OK, a couple of weeks back i had the biggest show i'd yet done. It was a brass band performance with about 400 high school children doing their thing with the trumpets, trombones and whatnot. The install went well and smooth, the hang went up by lunch (24 EV XLC for FOH and another 10 for sidefill, all driven with GOOD quality gear [Klarkteknik, midas etc]) and the rehearsals were hitchless. 15 mins into the show however, one sidefill stack began humming at ear-slitting levels. Nobody could figure out what was wrong. After about ten minutes, it just went away. How can you prevent things ike this happening? We did all the usual prep work, like testing the leads, replacing dodgy clips etc, but it obviously did no good. All the amps and speaker leads were new nothing had come unplugged, but there were alot of kiddies running around. any suggestions would be appreciated.