Eboy87
Well-Known Member
Ok, so I wanted to get yous guy's opinion on this. The other week, I spent the better part of two hours tracking down a buzz in my system, at least until the SM called places.
Rig: Apogee AE5 mains (1 per side) over Bag End dual 18" subs (model escapes me). Stage fill was another AE5 per side. The mains were driven by an Apogee processor at FOH (A5?) feeding two old JBL amps (Urei 6725 IIRC). The side fills were driven by a Crown XLS402. Yamaha LS9-16 console. The problem was downstream from the console.
Problem: Up until this point (had to have been Thursday of last week, maybe Wednesday), the PA had been running swimmingly. When I powered up before the show, I had a nasty 60Hz hmm coming from the house left stack (subs, mains, and fills), but the house right side was acting normal: no buzz. All our cables run down the same path (signal, speaker, and power). The entire rig is driven off the same circuit at FOH (side fill amp was on-stage, fed from this circuit). I switched cables coming out of the console, going into the amps, even unplugged the power cable running to the XLS. Nothing seemed to get rid of the buzz. Both my boss and myself had never seen, heard rather, a hum quite like this out of only one side of the PA.
THe next day it was fine, but we have our open house coming up here next week that we need the PA for. I want to be ready to tackle the problem from a different angle should this crop up again. Does anyone have any thoughts of what I can try different next time? Has anyone ever heard of a ground loop in half of an amplifier before? Our amps were running in stereo mode. If you need more information, please ask and I'll do my best to answer. We're sort of stumped at this.
Rig: Apogee AE5 mains (1 per side) over Bag End dual 18" subs (model escapes me). Stage fill was another AE5 per side. The mains were driven by an Apogee processor at FOH (A5?) feeding two old JBL amps (Urei 6725 IIRC). The side fills were driven by a Crown XLS402. Yamaha LS9-16 console. The problem was downstream from the console.
Problem: Up until this point (had to have been Thursday of last week, maybe Wednesday), the PA had been running swimmingly. When I powered up before the show, I had a nasty 60Hz hmm coming from the house left stack (subs, mains, and fills), but the house right side was acting normal: no buzz. All our cables run down the same path (signal, speaker, and power). The entire rig is driven off the same circuit at FOH (side fill amp was on-stage, fed from this circuit). I switched cables coming out of the console, going into the amps, even unplugged the power cable running to the XLS. Nothing seemed to get rid of the buzz. Both my boss and myself had never seen, heard rather, a hum quite like this out of only one side of the PA.
THe next day it was fine, but we have our open house coming up here next week that we need the PA for. I want to be ready to tackle the problem from a different angle should this crop up again. Does anyone have any thoughts of what I can try different next time? Has anyone ever heard of a ground loop in half of an amplifier before? Our amps were running in stereo mode. If you need more information, please ask and I'll do my best to answer. We're sort of stumped at this.