically play this way. If that does not do it, look for a place where you can use an optical link between components. That will break the physical ground connection and kill the ground loop.