# 200 Watts Rating, 35 Watts Draw?

Discussion in 'Amps and Cabs [BG]' started by MuffledBoomy, Apr 17, 2018.

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1. ### MuffledBoomy

Apr 19, 2017
Tulsa
None
I just purchased my first Class D amp and got to say I am pleased so far. But how does an amp rated 200 Watts output have a rated power consumption of 30 Watts? (Info source is the labeling on the amp.)

Feb 11, 2008
Which amp?

3. ### Old Garage-Bander

Jan 31, 2015
Western Hemisphere
30 watts at 120 volts A.C. input. Assuming U.S. (Even OK ).
200 watts at some lower output voltage.

4. ### Plastalmonus

Apr 22, 2017
Melbourne, Australia
10:1 it's an Elf.

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5. ### Bflat

Feb 5, 2008
duty cycle maybe???? or sales bull

Jan 21, 2016
Injiana
Yes. It's an average usage under normal conditions. Nothing to worry about, just a regulatory rating.

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7. ### agedhorseSupporting MemberCommercial User

Feb 12, 2006
Davis, CA (USA)
Development Engineer-Mesa, Product Support-Genz Benz
Regulatory agencies determine this based on 1/8-rated power duty cycle for safety and EMC agency testing. It's a global thing.

Take rated audio power divided by efficiency then multiply by 1/8 duty cycle and you should be close to the minimum rating for average power consumption.

In this case, 200w/85% = 230W

230W x 1/8 = 29W

Nothing marketing, nothing nefarious, just simple math and regulations.

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8. ### Rick JamesInactive

Feb 24, 2007
New Jersey
According to the manual average draw is 30w, maximum is 240w. 30w would be the 1/8 power figure. Most pro-sound power amps are rated for current draw at 1/8 power, because if you run at much more than that you don't have enough headroom. Why they show power draw instead of current draw is unusual, but the two are linear, so it's a valid number.

9. ### MuffledBoomy

Apr 19, 2017
Tulsa
None
Oh, the number is 1/8 power? Like an average between resting and outputtng at good headroom levels?
Thanks for your help. And yes Elf, and I like it so far.

10. ### Rick JamesInactive

Feb 24, 2007
New Jersey
More like the actual power at average playing levels. You use a lot less power than you think you do.

11. ### Downunderwonder

Aug 26, 2009
New Zealand
How many watts of droning sines can you get out of it?

12. ### agedhorseSupporting MemberCommercial User

Feb 12, 2006
Davis, CA (USA)
Development Engineer-Mesa, Product Support-Genz Benz
These days, it's becoming universal to use power rather than current for the ratings because more and more gear is capable of operating from 100-240V and using power GREATLY simplifies managing the back panel graphics.

13. ### Bflat

Feb 5, 2008
200watts until the fuse blows since it wasn't sized for that......its the new math

Last edited: Apr 18, 2018

Jan 21, 2016
Injiana
No one likes a cooked elf. Most amps get warm if you run a sine wave too long at low freq.

15. ### AlexanderB

Feb 25, 2007
Sweden
Well, it is NOT equal to 230 W in this case or any other case, as it is not 15% more... Actually, 200 W/0,85 is a bit over 235 W... Changes nothing in this context, but the glaring "=" looks just... wrong...

But sure, there is no magic numbers in play. It can be a bit frustrating to see how techno-phobic people inte MI fail over and over to grasp the concepts of energy storage, duty cycle, phase angle etc. A 5 kW amp hooked up to a 230 V 10A wall outlet is no perpetum mobile, it will only re-package energy that is available from the power lines.

Last edited: Apr 18, 2018

Jan 21, 2016
Injiana
Andy or Rick would know for sure, bit I think 1/8 of max. is the minimum they can claim for audio.

My network stuff at work is labeled at some insane max. power. That would probably be valid if all interfaces were in use, CPU and memory maxed from activity of an overloaded network, and PoE was used to it maximum available. I had to measure the reality, and got between .5 and 1 amp. Called it 2 Amps for power planning. The UPS/PDUs (fancy power strips) indicate my measurements were correct during peak netwok activity.

If our amps were rated at max. power at the cord, the big hitters would need some special power arrangements. The gear in my datacenter is running off of two 30 Amp 220 VAC dedicated circuits. We run at less than half that.

Last edited: Apr 18, 2018
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17. ### micguy

May 17, 2011
Yes, it's a ratings thing, but part of me imagines there's a small nuclear reactor on board to supply the power it doesn't get from the wall - just like our space probes that go to the outer solar system. If the amp is warm when it's not plugged in, I'd pass.

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Jan 21, 2016
Injiana
I think it was Venus or Saturn we nuked. If little green men live in there, under ground, or under the gasses, I'll bet they're pissed.

19. ### micguy

May 17, 2011
If little green men live on Saturn, they're likely swimming in liquid hydrogen (our present best guess is there is no "ground"/solid surface). A few pellets of Plutonium dispersed over their ocean probably won't wreck their day - I'd guess they're a pretty tough lot.

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20. ### 2tonic

Dec 22, 2015
You, more than anyone, would know!!!

Frankly, I don't mind you all that much!