Members Unalaska Posted July 14, 2014 Members Share Posted July 14, 2014 Setup: high dollar wedding, expensive band. I send out a pa with a trusted tech. He gets there early, set ups everything just fine. 75kw generator for the outdoor wedding and ceremony (we're doing only the reception). We have our own 50a distro, kitchen has their own and tent lighting has their own distro off the same genny. The genny was set to low rpm by the rental company, my guy switched it to high to get 110v. Actually the meter read 200v 3phase. ?? Ok. Moving on... Basic signal chain: 01v96, rane mq302s eq. Yamaha p5000 (subs ch1, tops ch2) using the amps own crossover. EV sx300 tops over mrx518 subs, 1 per side. Omni outs drive 2 dbx 231 eq's and an alto d4 4 channel amp. All worked great until the band started to soundcheck. The kitchen was cooking, the tent lights were now on. Voltage on the FOH processing rack said 110v. First kick drum hit was crackling real bad, like low voltage bad. Vocals did the same thing. The only solution that worked was using a nearby A&H zed something mixer with L/R driving ch3/4 on the alto amp for mains and aux 1 for 1 mix of monitors. A lot of patching etc and a few phone calls happened in the middle but you get the idea. Main outputs on the little board had to be dimed out to get enough signal to the amp to make it loud enough. The. One of the 4 channels were clipping at all and it seamed to be working like it should. The yamaha amp and subs were bypassed pretty early on in the search for a solution. Today the tech and I went thru and set u exactly how it was set, no issues at all. Clean, clear, loud. I'm not sure what's at fault here? Low voltage on the mixer? Dropped neutral on the distro? I'm scratching my head here. I'm sure no one here could say 100% it's this or that since none of us were there! but maybe there's something I'm missing. On a side note I had 3 other shows and they all had issues, those were all with people rather than gear. Well, the one that had gear issues was because of a person. That's another worst sound of the year thread... Link to comment Share on other sites More sharing options...
Members RoadRanger Posted July 14, 2014 Members Share Posted July 14, 2014 What was the power frequency reading? Changing the RPM of a non-inverter type generator is usually a Really Bad Thing. Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted July 14, 2014 CMS Author Share Posted July 14, 2014 You'd need to know more about the genny. There are several different 3 phase configurations. Most common are 120/208 WYE, and 120/240 Delta. It's possible that the loads on the genny were not balanced across all 3 phases, and this will result in voltage differences from nominal. Whichever phase had the greatest load will have the lowest voltage. The total output of any one phase used alone is lower than 1/3 of the total output of all three phase loads are balanced. Link to comment Share on other sites More sharing options...
Members agedhorse Posted July 14, 2014 Members Share Posted July 14, 2014 Normally, you would set the output of the genny to 208V as the vast majority are 120/208V. 110 volts is not a real standard, it's 120V in the USA, and 108V is the -10% threshold which you would be dangerously near. Add in some voltage drop due to distro and extension cords and you can see where ths is going. Did he verify the voltage with a DMM? Link to comment Share on other sites More sharing options...
Members abzurd Posted July 14, 2014 Members Share Posted July 14, 2014 I don't know squat about gennys but we had a similar experience a few summers ago. It turns out the genny guy simply had the genny set to what amounted to "idle" and never really pushed the right buttons to make it do what it was supposed to do. So the lights ended up dimming with every kick hit. It delayed everything about 30 minutes as I turned off the PA and refused to power it up until the issue was fixed. Link to comment Share on other sites More sharing options...
Members Unalaska Posted July 14, 2014 Author Members Share Posted July 14, 2014 I'm kinda suprised the 01v96 would have a hard time at 110, Ive had the classic 01v on worse power and it's been rock solid. Eh, I dunno Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted July 15, 2014 CMS Author Share Posted July 15, 2014 As Andy implied, you were starting out at about 110v and then had further voltage drops as other equipment was put on line, and then the music starts, lowering available power even further. You could have had voltage in the 90's. Link to comment Share on other sites More sharing options...
Members OneEng Posted July 15, 2014 Members Share Posted July 15, 2014 For those that aren't following why the low voltage is bad, as the voltage drops, the current increases. This can actually damage gear. Some gear will simply turn off if the input voltage drops too low. This is annoying, but doesn't damage the gear. Sorry to hear about your troubles Any time a generator is in use, it is a good idea to have a really good UPS that operates as a full time inverter. This kind of UPS only uses the input AC (through an AC to DC bridge) to charge the battery. The battery is then used to create an AC output through digital manipulation. Link to comment Share on other sites More sharing options...
Members wesg Posted July 16, 2014 Members Share Posted July 16, 2014 Are you sure you were supposed to change the settings on the generator? From a four-wire three-phase 208V feed you can get three 120V circuits - there is 120V between each phase and neutral, each phase is 120 degrees out from the others. We have power bars at work that we plug into 208V outlets that give us three banks of 120V outlets, 15A per bank. There is also another way to supply three-phase 208V, there are three wires and you can get single phase 120V (180 degrees out of phase, common neutral) or 240V (both 120s added up). Please note that I am neither an electrician nor an engineer. This knowledge is stuff I've "picked up" from people who are. I also know that it's a really good idea to balance the work across phases as best as you can. Wes Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted July 17, 2014 CMS Author Share Posted July 17, 2014 The two systems Wes described are 120/208 WYE and 120/240 Delta respectively, which I mentioned earlier. Link to comment Share on other sites More sharing options...
Members Pro Sound Guy Posted July 17, 2014 Members Share Posted July 17, 2014 Those dam NESCOS at weddings will drop the voltage every time Link to comment Share on other sites More sharing options...
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