Crown Macrotech 17amp load

[c2thej2theizzo]

I usually run my macro techs only at festies, with power stations where I know I have the right current. Macro techs draw 17amps (unlike most that only require 15) This Weekend I am in a gymnasium and noone there can give me info on the electricity. I may not have a 20 amp circuit available. I have run on 15 before but not two amps at the same time and not with a whole stage of amps possibly in the same circuit.

Is there some kind of current transformer that pick up that will get me the current I need to make sure I dont blow any circuits?

 

[T-Bird]

Hi.

Is there some kind of current transformer that pick up that will get me the current I need to make sure I dont blow any circuits?

No.

The amp will try to draw the same power regardless of the current, so if there's not enough power, raising the current (and lowering the voltage, obviously) will do nothing.
Well, not exactly nothing, You'd lose additional ~5% on transformer losses.

A some kind of soft start device could help, but I don't know that any such devices exist for audio equipment.

And even if there was, You'd probably be able to buy two new amps for a cost of one "soft starter".

Regards
Sam

 

[projectMalamute]

No, all the power you use has to come from somewhere. If you are getting 20 amps to the amp rack all of those 20 amps have to come out of the wall, no massaging is going to change that situation.

However, you might not need as much power as you think:

You will notice that current draw numbers are usually rated at full, 1/3rd, and 1/8th power on spec sheets. Very generally that breaks down like this:

Full current draw is the clip lights on all the time. Real world it is almost impossible to use an amp in this manner. Unless you are providing sound for a sine wave ensemble.

Even if you are hitting the clip limiter with every transient and running in to grotesque distortion your average power draw is probably about 1/3rd of whatever the amp is rated at. Especially with something like a Macrotech. Massive storage in the capacitor bank in that power supply.

Occasionally hitting the clip limiters on the loudest transients roughly translates to 1/8th power. If you want things to sound good this is real world how much usable power you have on tap.

I ran two Crest CA9's (the breakers on those are 21 amps each) right up to the clip limiters four nights a week for over a year at a house gig I used to have, both on a single 20 amp circuit. Never blew a breaker.

So you might be alright. I'd turn the amps on one at a time.

 

[c2thej2theizzo]

Thx guys, I didnt think there was anything for scaling current ... just voltage,

Guess I'll just run them safely, maybe pickup something used, Or try to just run one for mains, my other equipment is in use at another party. Most newer gyms have good wiring for doing events but I'm at an old school, so we'll see what I can come up with, Guess I'll bring extra extension cords, maybe I'll bring my honda generator just in case.

 

[Steve]

If it is a legitimate "gymnasium". the NEC will require that the minimum circuit size be not less that 20 A,

 

[ggunn]

Thx guys, I didnt think there was anything for scaling current ... just voltage.

You can't scale one without scaling the other. For a given power draw the product of voltage and current is constant. If you double one, you cut the other in half. Minus transformer losses, of course.

 

[Vinny D]

On a 20a circuit I can get away with running (2) Crown Itech 8000, and (2) QSC PLX3002.
Granted, the Itech's are very effecient but it still is pretty impressive to get that many big amps running off of one circuit.
If you keep your amps just tickling the clip limiters you should be fine.

 

[ggunn]

On a 20a circuit I can get away with running (2) Crown Itech 8000, and (2) QSC PLX3002.
Granted, the Itech's are very effecient but it still is pretty impressive to get that many big amps running off of one circuit.
If you keep your amps just tickling the clip limiters you should be fine.

Another thing - circuit breakers are not instantaneous devices. If your power amps draw more than 20A (even a lot more) on a 20A circuit during the occasional transient, the breaker will not open and the building wiring will be fine.

 

[Hactar]

Can you get two separate 15 amp breakers, one per amp?

projectMalamute is right, even maxing out the amps, you will probably not reach full 17 amp draw.
Assuming you aren't running a 1kHz sine wave at the absolutely loudest possible, I don't think you will need 17 amps.