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[Mike Christy]

I would have expected the low current draw for a live band type of event but with the highly compressed extremely bass heavy nature of most EDM I really expected to see a lot higher current draw. 

I am going to keep doing some measurements and put together a spreadsheet to really track my current draw better.  I still have a feeling that my meter isn't the most accurate.   Anyone have a preferred clamp on amp meter?

Ryan

Ryan, Here's a nutty idea, for long term you could get an electronic watt hour meter ( like on the side of your house ) off of ebay, or even a new one from a distributor, and patch it in before your distro.

The key would be to have it programmed to display instantaneous current and power on each leg. A single phase meter would be fairly cheap, poly-phase, a couple hundred pesos. Depending on the programming, you could get QOS readouts as well, and they can tell you of service errrors too - save you from having to meter anything out.

Just thinking...

Mike

[Jeff Bankston]

maybe batman will rent out his nucluer reactor.

[kristianjohnsen]

So I just provided for a fairly large show last weekend.  We had limited power available to be shared between lights and sound.  Video wall had their own dedicated circuits.

We had a 200 Amp 120/208 three phase service.

My system included...
4 Camco Vortex 6 amps for lows, mids and highs.  All run at 2 ohms per channel on all band passes.
2 Camco Vortex 6 amps for subs at 2.66 ohms per channel.
3 QSC PL380s for subs run at 4 ohms per channel.
4 TCS TA2400 Bridged 4 ohms for a couple extra subs
3 Mackie 1400i two were bridged at 8 ohms for monitor subs and one was stereo 8 ohms for monitor tops

Lighting appeared to be 8 Mac 2000s, 6 Mac 250s and a bunch of LED moving heads.  I didn't pay super close attention to everything that they brought in.

So during the headliner who is a very popular Electronic Dance Music DJ from Italy I decided to measure the current draw of everything just to see where we were at.  Keep in mind that this was for approx 3600-4000 people in the audience and the rig was turned up VERY loud.  Tickling limiter on Subs and highs, 3-6 dB headroom on lows and mids.  Monitors were pegged!

The highest current draw I was able to measure from the combined audio + lighting was 102 Amps on one of the legs, 99 on the other.  They were on all three legs but I only measured the two legs with both audio and lights.  I assume the other was in the 40-50 amps range.
The highest current draw I was able to measure from just the audio was 55 amps on one of the legs and 49 on the other (I only use two legs).

My conclusion is that either my Amp Meter isn't very accurate or we all think we are drawing WAY more current than we actually are.  Possibly a little bit of both.  I am going to go buy a more expensive, hopefully more accurate Amp Meter just to make sure but it really is enlightening to see how much current we are actually using.  I often times don't have time to measure current draw during a show and with the extreme nature of this event it was very eye opening.  I would suggest to everyone around here to do some voltage and current measuring during shows just to see where you are and to make sure that everything is safe.

Happy measuring, Ryan

Ryan, thanks for your interesting post.

I usually stick to the rule-of-thumb that whatever power is delivered to the speakers at full tilt is four times the power drawn from the mains.  In other words, the power drawn from the mains will be one fourth of the power the speakers see when the amps are run into clip.  Just calculate via Ohm's law to get amperes.  I can hardly even remember tripping any breakers whilst using this rule of thumb.

[Mac Kerr]

Ryan, thanks for your interesting post.

I usually stick to the rule-of-thumb that whatever power is delivered to the speakers at full tilt is four times the power drawn from the mains.  In other words, the power drawn from the mains will be one fourth of the power the speakers see when the amps are run into clip.  Just calculate via Ohm's law to get amperes.  I can hardly even remember tripping any breakers whilst using this rule of thumb.

Kristian, what voltage do you use in that calculation? In 120V land that will be twice as many amps as in 240V land.

Mac

[kristianjohnsen]

Kristian, what voltage do you use in that calculation? In 120V land that will be twice as many amps as in 240V land.

Mac

Hello.  I'm in 230ish volt land.

I stick to power (watts) first and then calculate to current (amps) needed to reliably power the system.

In other words:

If the speakers are seeing 3000watts when the amps hit clip I figure the line draw will be one fourth which is 750 watts.  (P/U=I) 750w/230v=3,26a is what I need available to safely power the system.

[Mac Kerr]

Hello.  I'm in 230ish volt land.

I stick to power (watts) first and then calculate to current (amps) needed to reliably power the system.

In other words:

If the speakers are seeing 3000watts when the amps hit clip I figure the line draw will be one fourth which is 750 watts.  (P/U=I) 750w/230v=3,26a is what I need available to safely power the system.

I got the methodology, I was making the point that in the US (where you see 100A 3Ø services) the current will be double what you see.

Mac

[Jeff Bankston]

if you got a tone generator or tape or cd with something like a 50hz,1k,10k tone you can put a short cord with single #10 wires between M&F cord caps and plug that into the wall and plug you amp into that and run a 50hz(providing your flat at 50) tone through a woof amp into a woofer(s) and turn up to just below clip and them put a clamp meter like a fluke 336 and measure the amps on each hot leg. do the same with the amps at other frequencies. use the same amount of speakers that you normally use for each amp. thats the maximum amp draw for the amps in the freq range thay are operating in. the constant tone is gonna make it easy as opposed to music which will give an erratic reading. amp output is not a good way to try to measure supply current draw. my old qsc ab+g amps draw a lot more current from the wall outlet then something like a powersoft class d with the same output.

[kristianjohnsen]

I got the methodology, I was making the point that in the US (where you see 100A 3Ø services) the current will be double what you see.

Mac

Absolutely, I was clarifying for anyone following the thread that might have been unclear.  One needs to punch in the applicable local voltage in the calculation

[kristianjohnsen]

if you got a tone generator or tape or cd with something like a 50hz,1k,10k tone you can put a short cord with single #10 wires between M&F cord caps and plug that into the wall and plug you amp into that and run a 50hz(providing your flat at 50) tone through a woof amp into a woofer(s) and turn up to just below clip and them put a clamp meter like a fluke 336 and measure the amps on each hot leg. do the same with the amps at other frequencies. use the same amount of speakers that you normally use for each amp. thats the maximum amp draw for the amps in the freq range thay are operating in. the constant tone is gonna make it easy as opposed to music which will give an erratic reading. amp output is not a good way to try to measure supply current draw. my old qsc ab+g amps draw a lot more current from the wall outlet then something like a powersoft class d with the same output.

So you run your amps into clip with speakers attached while playing back sine waves???  Poor speakers...

[Jeff Bankston]

So you run your amps into clip with speakers attached while playing back sine waves???  Poor speakers...

you didnt read my post did you ?! i said run to "JUST BELOW CLIP" DUDE !! LEARN TO READ !! always someone trying to belittle a commercial electrician/drummer/singer/pa owner !!

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