Waves on the sea are sometimes called gravity waves? I guess this is because it is gravity which provides the potential energy for the oscillation.scott wurcer said:
Is that maximum as in peak, or maximum as in average? I suspect the latter. It is a great pity that DIN did not invent a new name but instead chose to misuse an existing term. That means that people who have never even heard of DIN say 'RMS power' when they don't mean what DIN meant but simply mean 'average power' because they (wrongly) think that you calculate RMS power using RMS voltage.Charles Darwin said:
No, it is not continuous power. It is continuous average power. For a sine wave the actual power keeps varying (at twice the sine wave frequency) from zero up to twice the average. People quote the average and forget that it is an average. Fortunately thermal time constants are such that it is average power which matters. However, someone making infrasonic systems (such as table shakers?) might need to worry about peak power too because his signal is slow. Someone doing RF might have to worry about peak power because of voltage flashover because his time constants are very fast. In audio we don't need to worry.davada said:
A small point... can we give proper attribution to quotes. I had to search for 'advocated' to see that it was Pano who posted that comment some 3 pages back.
The maximum power the amp can deliver continuously over a period of 10 minutes when fed pink noise.
DIN 45500 has become EN61305 some 20 years ago. This did away with minimum requirements and instead is focusing on creating a standard of how to measure the various parameter.
So you don't have to have heard of DIN, you just need to live somewhere in the EU.
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Do amp circuits exist which deliver 1 W at all frequencies to the greatly varying impedance of a loudspeaker ?
Most amps deliver voltage. With them, 2.83 V can be maintained at all frequencies in any impedance provided they can deliver the necessary current.
Voltage driving is the way a frequency response of a driver is measured. If you know the impedance curve of the driver, you can forcast its frequency response, for any driving impedance (passive filter, current output amps) or with the effects of an equalizer ahead of the amp.
You have not addressed the point I made. I assume by 'maximum power' you actually mean maximum average power? The actual maximum is twice this, for sine wave drive.Charles Darwin said:
AndrewT: when a mod puts his hat on and makes a suggestion it might not be wise to query details of his punctuation and try to force him into making a new ruling. Why not accept it as good advice and leave it at that?
The sine wave driving the amplifier, if indeed you are using a sine wave. If you are using something else then the ratio between maximum and average power may be something other than 2.Charles Darwin said:
My point is this: when people say 'power' they almost always mean 'short term average power' but they don't say this. More to the point, in some cases they don't even realise that this is what they mean. Feed 1V RMS sine wave into a 1 ohm resistor. What is the maximum power, minimum power and average power? The right answers are 2W, 0W and 1W. I suspect that some people believe that 1V RMS sine into 1 ohm means constant 1W power (or constant 1W RMS power - whatever that is).
As I mentioned twice already the amp is driven with pink noise according to the EN/DIN standards and RMS is the maximum output it can sustain for 10 minutes in Watts into a stated load, usually 8Ω for domestic and 4Ω for pro amps.
If you got issues with that you might want to just read the regulations yourself and if your issues persist take that up with CENELEC or CEN or which ever body is responsible but until then above is (roughly) the EU-wide definition of amplifier power.
Posts deleted, open discussion of moderation actions is expressly forbidden in the rules. See rule # 12.As for misquoting and non-attribution of quoted material we have had a long standing understanding that that is not done. This should not be news to anyone here.
Further commentary on this subject will result in further sanctions for those involved.
Constant current amps can do a better job of driving a varying impedance with more constant power delivered than a traditional voltage amp can, in general.
That's why so many guitar speakers, especially "classic" or "vintage" speakers, sound subjectively better when driven by a tube amp. A tube amp without a lot of global feedback can act more like a current source than a super low output impedance transistor amp does. That way when the impedance rises with frequency (like any large "full range" speaker would do) the amplifier raises the output voltage. That's why a guitar speaker that sounds full with nice punchy midrange when driven by an old school tube amp sounds dull and muffled when driven by a modern solid state amplifier, sometimes. You know which setup the musician prefers.
Amps having current outputs have some interests, looking for constant power delivered not the slightest one.
Yes, but Jim knew his business *depended* on exceeding quoted performance.
Water coming into an established mine is a well established thing. While it may be a bit less in drought, most deep mines have a constant seepage and thus a constant pumping load.
If his pump huffed and puffed and the mine was wetter than when the horses worked it, he'd have an unhappy customer bad-mouthing him. (I believe he would upgrade or buy-back an engine which did not give complete satisfaction.)
Audio "watts" is an indefinite thing. There is not a definite water-level we have to reach. We can always play softer.
Nobody (but us geeks) has the tools to measure audio watts. Sell a 380 Watts PPO BS RMS^2 (actual output 3 Watts) to the average customer, they won't know.
The OP's actual question should be "When did Watts become RMS?"
The answer is 1974, when the FTC (Federal Trade Commission, part of the US Federal Government) released rules on how commercially sold audio amplifiers were to be tested to give an accurate value of available output power. The rules were actually quite reasonable, and made for some real numbers rather than the gross and perverted exaggerations that other posters here have already given examples of, which were happening in the years before this ruling came out.
The only problem was that the ruling specifies that power is to be given in [ug, OMG, I actually have to type this] "RMS watts."
This guy tells the story pretty well, and he also answers the OP's actual question (the answer seems to be 2010 when the FTC finally corrected itself):
http://www.n4lcd.com/RMS.pdf
Responding to the rest of the original post, it seems things (regarding advertisers' variations in audio power amplifier ratings) may have changed to what they were before 1974. I can offer a guess or two as to why (and it's mostly not because of the 2010 ruling change). The 21st Century markets are international, and anyone in China can sell to any consumer in the USA, and violations of power ratings are so numerous (and on such a small scale for each seller and buyer) that the FTC really doesn't have enough power to stop it. Perhaps eBay could "force" sellers to comply, but eBay surely has bigger problems with the ways both sellers and buyers are scamming on the site.
The answer is 1974, when the FTC (Federal Trade Commission, part of the US Federal Government) released rules on how commercially sold audio amplifiers were to be tested to give an accurate value of available output power. The rules were actually quite reasonable, and made for some real numbers rather than the gross and perverted exaggerations that other posters here have already given examples of, which were happening in the years before this ruling came out.
The only problem was that the ruling specifies that power is to be given in [ug, OMG, I actually have to type this] "RMS watts."
This guy tells the story pretty well, and he also answers the OP's actual question (the answer seems to be 2010 when the FTC finally corrected itself):
http://www.n4lcd.com/RMS.pdf
Responding to the rest of the original post, it seems things (regarding advertisers' variations in audio power amplifier ratings) may have changed to what they were before 1974. I can offer a guess or two as to why (and it's mostly not because of the 2010 ruling change). The 21st Century markets are international, and anyone in China can sell to any consumer in the USA, and violations of power ratings are so numerous (and on such a small scale for each seller and buyer) that the FTC really doesn't have enough power to stop it. Perhaps eBay could "force" sellers to comply, but eBay surely has bigger problems with the ways both sellers and buyers are scamming on the site.
Every customer who has at least one other audio product with a Watt rating has a very rudimentary rule of thumb tool for measuring Watts though.. which is 'literally any other sound reproduction device rated in Watts'. Deviate too massively from basic standards and expectations and 'the average customer,' and even many significantly below the average, will still feel that they've been conned. But often not until after buying and testing of course by which time it's often too late to return.
In USSR there was a State Standard, according to which there were 2 measurements; Nominal power, that means maximal power that the amp can supply as long as needed, without overheating, and a musical power, that is also RMS, but on limited THD. It was specified because crest-factor allowed to cut some corners.
I design my amps such a way so they can run as long as needed on maximal power, before clipping. I.e. no difference between maximal and nominal power.
I design my amps such a way so they can run as long as needed on maximal power, before clipping. I.e. no difference between maximal and nominal power.
Yes, I recall patiently explaining that many times to people, back in the 70s...
plus ça change, plus c'est la même chose....
That was actually an entirely sane way to handle it.
A 100W @8Ohm cont rated amp is actually very much less useful then a 50W @ 8 ohm cont, 600W @ 8 ohm, 1/8th duty cycle design with real program audio, because one will clip a long way before the other, and in reality neither will be thermally limited.
PA Amps are often be specified at 1/8th duty cycle, which pretty much reflects real world usage and allows significant voltage headroom for peaks.
There is no reason to design a AUDIO (As opposed to shaker table) amp to clip at the continuous power rating, that is just throwing away headroom, especially in something like a class D design where SOA and voltage drop across the pass devices is not a concern, in an AB design voltage headroom costs you power dissipation so it is a harder tradeoff there.
REgards, Dan.
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