Audio terms BS and not BS

[GrimSurfer]

Chipped HDMI.. have arrows

Don't directional cables also have an arrow pointing people to the next higher (more expensive) option?

 

[VonMagnum]

No such thing as RMS power? Tell that one to my old first year DC/AC circuits professor and he'd tear you a new one.

Average power is meaningless without context, especially time. A bunch of peaks measured over a year can "average" a completely worthless number. Your power company likes that, but you may not. Root mean square measures continuous power capability if an amplifier. It may not be perfect, but it's the best estimate of capability I've seen thus far without getting into the capability of driving very low impedance or highly reactive loads loads. (Where are you when I need you Sunfire\Light Star???)

 

[GrimSurfer]

@VonMagnum has offered one of the clearest and most concise posts on the subject of amplifier power measurement.

 

[mtrycrafts]

No such thing as RMS power? Tell that one to my old first year DC/AC circuits professor and he'd tear you a new one.

Average power is meaningless without context, especially time. A bunch of peaks measured over a year can "average" a completely worthless number. Your power company likes that, but you may not. Root mean square measures continuous power capability if an amplifier. It may not be perfect, but it's the best estimate of capability I've seen thus far without getting into the capability of driving very low impedance or highly reactive loads loads. (Where are you when I need you Sunfire\Light Star???)

Since amps are tested with sine waves, please tell us how is that derived? What current and voltage used?
Yes, continuous power is derived but from what I and E?
By the way, how is RMS voltage derived in a sine wave? And current?
Actually, you should do a simple test problem.

 

[GrimSurfer]

http://www.ti.com/lit/an/slea047a/slea047a.pdf

https://www.ecfr.gov/cgi-bin/retrieveECFR?gp=1&SID=94887053abbdb19fa0689f9f44b5761c&ty=HTML&h=L&r=PART&n=pt16.1.432

 

[davidscott]

Don't directional cables also have an arrow pointing people to the next higher (more expensive) option?

Now that is funny. True but funny. And don't get me started on cable batteries.

 

[mtrycrafts]

http://www.ti.com/lit/an/slea047a/slea047a.pdf

Yes, indeed. Right out of there is:
Thus, the power obtained is the average power that the amplifier can sustain.

Thanks for agreeing.
Therefore, average is not RMS. RMS is 70.7%, Average is 50%.

 

[GrimSurfer]

Yes, indeed. Right out of there is:
Thus, the power obtained is the average power that the amplifier can sustain.

Thanks for agreeing.
Therefore, average is not RMS. RMS is 70.7%, Average is 50%.

Those sources stand on their own. Nobody has agreed to anything that I can tell.

Where are you getting both those %s from?

 

[mtrycrafts]

Those sources stand on their own. Nobody has agreed to anything that I can tell.

Where are you getting both those %s from?

RMS is .707 of peak for a sine wave that is used in amp testing. Average power is half of peak power. Or, if you multiply Irms and Erms that is .707 of peak, you get half of peak power.
Or, .707 x .707= .5
It also relates to duty cycle. of a sine wave.

Yes, the sources stand and that link stated average power. Simple. Average is not RMS.
Or, the other way from RMS, you multiply it by 1.414 gives you peak. Or, you multiply average power by 2, you also get peak power.
Try it. Google it.
Yes, you can disagree with your source.

 

[GrimSurfer]

RMS is .707 of peak for a sine wave that is used in amp testing. Average power is half of peak power. Or, if you multiply Irms and Erms that is .707 of peak, you get half of peak power.
Or, .707 x .707= .5
It also relates to duty cycle. of a sine wave.

Yes, the sources stand and that link stated average power. Simple. Average is not RMS.
Or, the other way from RMS, you multiply it by 1.414 gives you peak. Or, you multiply average power by 2, you also get peak power.
Try it. Google it.
Yes, you can disagree with your source.

.707 is the amplitude of the input signal. They chose that to avoid clipping of the input.

An average is a number expressing the central or typical value in a set of data, in particular the mode, median, or (most commonly) the mean, which is calculated by dividing the sum of the values in the set by their number.

(Example: Three steady data points of 100W, 101W, 99W over a given time result in an average output of 100W. 50% has nothing to do with this.)

You speak of duty cycle. You do realize that an amp's output is AC, not DC, right?

https://dewesoft.pro/online/course/voltage-measurement/page/differences-between-peak-average-and-rms-voltage

I'm not aware of any mathematical constant that can be used to convert RMS to peak power. One of the reasons for this is that while RMS measurement is derived according to a defined standard, peak power has no defined standard.

Now people generally say that RMS values are about half peak values, but there is no scientific or mathematical basis for such claims. Google it.

 

[mtrycrafts]

.707 is the amplitude of the input signal. They chose that to avoid clipping of the input.

An average is a number expressing the central or typical value in a set of data, in particular the mode, median, or (most commonly) the mean, which is calculated by dividing the sum of the values in the set by their number.

(Example: Three steady data points of 100W, 101W, 99W over a given time result in an average output of 100W. 50% has nothing to do with this.)

I'm not aware of any mathematical constant that can be used to convert RMS to peak power. One of the reasons for this is that while RMS measurement is derived according to a defined standard, peak power has no defined standard.

Now people generally say that RMS values are about half peak values, but there is no scientific or mathematical basis for such claims. Google it.

Nothing to do with clipping.

https://www.allaboutcircuits.com/tools/rms-voltage-calculator/

https://www.electronics-tutorials.ws/accircuits/rms-voltage.html


RMS is indeed a standard for a sine wave. And indeed you can calculate it with that function. It so happens it is .707 of peak for a sine wave, current or voltage. Period.
From that, you can certainly get exactly 50%, .5 of peak when you multiply RMS I and E.

We are not talking mathematical averages here as your example. RMS is defined. Nothing to do with clipping. Try some examples. Hard numbers.

 

[GrimSurfer]

There is no reliable constant between peak and RMS in an amplifier, because they typically use capacitors to store/release energy to support peak output. Because the number and capacity of these components vary by product, it is impossible to define a constant for conversion.

 

[mtrycrafts]

See the link I provided. It makes things clearer.

There is no reliable constant between peak and RMS in an amplifier, because they typically use varying numbers of capacitors to store/release energy to support peak output.

https://en.wikipedia.org/wiki/Audio_power

You still don't see it. A sine wave has a peak. Period. It has a value in electronics, voltage or current.
RMS is defined. Period. In a sine wave it is .707 of peak voltage. You can certainly derive peak current as well. You multiply the two and you have peak power.
We are not talking which amp, how it is constructed, etc.
You multiply RMS E and I for power, P=IE. Simple. That power will be .5 of peak. Period. .5 is not RMS
10V RMS x 10A RMS = 100W
Peaks are 14.14V x 14.14A = 200W

Lets add this as well
https://en.wikipedia.org/wiki/Root_mean_square

 

[GrimSurfer]

Ok. Now I get you. I thought you were trying to equate peak measurement (PMPO etc) to RMS.

There is no constant to use for this.

If you're talking about the method used to calculate a zero mean wave form (AC),then peak to peak relative to RMS equals to ~2.8/2, or ~1.4. So the relationship is 1.414 (peak) to 1 (RMS). Or, as you say, .707.

The rest follows as you say... including the statement that mean does not equal RMS.

So the discrepancy in our PoVs was over how one word (peak) was being used. Peak may be the same in terms of a pure wave but it's amplitude can vary considerably due to amplifier design depending on what method is used to measure it.

Now I see exactly where you're coming from... and I do agree.

So if we take this forward into a PMPO equivalent where the threshold of clipping rises from 1% (RMS threshold) to 10% (peak threshold), then using the calculation for pure sine waves no longer applies... because the resulting wave is squashed on the top and bottom skewing the outcome of the calculation. I have no clue is any allowances are made for this...

 

[mtrycrafts]

Ok. Now I get you. I thought you were trying to equate peak measurement (PMPO etc) to RMS.

There is no constant to use for this.

If you're talking about the method used to calculate a zero mean wave form (AC),then peak to peak relative to RMS equals to ~2.8/2, or ~1.4. So the relationship is 1.414 (peak) to 1 (RMS). Or, as you say, .707.

The rest follows as you say... including the statement that mean does not equal RMS.

So the discrepancy in our PoVs was over how one word (peak) was being used. Peak may be the same in terms of a pure wave but it's amplitude can vary considerably due to amplifier design depending on what method is used to measure it.

Now I see exactly where you're coming from... and I do agree.

So if we take this forward into a PMPO equivalent where the threshold of clipping rises from 1% (RMS threshold) to 10% (peak threshold), then using the calculation for pure sine waves no longer applies... because the resulting wave is squashed on the top and bottom skewing the outcome of the calculation. I have no clue is any allowances are made for this...

Yes, glad we are on the same page. The term RMS power is misused since we know the math of a sign wave.

 

[GrimSurfer]

Yes, glad we are on the same page. The term RMS power is misused since we know the math of a sign wave.

Yup. Totally.

I think @VonMagnum is on the same page too, as he was using time as the basis for underlining the difference between RMS and PMPO-type (aka peak power, aka IHF, aka music power) measurements.

In those latter cases, the amplitude of the sine wave is measured over a short period of time (eg. 50 ms burst). This allows the power stage or gain stage of the amp to cope better than if it were asked to sustain that gain over a longer time domain (as would be the case if one measured output using the RMS method). It might also allow overshoot to be considered as the peak of the sine wave... but I don't know this for certain.

 

[GrimSurfer]

Now that we've beat that issue to death...

In another post, @WaynePflughaupt makes a very good point about how weighting is used (and possibly misused) with regard to noise specs:

https://forums.audioholics.com/forums/threads/think-i-could-use-help-running-my-crown-xls-1502s-correctly.114285/#post-1305495

 

[mtrycrafts]

Yup. Totally.

I think @VonMagnum is on the same page too, as he was using time as the basis for underlining the difference between RMS and PMPO-type (aka peak power, aka IHF, aka music power) measurements.

In those latter cases, the amplitude of the sine wave is measured over a short period of time (eg. 50 ms burst). This allows the power stage or gain stage of the amp to cope better than if it were asked to sustain that gain over a longer time domain (as would be the case if one measured output using the RMS method). It might also allow overshoot to be considered as the peak of the sine wave... but I don't know this for certain.

Yes, to all, but. we can just see if the RMS power terminology is correct or not without invoking an amp, signal duration or anything.

RMS is a function calculation, derivatives. Sine wave on a paper can be stated to have an RMS value based on a peak value as that goes hand in hand.

One can plot the power sine wave from that example above, 10V RMS and 14.14V peak and same current.
That will produce a peak of power of 200W. What is called RMS power incorrectly would have to be RMS of that 200W which it is not since the real power from the RMS E and I is 100W.
That is my beef, the nomenclature, not when it clips, how much, what distortions, music power or something else. Since RMS is a continuous unit, so is power and from the numbers it has to be average.
But, one can call it whatever, the numbers calced is the same.

 

[mtrycrafts]

Now that we've beat that issue to death...

In another post, @WaynePflughaupt makes a very good point about how weighting is used (and possibly misused) with regard to noise specs:

https://forums.audioholics.com/forums/threads/think-i-could-use-help-running-my-crown-xls-1502s-correctly.114285/#post-1305495

And, that is another story that I will leave alone.

 

[VonMagnum]

I'm visiting at a family member's house right now and was just going to post a link on how to calculate it from peak, peak to peak or average, but I see it's already been posted.

You're really looking at what you can get out of a system that keeps diving through a zero point (waveform typically measured with a basic sin wave). Peak is misleading and therefore used extensively in advertising! Caps can increase temporary current reserves, but they don't change continuous power capability.