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Are all watts equal?

egellings said:
The watt, like the meter or yard, is a unit of measure.
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Except an electrical watt is derived from 2 other units,volts and amps and both need to be in there complex form, ie the phase between them is as important as there amplitude. In its most basic form it involves the integral of the 2 signals (V and I) so is a bit more complex than a yard.

Amp watts are the same if the measurements are the same. Those measurements should include complex loads and low frequencies because these will stress some amps more than others.
 
Indeed, I'm not saying the class D amps are bad, I'm saying you need to consider their input sensitivity when purchasing your amp,
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Yes, you should check that, for any class. The class of the amplifier is not related to gain.

Also, pro line level is higher than consumer line level so some pro amps (usually with XLR inputs) may not have enough gain/sensitivity when used with consumer equipment. But "line level" isn't usually calibrated (especially at home) so you have to check the specs of the amplifier and whatever is driving it, especially if the amplifier has XLR inputs.
 
In science all Watts are equal, of course. But in amplifier marketing: no. There are a lot of, how shall we say?, rather ambitious numbers there, especially in pro-audio. (There are amps you can buy on Sweetwater with spec Watts that would need a dryer power connector but they just got the regular 120V 15A.) But I'm not sure that the magnitude of the marketing multiplier is larger in the case of class D than it is for A.

kandamrgam said:
I often hear sentiments like 10W from class-D amplifier is equivalent of 5W from a class-A amplifier.
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Where do you often hear that?
 
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Gain is cheap. In the vast majority of cases for the designer, it's free, just the change of a resistor value in the feedback loop.
 
Cbdb2 said:
Except an electrical watt is derived from 2 other units,volts and amps and both need to be in there complex form, ie the phase between them is as important as there amplitude. In its most basic form it involves the integral of the 2 signals (V and I) so is a bit more complex than a yard.

Amp watts are the same if the measurements are the same. Those measurements should include complex loads and low frequencies because these will stress some amps more than others.
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Agree; the angle between the imaginary and real parts matters. If it's 0, then you have a resistor.
 
A watt is a watt. Energy measure. Doesn't care if it transforms into heat or controlled/uncontrolled movement energy. But the result matters to us, and many measurable factors control the effectiveness of amplification Watts into accurate music presentation. And repeatability is science-engineering, magnificent singularities are chancy "magic".
 
pablolie said:
A watt is a watt. Energy measure. Doesn't care if it transforms into heat or controlled/uncontrolled movement energy. But the result matters to us, and many measurable factors control the effectiveness of amplification Watts into accurate music presentation. And repeatability is science-engineering, magnificent singularities are chancy "magic".
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Technically power. Integrate power over time and one gets energy. I know you know that, but there seem to also be mathematically and physical science-ly inclined folks here and some of them get persnickety about such matters. ;)
 
Unit of energy is, as far as I recall, a Joule.

Seems to me that, as far as amplifier manufacturer's power claims go... very few Watts are the same!
 
Chr1 said:
Unit of energy is, as far as I recall, a Joule.

Seems to me that, as far as amplifier manufacturer's power claims go... very few Watts are the same!
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Indeed!

It's a derived unit.
...and the SI units for the Joule are...
1J = 1 kg • m^2 • sec^-2

... and the SI units for the Watt are...
1 W = 1 J/sec = 1 kg • m^2 • sec^-3

You can't sell people power* -- but you can sell 'em energy.
That's why you (or at least I) have this utilitarian grey meter on the corner of my house that measures my (net) energy consumption ... in units of kilowatt-hours.

We can express amplifier power output in units of horsepower (hp) if we wish:
1 watt** = 746 hp

EDIT: oops! :facepalm:
746 watt** = 1 hp
shout out to @DVDdoug (below) for being gentle 'stead of going for the juggler jugular. ;)
DVDdoug

Post in thread 'Are all watts equal?'

1 watt** = 746 hp
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You've got that reversed. ;) 1W won't move a car and my car stereo doesn't require thousands of horsepower...
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I don't think there is such a thing as RMS horsepower, FWIW. You'd have to ask your average horse.*** ;)

_____________________
* Mustangs and Corvettes notwithstanding :cool: (or, e.g., Lamborghinis and Bugattis, for those outside the US)
** uppercase or lowercase "W"? I mean, it's named after the guy (James Watt).
*** Unless, of course the horse, of course, is the famous Mr. Ed. :)
 
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When Mr Ed comes into the thread, you know that the final word has been spoken! Mr Ed is very cool and very smart. Mr Ed for the win.
 
Yahbut, Mr. Ed would saunter along unless one applied the whip. After the whip, Mr. Ed would jump forward in a burst of energy right before planting a hard hoof in the posterior of the whip-applier.

Think of the whip as voltage. Power doesn't have RMS, but voltage does, and the RMS of the signal described by the voltage waveform demands power. Describing the voltage correctly is a first step to quantifying the needed current and therefore the power.

So, Mr. Ed notwithstanding, I take RMS Power to be a sloppy shortcut for "Power associated with the RMS voltage of a test signal."

Rick "sore butt" Denney
 
rdenney said:
So, Mr. Ed notwithstanding, I take RMS Power to be a sloppy shortcut for "Power associated with the RMS voltage of a test signal."
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You, me, and the US FTC both ;)
(arithmetic irony intended)
 
PS is a sore butt better or worse than a sackbut?

1758635598087.png
 
1 watt** = 746 hp
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You've got that reversed. ;) 1W won't move a car and my car stereo doesn't require thousands of horsepower...
 
DVDdoug said:
You've got that reversed. ;) 1W won't move a car and my car stereo doesn't require thousands of horsepower...
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I sure did! :facepalm:
I was havin' too much fun!
1 hp = 746 watts
mea culpa, mea culpa, mea maxima culpa.

PS 1 watt might move one of those high efficiency, direct-heated triode cars... :cool:
 
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