# Audio Amplifier Power Output Testing



## ppl

Audio power Amplifiers rated over 5 watts per channel are tested under the FTC rule governing Power ratings of Power Amplifiers for High Fidelity use. This was done because of the lack of available testing standards regarding power output ratings. Prior to 1974 manufactures were free to use what ever power rating would give the Biggest numbers and thus a 10 watt amplifier could easily be rated at 200 watts. A small foot note would sometimes accompany the ratings like IPP
 (Instantaneous Peak Power) IHF (Institute of High fidelity) EIA (Electronic industries association) 

 The Distortion was also tested at whatever frequency that gave the best numbers. This was most often at 1 KHz. Also frequency response was also tested at whatever method gave the best results. This made meaningful comparisons between Power amplifiers meaningless and thus consumers including me petitioned the Government to set up standards so consumers would not be ripped off by Audio equipment manufactures, And to allow direct comparisons between Audio equipment manufactures.

 The government did intervene on behalf of consumers to define standards and these standards were later relaxed as Audio equipment manufactures complained and the EIA lobbied congress on the industry behalf so as to allow a less stringent testing method. Audio power Amplifiers had to be specified as to the Minimum Continuous power output over a specified bandwidth and a defined resistive load and prior to any testing the Amp has to be run at one third power for one hour. The first EIA complaint was the FTC Rule specifying that prior to testing the Amp had to be operated at one third power for one hour so as to get the Amp up to its hottest operating temperature. One third powers generally generate the most heat in a Class b or Class AB output stage due to the large voltage across the conducting transistor. This was later relaxed to one hour accumulated time. See 
http://www.ftc.gov/opa/2000/12/amprule.htm
http://www.electronixwarehouse.com/e...er-ratings.htm
http://www.soundwise.org/gethelp/specratings.htm
http://www.ftc.gov/os/2000/12/amplifierrulenotice.pdf

 This was finally amended to operation at one eighth power output so as to accommodate the inadequate heat sinking and cheep underpowered power supplies the new Multi-channel Home Theater Amplifiers are now using. THX certified are meaningless and just hype. 

 Change could be on they way for the better as more and more people require measurements that better relate to how an Amplifier actual sounds 
http://www.aesitalia.org/Materiale/a...r%20thesis.pdf
http://www.crownmagnetics.com/pdf_files/f1p73sc.pdf
http://www.qscaudio.com/press/in_news/cssbypq.htm

 The definitive standard for testing of Audio Amplifiers as the HP system. this microprocessor based Interments specifications and the generally accepted method of testing Audio equipment is available hear.
http://www.testequipmentdepot.com/us...zers/8903a.htm


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## erix

Thanx!

 ok,
 erix


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## Budgie

Now if only somebody would force the autosound industries to apply the same standards to the products sold in that market!


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## ppl

thay dont and that is why you see chip based Car amps with 20 watts RMS rated at 100 plus watts.


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## Budgie

I actually asked a car stereo "exspert" installer how a car stereo amp could produce more power then it drew from the car electrical system (the "specs" claimed 150 watts per channel, but the power was fused at 10 amps). His response was- It's because of the "trick" power supply built into the amp!!!


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## binary_digit

A friend gave me a 2 channel, 800 Watt, MOSFET, Clean Power Competition series Cantus Bandus 2800. Not clean at all, Closer to 50 watts and not one MOSFET in the entire amp. I'm suprised it has two channels. 
	

	
	
		
		

		
		
	


	




 Peace,
 B_D


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## Canman

Quote:


 _Originally posted by binary_digit _
*A friend gave me a 2 channel, 800 Watt, MOSFET, Clean Power Competition series Cantus Bandus 2800. Not clean at all, Closer to 50 watts and not one MOSFET in the entire amp. I'm suprised it has two channels. 
	

	
	
		
		

		
		
	


	



 B_D * 
 

800 watts...when lightning strikes it


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## binary_digit

I'm thinking that if I lay the chassis across the battery terminals I should be able to get closer to its rated output.
	

	
	
		
		

		
		
	


	




 B_D


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## Czilla9000

Ummm.....does this mean if I try to sell an 8 watt amp as a 1000 watt amp I am going to jail 
	

	
	
		
		

		
		
	


	
















 Great.......all we need is big brother (government) butting into our lives more


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## Budgie

Czilla9000, I have a 1000 watt amp I wanna sell you...........

 "Great.......all we need is big brother (government) butting into our lives more " 

 Thats why I am so against labeling food for ingredients, and those silly warning labels, etc. Let the buyer beware!


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## robert

Quote:


 _Originally posted by Budgie _
*Czilla9000, I have a 1000 watt amp I wanna sell you...........

 "Great.......all we need is big brother (government) butting into our lives more " 

 Thats why I am so against labeling food for ingredients, and those silly warning labels, etc. Let the buyer beware!
	

	
	
		
		

		
		
	


	


* 
 

enough people die, they'll eventually stop buying tainted food. 

 amps may not be as important (then again.......), but call me a pointy headed liberal, someone has to level the playing field. 
	

	
	
		
		

		
		
	


	




 personal injury lawyers rule.


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## taylor

Here's my opinion:

 There should be a sticker called "GovSpec" (government specification) for amplifiers. Having this sticker means the amp passed stringent testing, like the old testing you mentioned. Then you would know that the GovSpec amps were rated properly. But that testing should be optional. High quality amps wouldn't need to be changed to become GovSpec, but for the cheap overrated ones they would either have to lower the ratings or increase the quality to meet govspec.


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## violeta88

Amplifier power ratings aren't the only thing that manufacturers lie about, what about those Minisystems with "3 Way Speakers". The "tweeter" on them are basically decoy tweeters. Oh and those headphones that go from 2 to 40,000 Hz. Yeah, at -70 dB. To prevent manufacturers from lying about their products you'd have to have a rule book the size of an unabridged dictionary!


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## taymat

Quote:


  Originally Posted by *Canman* 
_800 watts...when lightning strikes it_

 

 lol amps are always rated in pmpo in the car world. Speaker sizes are more commonly quoted in cm as well and frequency 'response' without db mentioned. There are CAR systems out there from people like alpine that apparently have a 30hz-30khz range! 
	

	
	
		
		

		
		
	


	




 Its all a numbers race and I'd welcome any intervention by 'Big Brother' to stop it.


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## Edwood

How much is the HP Model 8903A Audio Analyzer? If I had to chose between this and an oscilliscope, which one should I choose?

 Yeah, I know you guys are going to say both.

 -Ed


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## Sycraft

You want real fun with amps and power ratings? Look no farther than the computer world. Do a little searching on some sleazy parts retailers, and you'll invariably come across some computer speakers rated in the hundreds of watts, costing in the single digits. You have a look and, sure enough, they are just little desktop speakers, little 2-3" paper driver units. Like here for example, are a little pair of speakers rated at 280watts. How is that possible, you might ask. I mean I have big floorstanding speakers with dual 7 inch aluminium bass drivers and they are rated to only 200 watts. Never mind the amp it would take to drive them, a 300watt amp is goign to be 2ru at least, probably larger.

 Trick is, you see a little disclaimer next to the raitng somewhere that declares it to be the "PMPO" output. I've never gotten a straight answer on what PMPO stands for, but it doesn't matter because the number basically comes straight out of their ass. It's not even a peak number like you see for some stage amps, meaning it can drive that much only for a little bit, it's basically a completely theoritical number for momentary (as in fraction of a second) output. You persue the data a little farther you find they are 3watts RMS, which sounds about right for speakers that size.

 It is, by far, the most inflated BS rating I've ever seen. I mean at least some peak claims have something to do with an actual spec, but PMPO seems to just be completely made up.


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## ppl

Quote:


  Originally Posted by *Sycraft* 
_You want real fun with amps and power ratings? Look no farther than the computer world. Do a little searching on some sleazy parts retailers, and you'll invariably come across some computer speakers rated in the hundreds of watts, costing in the single digits. You have a look and, sure enough, they are just little desktop speakers, little 2-3" paper driver units. Like here for example, are a little pair of speakers rated at 280watts. How is that possible, you might ask. I mean I have big floorstanding speakers with dual 7 inch aluminium bass drivers and they are rated to only 200 watts. Never mind the amp it would take to drive them, a 300watt amp is goign to be 2ru at least, probably larger.

 Trick is, you see a little disclaimer next to the raitng somewhere that declares it to be the "PMPO" output. I've never gotten a straight answer on what PMPO stands for, but it doesn't matter because the number basically comes straight out of their ass. It's not even a peak number like you see for some stage amps, meaning it can drive that much only for a little bit, it's basically a completely theoritical number for momentary (as in fraction of a second) output. You persue the data a little farther you find they are 3watts RMS, which sounds about right for speakers that size.

 It is, by far, the most inflated BS rating I've ever seen. I mean at least some peak claims have something to do with an actual spec, but PMPO seems to just be completely made up._

 

LOL In my day it was called IPP Meaning Instantaneous Peak to Peak. how they put a power rating to that was take the max positive voltage and add it to the max negative swing yes i know its strange how marketing EE's can add equal positive and negative numbers and get twice what you started with hears a link that gets further into this rating
http://www.electronixwarehouse.com/e...er-ratings.htm

 The interesting thing about car Audio is that Only home High fidelity Amplifiers were covered and so left to there own devices we again have dishonest mass market manufactures inflating reality once again Further proving that Government monitoring of the Business ethics of corporations (Can you say Enron)
http://www.time.com/time/2002/enron/

 Next down the list was firm the then Institute of High Fidelity (IHF) This society was like the AES is in Pro Audio Today an full on Lobbying origination to promote the interests of its members that were comprised of High Fidelity Equipment manufactures. Thus all Specificications had a standard IHF rating. FM Tuners, Preamps Amplifiers and most High fidelity and speakers were rated in power capacity by the IHF standard.
http://stereophile.com/asweseeit/489/

 When will the madness end?


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## silvervarg

Quote:


 a 300watt amp is goign to be 2ru at least 
 

Actually the digital amps (often called class D or class T) can be really amazingly small and still give loads of power, like 400W RMS and don't need big heatsinks.
 The power supply for such an amp is typically still rather big though. With a switching supply that might be possible to make quite small too.
 Not that I have seen any digital amp or switched high quality PSU in any computer speakers yet, but it should be technically possible to make one.


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## Garbz

These specs don't require all channels to be loaded correct? A friend tested a 5x100watt yamaha receiver with all channels loaded. It ended up clipping at around 12-20watts / channel. My guess is inadequate PSU. An individual channel had no problems putting out close to 100watt into the load. I was always wondering how their 5x100w amp could produce taht power with a transformer half the size of my 2x70w amp.


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## dr_digits

Quote:


  Originally Posted by *Sycraft* 
_ I've never gotten a straight answer on what PMPO stands for, but it doesn't matter because the number basically comes straight out of their ass._

 

Peak Music Power Output is the acronym, but I don't know how they are supposed to measure it.


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## 00940

Quote:


  Originally Posted by *dr_digits* 
_Peak Music Power Output is the acronym, but I don't know how they are supposed to measure it._

 

here's a good summary: http://sound.westhost.com/power.htm

  Quote:


 PMPO = PREAL * k

 where PREAL is the real power as calculated by the formula below, and k is a constant whose value is approximately equal to one's grandmother's age, divided by the square root of the distance from the office to the advertisement writer's normal place of abode - measured in millimetres, inches, furlongs, statute miles or pounds per square inch - as appropriate, to provide the number you first thought of. 
 

The rest of the article is (a bit) more serious


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## Regal1975

As with in every industry, car audio ratings are dependant on a quality manufacturer. There are companies like alpine who make amplifiers rated at 200watts and they are barely capable of 80 clean, but they also make products that are highly underrated. Then there are companies such as USAMPS who make amps rated at 80 watts that will tolerate extreme abuse and are capable of using every bit of current their 40 amp fusing allows. I still remember my shock when i swapped from a 5x100 pioneer home theater to a 70x7 HK avr 525 and founf out that that 70watts was a whole helluva lot stronger than the 100 watts from the pioneer.


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## meta03

The 8903A is one of my favourite peices of test equipment. There's newer much fancier stuff at the development lab I work in, but nothing beats that box for ease of use and functionality when it comes to designing solutions for audio systems. The cost of buying one yourself isn't too bad, I think auctions start at $500 when they're on eBay, but . . . and here's a big but . . . they do have to be calibrated every year. I know, cause when you're doing measurements . . . and numbers between your function generator and your distortion analyzer disagree. . . and you have to kinda guess and the numbers for the math, things can get painful real fast. The calibration (by Agilent) costs about as much as the box does.
 Oh, and just to let everyone know HP no longer makes test and measurement equipment, Agilent is what became of that division of HP. So I guess it should be called the "Agilent Method" from now on.
 Rane also has one of the most comprehensive sections about testing and the correct way of doing it, on their website. Check it out! Knowledge is your best friend.


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## LawnGnome

Quote:


  Originally Posted by *Budgie* /img/forum/go_quote.gif 
_I actually asked a car stereo "exspert" installer how a car stereo amp could produce more power then it drew from the car electrical system (the "specs" claimed 150 watts per channel, but the power was fused at 10 amps). His response was- It's because of the "trick" power supply built into the amp!!! 
	

	
	
		
		

		
		
	


	


_

 

I know this posts is several years old.

 But it's possible to have peak power that high because of capacitors and slow burn fuses.


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## Budgie

(finally I am back on line after more then a year! been some hard times for me lately.)

 Power out can not exceed power in. Law of physics. You can charge up a cap slowly, then discharge it rapidly, but the equation will still show less then 100% efficency.


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## tomb

Quote:


  Originally Posted by *Budgie* /img/forum/go_quote.gif 
_(finally I am back on line after more then a year! been some hard times for me lately.)

 Power out can not exceed power in. Law of physics. You can charge up a cap slowly, then discharge it rapidly, but the equation will still show less then 100% efficency._

 

Sorry for your hard times and glad to have you back.
	

	
	
		
		

		
		
	


	




 About power - you're actually thinking about Energy. That is, the fundamental conservation of energy: it can't be created or destroyed, just transferred from one form/place to another - e.g., Energy In must equal Energy Stored + Energy Out.

 Power is Energy per Time. Decrease Time, as in a "Peak", then Power may increase for the same level of Energy. As you correctly state, some of the Energy will be lost in the attempt to store it at less than 100% efficiency in the capacitors. However, the capacitors can release that Energy in much less Time, resulting in greater Power Peaks than the steady state Power that's input.

 As LawnGnome says, as long as the fuses are slo-blo, they will support the higher Peaks without tripping - assuming that there are lulls in the Power output so that the capacitors can replenish their energy.


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## Budgie

Granted, but, in the before referenced car stereo power amps, I really don't think that is were the inflated power specs are coming from. I think it is much more marketing then realistic specs. The peak power can be higher then the steady state power, however after that peak has discharged those caps, the power will drop to a lower then steady state level while the caps recharge. Averaged over a short time, the overall power input will not exceed the steady state power output.

 I would suggest that a reasonable way to judge the honesty of an amps output power is to compare the power input to the power output in RMS watts. If there is a large difference in specs, as in some home and car audio amps, the specs are going to be questionable. (read = B.S.)


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## justjeff

By far the most powerful, an expensive, an heavy car amp I have ever owned was this old hcca high current amp from orion, which was rated at 25w x 25w @4 ohms. nothing i ever had even came close to it in terms of sheer power. but I think those ratings were a little tweaked for the competion crowd because that amp was stable down to 1/4 ohm mono where it put out 20 - 20,000 800w and if you used say 2 of those you would be in the 100w class, I always wanted to get a dual voice coil 1 or 2 ohm subwoofer and put them face to face isobarick i think they call it in a bandpass encloser wired to see 1/2 ohm just to see what it would do. cause if you take a bunch of speakers to get down to that low ohm you still have all that much more mass to move so dont think the outcome would be all that much more spl, but putting 2 face to face push pull...too bad someone wanted the amp more than me and stole it


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## jim.carr

Quote:


  Originally Posted by *Budgie* /img/forum/go_quote.gif 
_I actually asked a car stereo "exspert" installer how a car stereo amp could produce more power then it drew from the car electrical system (the "specs" claimed 150 watts per channel, but the power was fused at 10 amps). His response was- It's because of the "trick" power supply built into the amp!!! 
	

	
	
		
		

		
		
	


	


_

 

I have seen them around
	

	
	
		
		

		
		
	


	




 300W Pump....


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