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Old 30th August 2011, 08:56 AM   #1
Hayden is offline Hayden  Australia
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Default how can the wattage be?

Am I correct in saying an amp can not be 1000watts when the power consumption on the back of the device says 250w at 50hz?



I have stereo that's 3500watts and I am running it of an Australian power socket which is 240v 10amp = 2400watts

can it really put out more than it is drawing? or is it totally different thing?

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Old 30th August 2011, 09:11 AM   #2
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It's most likely a PMPO rating (Peak Music Power Output). A completely useless (except for marketing purposes) measure

RMS rating is what you really need to look for. It is a theoretical figure that the amp can possibly produce on a transient for a split second.

If the consumption figure is 250W then you are probably looking at most 100W per channel RMS and most probably lower.

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Old 30th August 2011, 09:18 AM   #3
AndrewT is online now AndrewT  Scotland
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Part of the game of the consumer is learning to read the literature so that one buys the goods one needs.

If can be a food mixer, or a radio, or a cordless power drill, or a packet of low fat XXXXX, or an electronic component.
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Old 30th August 2011, 09:33 AM   #4
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The power out cannot exceed the power in. So, you are correct.
I don't even trust RMS ratings unless I know the manufacturer to be reputable and thoroughly honest about their equipment specs.
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Old 30th August 2011, 09:43 AM   #5
AndrewT is online now AndrewT  Scotland
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learn to read the supporting literature.

100W+100W into 8r0+8r0, both channels driven continuously by 1kHz sinewave with a maximum distortion of 0.1% to stand xxx, is completely to unambiguous.
It is also impossible to get more of this output power continuously, than what is put in continuously.

Change the spec to:
127W+127W into 8r0+8r0, 1kHz gated sinewave, 5% duty factor, to standard xyy, is equally valid.

Similarly:
317W+317W into 8r0 peak instantaneous power to standard zyx is quite possible.

The transformer for all these specifications is likely to be somewhere between 200VA and 500VA.
The labeled power rating could be any number the manufacturer cares to put on the device that they think gives guidance to potential users and operators.
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Old 30th August 2011, 09:54 AM   #6
jogi59 is offline jogi59  Germany
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Quote:
Originally Posted by Hayden View Post
Am I correct in saying an amp can not be 1000watts when the power consumption on the back of the device says 250w at 50hz?
No
Many manufacturers measure the power consumption with 1/8 output power. Then 250w seems reasonable.
Quote:
Originally Posted by Hayden View Post
I have stereo that's 3500watts and I am running it of an Australian power socket which is 240v 10amp = 2400watts

can it really put out more than it is drawing? or is it totally different thing?
If you listen to music and not sine waves, it is no problem to get peaks of 3500w out of your 2400w socket.
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Old 30th August 2011, 10:12 AM   #7
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Quote:
Originally Posted by wintermute View Post

RMS rating is what you really need to look for. It is a theoretical figure that the amp can possibly produce on a transient for a split second.
This should have read :

RMS rating is what you really need to look for. PMPO is a theoretical figure that the amp can possibly produce on a transient for a split second.

Tony.
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Old 30th August 2011, 10:17 AM   #8
Mooly is online now Mooly  United Kingdom
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Quote:
Originally Posted by Hayden View Post
Am I correct in saying an amp can not be 1000watts when the power consumption on the back of the device says 250w at 50hz?



I have stereo that's 3500watts and I am running it of an Australian power socket which is 240v 10amp = 2400watts

can it really put out more than it is drawing? or is it totally different thing?

Cheers
Watt are the products in question... can you name names ?
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Old 30th August 2011, 10:21 AM   #9
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250w may seem reasonable, but isn't that then 1/4, not 1/8?

PS thanks for that clarification, wintermute. You really had me confused for a moment.
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Old 30th August 2011, 10:24 AM   #10
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I could probably make an amplifier that runs off some AA batteries that could deliver a kilowatt for a fraction of a second. But I don't think I could honestly advertise it as a 1kW amplifier.
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