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Author Topic: Safe power for Crest CA18?  (Read 4362 times)

Howard Rappaport

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Safe power for Crest CA18?
« on: June 19, 2010, 11:37:19 pm »

Hey all,

I was able to score a Crest CA18 for the club, to power our Turbosound TSW718's (we were slightly underpowering them with a QSC4050, which I'm gonna throw up top to the Turbo THL-2's we got a coupla months ago).

We've only got 20A isolated ground breakers for audio; am I getting myself into trouble? I don't think I'll be running anywhere close to it's max draw...

Any help would be appreciated.
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Ivan Beaver

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Re: Safe power for Crest CA18?
« Reply #1 on: June 20, 2010, 08:31:23 am »

You current draw will depend on several factors.  First your load impedance. You said what model cabinets-but not how many.

The next thing will be how hard you drive the amp and what the program material dynamic range is.

Yes it is in a club.  Is this a jazz club? or a dance club?  Very different thing-current draw wise.

The best way is go ahead and hook it up-see what happens-you have already bought the piece-so it is a little bit late asking whether or not it would work.
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For every complicated question-there is a simple- easy to understand WRONG answer.

Can I have some more talent in the monitors--PLEASE?

Ivan Beaver
dB Audio & Video Inc.
Danley Sound Labs

John Halliburton

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Re: Safe power for Crest CA18?
« Reply #2 on: June 20, 2010, 10:15:12 am »

Howard Rappaport wrote on Sat, 19 June 2010 22:37

Hey all,

I was able to score a Crest CA18 for the club, to power our Turbosound TSW718's (we were slightly underpowering them with a QSC4050, which I'm gonna throw up top to the Turbo THL-2's we got a coupla months ago).

We've only got 20A isolated ground breakers for audio; am I getting myself into trouble? I don't think I'll be running anywhere close to it's max draw...

Any help would be appreciated.


On top of what Ivan said, at the least you need to make sure there is(more than)adequate ventilation to help keep it running cool.  Also, clubs can be nasty dirty places where the gear is stored, make sure they stay clean or get cleaned regularly.

From the manual:

IMPORTANT: To ensure optimum cooling, periodically clean the amplifier fan filters (removable without
tools). Also make certain that there is enough space around the front of the amplifier to allow the cooling
air to escape. If the amplifier is rack-mounted, do not use doors or covers on the front of the rack; the
exhaust air must flow out without resistance. If the amplifiers are to be housed in racks with closed backs,
allow at least one (1) standard rack space of opening in the front of the rack for every four amplifiers.


Further reading in the manual shows power consumption:

Idle Current Draw (120V)                               3.0A
1/8 Power Curr. Draw (typical music cond., 120V/4ohm)  12.0A
1/3 Power Curr. Draw (cont. music cond., 120V/4ohm)    25.0A
Max Curr. Draw (continuous music cond., 120V/ohm)      36.0A


In spite of the dynamic nature of audio power, I'm hunching the dedicated 20a circuit may not be enough juice for this amplifier on sub duty in a "club".  Hopefully it won't be too much of a job for an electrician to pull heavier wire through the pipe, and install a 30a circuit.  Even if Crest designed to function at 100% on a 20a circuit, putting in a solid 30a circuit would not be a bad thing to do.




Best regards,

John
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Howard Rappaport

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Re: Safe power for Crest CA18?
« Reply #3 on: June 20, 2010, 10:54:02 am »

Thanks, Ivan and John.

We're running a pair of TSW718's, 4Ω load.  Typical rock club, 4-7 bands/night.

It'll be in a (thankfully) well-ventilated area; I usually blow the amps out every couple of months; I'll start doing it once a month now.

It's apparent that I'm going to have to convince the club owners to install a 30A breaker.

All this being said, I can't wait to put this beast in and get those Turbo tops running; I'll think we''ll be the only all-Turbo room in NYC at that point...
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John Halliburton

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Re: Safe power for Crest CA18?
« Reply #4 on: June 21, 2010, 09:57:51 am »

Double check the amp cable and plug, it may only be rated for 20a continuous, which means you should just leave it on a 20a circuit.

I can't find any spec on them in the manual.  Perhaps someone from Crest could comment here?

At the least, no front doors on the rack, and you may consider adding more fans in the rack or room.

Best regards,

John
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Howard Rappaport

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Re: Safe power for Crest CA18?
« Reply #5 on: June 21, 2010, 10:49:00 am »

It's a 30A twistlock plug that I'm getting an adapter for today.  

The rack is open back and front; I'm gonna throw a fan in back.

Thanks again.

Howard
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John Halliburton

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Re: Safe power for Crest CA18?
« Reply #6 on: June 21, 2010, 11:57:10 am »

Howard Rappaport wrote on Mon, 21 June 2010 09:49

It's a 30A twistlock plug that I'm getting an adapter for today.  

The rack is open back and front; I'm gonna throw a fan in back.

Thanks again.

Howard



Then I'll make the assumption that the cord is 10ga. and 3 conductor.  Is so, then by all means, have a proper 30a circuit installed from the panel to the receptacle, and at least be all set in that regard.

Best regards,

John
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Howard Rappaport

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Re: Safe power for Crest CA18?
« Reply #7 on: June 21, 2010, 12:27:10 pm »

Just spoke with a tech at Crest; he said it'd be no problem to run it on a 20A circuit, that they put the 30A twisty on it just to get UL cert.  He told me that unless I'm running a 2Ω load, I probably won't be getting near a 20A draw, and that I should be fine.

WOOHOO!  This thing's going on the bottoms TONIGHT!

Thanks again for your help!

-H
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Art Welter

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Re: Safe power for Crest CA18?
« Reply #8 on: June 21, 2010, 01:00:22 pm »

Howard Rappaport wrote on Mon, 21 June 2010 10:27

Just spoke with a tech at Crest; he said it'd be no problem to run it on a 20A circuit, that they put the 30A twisty on it just to get UL cert.  He told me that unless I'm running a 2Ω load, I probably won't be getting near a 20A draw, and that I should be fine.

WOOHOO!  This thing's going on the bottoms TONIGHT!

Thanks again for your help!

-H

I would concur with the Crest tech, I have run the CA18 (loaded at 4 ohm per side)into light clipping with two other amps on one 20 amp circuit, no trips.

That said, the amp draws well over 20 amps peak power, so voltage drop is a concern on a long feed of 12 gauge, the usual gauge used on 20 amp circuits.

If the voltage drops low on the peaks, the amp won't put out the power it is capable of.

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John Halliburton

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Re: Safe power for Crest CA18?
« Reply #9 on: June 21, 2010, 02:40:15 pm »

Art Welter wrote on Mon, 21 June 2010 12:00


I would concur with the Crest tech, I have run the CA18 (loaded at 4 ohm per side)into light clipping with two other amps on one 20 amp circuit, no trips.

That said, the amp draws well over 20 amps peak power, so voltage drop is a concern on a long feed of 12 gauge, the usual gauge used on 20 amp circuits.

If the voltage drops low on the peaks, the amp won't put out the power it is capable of.




This was my concern as well, but given the 4-7day/week club use, along with the unknown cable length,  it certainly wouldn't hurt to put in a 30a circuit and avoid the line sag.

Testing it out as is will certainly be the first step.

Best regards,

John
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