simduv2014 Posted March 10, 2015 Share Posted March 10, 2015 Hi guys, Apologies if this question is incredibly basic, but sound really isn't my thing, however as a last minute addition to a lighting gig we have been asked to install a small active sound system around the perimeter of the race track we are currently rigging on. Power for the active cabs is supplied via a 20kva generator, however the mixing desk, which is situated in the main control tower will be powered by on-site mains power. Is linking these two together going to cause any unwanted humming, due to the seperate earths? All and any advice gratefully received. Simon Link to comment Share on other sites More sharing options...
richardash1981 Posted March 10, 2015 Share Posted March 10, 2015 Apologies if this question is incredibly basic, but sound really isn't my thing, however as a last minute addition to a lighting gig we have been asked to install a small active sound system around the perimeter of the race track we are currently rigging on. Power for the active cabs is supplied via a 20kva generator, however the mixing desk, which is situated in the main control tower will be powered by on-site mains power. Is linking these two together going to cause any unwanted humming, due to the seperate earths?Probably. A lightning strike or fault might also be nasty for the equipment and anyone touching it. Firstly, how do you end up with separate earths in the first place, if you have got the generator properly earthed? The better the earthing is all round, the less problems you are likely to have. If the mixer and speakers all have good quality balanced inputs and outputs (probably on XLR connectors), there should be no issues with hum, but there is still a potential issue with current via the ground connections of the audio lead damaging something. If the inputs and outputs are not well balanced, then hum is very likely to occur due to even small ground voltage differences. Inserting a 1:1 audio isolating transformer between the mixer output and the first speakers should stop stray currents, and will also minimise the risk of hum being injected. Put it somewhere where it's hard for someone to touch both sides at once, just in case! Link to comment Share on other sites More sharing options...
TonyMitchell Posted March 10, 2015 Share Posted March 10, 2015 Unpowered cabinets would be better for many reasons: - Rain... If the cabinets are left fully in waterproof covers, to keep the amplifier module covered, any heatsink will have limited effect, increasing the likelihood of overheating/thermal cut out. If they are not covered and it rains, the outcome won't be pretty either. - Sun... On a very hot day, cabinets baking in the sun for a few hours can be uncomfortable to touch, so ditto the above overheating risk. - Only one cable to run to each stand/speaker, as opposed to two. - Keep your mains in a restricted area, rather than having dozens/hundreds of metres of live mains around the perimeter We do lots of these type of events and 9/10 times deploy pairs of E8 on high winch stands, splayed to achieve up to 180deg. coverage from each stand. Lightweight and very loud if they need to be. Don't forget to ballast your stand bases, too many times at events this is overlooked and with a little wind, there's an accident waiting to happen. Link to comment Share on other sites More sharing options...
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