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Output power of amplifiers
Output power of amplifiers
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Old 30th November 2020, 06:13 AM   #21
TonyTecson is offline TonyTecson  Philippines
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Quote:
Originally Posted by forr View Post
W are W .
W RMS is a misnommer for W.
Applying the RMS calculation to power is a nonsense.


Note that the power of an amplifier always emanates from the measure of voltage in V in a load in Ω.
The specifications of amplifiers using voltage in V across load in Ω would clear up the constant confusion about their power.
yes, to be more precise.....

the 1974 FTC ruling is what we go by, ac voltage developed across a dummy load resistor load tells you the power, the sine wave average power, that is at the onset of clipping or a specified THD...

power ratings in any amp is a useful metric to dimension the parts that goes into the making of an amp, any amp.....when music is playing in such an amp, then that is a different ball of wax altogether...

Last edited by TonyTecson; 30th November 2020 at 06:19 AM.
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Old 30th November 2020, 06:17 AM   #22
alcha is offline alcha  France
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I remember reading in an old (very old, about 45-50 years) an article in HiFiNews on how to pass a 3W amplifier into a 100W one, without changing something in it.
Changing the mains voltage (for instance, from 230 to 250V).
Changing the load (from the usual 8ohms to 2 ohms).

Changing the signal, from a pure sinewave to a short pulse.
Changing the bandwith of the measure.
Changing the duration of the measure (instead of something like an hour, just 10 seconds)

Changing the meaning of "power" calculation (from "RMS" to musical to PMPO ...)


Just the miracle of words and "alternative facts" !
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Old 30th November 2020, 06:22 AM   #23
TonyTecson is offline TonyTecson  Philippines
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and all that is due to the fact that music has much lower energy content than the sine waves use as basis for calculations of amplifier designs, so that even a 1000 watt amplifier will be putting out 5 watts real power into a real speaker playing music...
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Old 30th November 2020, 08:06 AM   #24
JMFahey is offline JMFahey  Argentina
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At home , maybe.

For PRO use such as PA, DJ or Musical Instrument, you will not only put out full power,for long hours, but often overdrive it into distortion.
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Old 30th November 2020, 12:44 PM   #25
wg_ski is offline wg_ski  United States
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In the instrument world you get to full power for sure, but in the pro /DJ world you really only approach about 1/4 power on average, maybe about half for the subs when playing tracks like Dark Horse (plug-the-sub-in-the-wall bass). That is with A LOT of distortion. And DJs do live with the distortion, it is PART of what sets the roof on fire and therefore necessary. True professional audio rigs aren’t even run *that* hard continuously - the big companies can’t risk a reputation for poor sound and the blown drivers they would get on every gig. The sound is relatively clean at about 10% of power on average if you are using compressors and limiters properly, which kind of corresponds to the newer “1/8 power” standard they are using now for FTC preconditioning and current draw ratings. It used to be 1/3 power back in the 70’s, and very few amps would make the cut. Very few would make it today. And regardless, the distortion is pretty bad at those kind of levels.
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Old 30th November 2020, 05:01 PM   #26
OldDIY is offline OldDIY
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For speakers, this is the power
a) at which they can work for a long time without damage;
b) withstand a minute;
c) withstand the impulse.
Distortion (THD) is measured at 82 dB
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Old 30th November 2020, 05:13 PM   #27
tvrgeek is offline tvrgeek  United States
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Theater and PA speakers are far more efficient. Usually very high efficiency horns. So they may need 5 times less power for the same sound level.

Bagpipes, or properly warpipes. Designed to be played through the fog to terrorize the enemy. Not in a room. And yea, there is more than one tune written for them even though it seems that is all marching bands can learn. I am not sure what dB they can reach, but as they can cause pain, it is above 110dB.
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Old 1st December 2020, 03:42 AM   #28
spladski is offline spladski  United Kingdom
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In D'Agostino's latest offering the analog meter sensitivity was changed so that customers would have have something to look at. In testing at full power the needles almost bent. Too much to ask for a range switch on a $125,000 amp.
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Old 1st December 2020, 04:04 AM   #29
TonyTecson is offline TonyTecson  Philippines
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still doubtful that what the meter displayed was the real power playing music.....
after all how do you measure power in terms of music? has anyone come up with a metric or procedures?

that meter can slam the stops and get bent but still that is no measure of real power...

i use a power meter feeding the amp to display power while music is playing, power varies when at idle, at low volumes and at very high levels....you will find that it is not constant with use....

this is what i actually use to monitor power real time....https://shopee.ph/20-100A-AC-LCD-Dig...mQFCfoFBtF9OE8

Last edited by TonyTecson; 1st December 2020 at 04:33 AM.
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Old 1st December 2020, 04:46 AM   #30
spladski is offline spladski  United Kingdom
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Meters are useful for setup and periodic calibration, especially for high power rigs. That is if they mean something. Cosmetic meters say more about customers than the amps.
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