If it seems to be happening with those pieces, unhook each piece and try it again, to see if you can narrow it down to which piece it is causing it. If you discover it's one of them, try plugging that one into a different outlet, and see what happens. It could have developed a ground loop.
If everything is plugged into a surge protector, plug that into a different outlet. Even if you have to use an extension cord, for the test. Just make sure you use a HEAVY DUTY ext. cord (heavier than your usual cords). If it quits buzzing, connected to a different outlet, you'll know it's a ground loop. Then you can get the wiring fixed, or you may need to re-arrange furniture.
Good luck!