I did an outdoor gig a few years ago when I was not so much experienced as a sound tech or an electrician. The problem started out at power up. I was tied into a sub-panel in the pavilion and had sound on one leg and lights on the other. (Unbalanced load, comes up later). I powered up my stuff and watched the volt meter on my rack swing as usual, maybe a little more. Shorly thereafter the lighting guy shows up and does his thing. He runs his first cue, everything at full to make sure he's not going to snap any breakers during the performance, and my racks all go into shutdown mode. This also happened to be at the same moment that a very noisy ventilation unit kicked on in a nearby food stand. So I went to look into that and finally got it shut off. During the first act, the front man who was bare foot and holding a guitar got zapped in the mouth the first time he approached the mic. Of course the problem had to be with his amp, not my professionally built (by me) distro. So I told him his amp sucked and put a windscreen on the mic so his lips wouldn't touch it. Problems continued throughout the night. After it got dark and Mr. Lights started running cues the line voltage started swinging wildly, from as low as 85 (shutting down my racks) up to above 130 (shutting down my racks). It wasn't too long before I told him to just pick a couple static cues and alternate. At any rate, the following week I was cotinuing my electrical education at the counter of the local electrical distributor and brought up the situation. As it turned out, the guy who services the venue was at the other end of the counter and said that there was a bad neutral connection at the transformer that had caused some serious damage to the food service equipment before it got repaired. Lucky for me my stuff had protection. So here's that balanced load thing. A standard vatiety of electrical service, single phase, has two legs, with 220 volts between them and 120 volts between each leg and ground. If the load is unbalanced between the two legs, (ie. the lighting guy draws more than the sound guy) the difference in amperage shows up on the neutral leg and is safely returned. When the ground floats, then that current has no place to go, and therefore piles up in different places depending on how the ground is bonded. In my case, my expertly constructed distro had the ground and neutral bonded. So that current was running to all sorts of interesting places, such as that amplifier I was so critical of. When that juice got through to his strings, that bare foot guitarist became the quickest route to ground for that current, via his lips. (We made up later and are still friends today) What the code requires for a remote panel like my distro is a separate ground bus, so there's a safe path out. At any rate, that's my embarrasing story. Mr. "I-work-for-an-electrician" letting his ego run away with him and the result being several dozen volts AC passing through the dental work of an innocent musician. The point is make absolutely sure you know what you're doing when you wire things up. In this case it was only mild discomfort. Be very afraid/respectful of electricity, especially when you start to get comfortable around it. I have a pair of linemans pliers that are firmly welded shut from an encounter with a 200 amp main that I was casually working too close to, alone no less. Were it not for some very good insulation, they wouldn't have found me till after the weekend.