In december my band did this gig where we got a sincerely nasty hum in most of our equipment. Especially my tube amp in combination with my tele sounded crazy. It wasn't possible to use it and I wound up using my backup V-Amp 2 and a humbucker guitar direct into the PA. Later on we found out that it was the dimmers for the lights in the ceiling that were causing the problems. When the lights were fully off or on there was no hum but in between it was crazy. Live and learn.