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Author Topic: Sparky Language Lesson  (Read 9101 times)

John Roberts {JR}

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Re: Sparky Language Lesson
« Reply #50 on: June 26, 2015, 04:29:31 pm »

Unlike most of this topic, I can speak to this part with confidence.

My four sub amps draw 7.5A 1/8-power in 4-ohm bridge. My two FR amps draw 8A, same spec. My two monitor amps, of which I only need one these days thanks to IEMs, draw 9A, same spec. I estimate my all-digital FOH at 3A, and my smallish all-LED light show at 5A. I estimate backline at 7A, everyone uses a modeler but we love our personal cooling fans.

When running full-out for an outdoor event with my distro, I put two sub amps, one FR amp, the monitor amp and FOH on one line. The other line gets everything else. This ends up being a well-balanced ~35A load per line.

I can think of only one time in the last decade that I've run out all 200' of cable. It was to a 100kVa generator, of which I'd directed the promoter to move it away from the stage as it was nowhere near to being a show-quiet model. I distinctly recall bumping the generator output to give a solid 120V at the stage under full system output. I'm completely ignorant of whether that's a "kosher" way to solve such problems, but the show went off without incident.
The main problem with doing that is what happens when you are not drawing full system output? Your 200' going, and coming, through wire, is no longer dropping the same voltage it was at full current.

As long as you don't exceed the over voltage spec for your gear you are Ok...  I'd measure the no-load voltage and if too scary maybe split the difference... 

JR
Quote
Perhaps coincidentally, I think this show was the best my system has ever sounded. Great power, very light breeze, October sunshine on an uncovered stage in a huge university stadium parking lot, with no hard reflective surfaces inside of a quarter-mile in any direction. But I digress.

More often, I only need the 25' tails or the 50' cable, and I can't recall having to tweak anything under those circumstances.
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TJ (Tom) Cornish

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Re: Sparky Language Lesson
« Reply #51 on: June 26, 2015, 04:45:39 pm »

The main problem with doing that is what happens when you are not drawing full system output? Your 200' going, and coming, through wire, is no longer dropping the same voltage it was at full current.

As long as you don't exceed the over voltage spec for your gear you are Ok...  I'd measure the no-load voltage and if too scary maybe split the difference... 

JR
This is good advice.  Also keep in mind that if the generator is marginal or if voltage regulation is poor, when the load is suddenly removed - turning lighting off, the end of an intense song, voltage may spike above the no-load level.

What's the opposite of a brown-out?  A white-out?  A blue-out?
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Timothy J. Trace

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Re: Sparky Language Lesson
« Reply #52 on: June 26, 2015, 05:04:58 pm »

Thanks, guys. Good advice from all.

I can tell you that the generator was a nice CAT, from a well-known rental supplier ---- it just wasn't a noise-dampened model. It was nicely fly-wheeled and regulated, and easily sustained delivery while my subs were cranking.

I don't precisely recall the idle voltage, but I'm sure I metered it, and I'm sure it wasn't high enough to trip any alarms in head....or on my Furmans.
« Last Edit: June 29, 2015, 11:36:08 am by Timothy J. Trace »
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Re: Sparky Language Lesson
« Reply #52 on: June 26, 2015, 05:04:58 pm »


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