WATTS: Derate for 1khz vs music. Derate for Class A vs D.

[SIY]

Pink noise has an even lower crest factor

That depends. Pink noise can be shaped to give a wide range of crest factors.

 

[SSS]

Doesn't a multitone signal actually mimic the crest factor of dynamic music? It seems to me that this provides an advantage for power measurements. However, the downside is that its evenly distributed signals don't accurately represent real music. What test signal would be a better representation? Pink noise has an even lower crest factor, and sine waves have an even lower one, moving even further away from "realism."
I don't think that a single signal test would be adequate, and comparing them one-to-one is likely to cause confusion.

If the level of multitone signal decreases with frequency rise then it may be nearer to the music. But music itself has very different spectra, there is no standard of course. So all different measurement types are all approximations. For me measuring amplifiers with several different test types makes most sense in order to get more insight into the amplifier behaviour in different situations. And, different test types cannot really be compared regarding results.

 

[GXAlan]

He measures the power coming out of the speaker with mic, or a sound meter, and uses the speaker sensitivity to calc the power going into the speaker. I guess we are talking past each other so I will try not to get argumentative going forward.

Have you watched the PS Audio video to explain?

That video reviewer SA is unlikely to be accurately sending a true 2V pink noise output. He is taking a sensationalistic approach to talking about amplifier gain.

For such a sensationalistic claim, you could provide people with detailed explanations to reproduce the experiment.

Based upon the data, if you are using an Apple dongle which maxes out at 1V, the Fosi won’t be able to hit its maximum power output while a Yamaha integrated will. The Fosi is weaker actual output power despite similar equal power. But if your source can hit 2V then it doesn’t matter.

If the level of multitone signal decreases with frequency rise then it may be nearer to the music. But music itself has very different spectra, there is no standard of course.

https://www.listeninc.com/wp/media/2023/02/AES-75-M-Noise-Sequence.pdf

This is for testing speakers but would work for electronics too.

 

[Miley_B]

I watched the SA video....
He connected a CD player playing pink noise to the line input of his Yamaha A-S2100 and claims it achieved 108dB in room.
Doing the same with the Fosi V3 he states it was 77dB.
The Yamaha A-S2100 has a V(irtually)U(useless) meter and when using that amplifier at 77dB (the level of the Fosi V3) it reads less than 1w. A measurement distance of 2m is mentioned.
Later in the video he does somewhat clarify that it can achieve a higher SPL if you use a stronger input signal.

 

[SSS]

Have you watched the PS Audio video to explain?

That video reviewer SA is unlikely to be accurately sending a true 2V pink noise output. He is taking a sensationalistic approach to talking about amplifier gain.

For such a sensationalistic claim, you could provide people with detailed explanations to reproduce the experiment.

Based upon the data, if you are using an Apple dongle which maxes out at 1V, the Fosi won’t be able to hit its maximum power output while a Yamaha integrated will. The Fosi is weaker actual output power despite similar equal power. But if your source can hit 2V then it doesn’t matter.

https://www.listeninc.com/wp/media/2023/02/AES-75-M-Noise-Sequence.pdf

This is for testing speakers but would work for electronics too.

M-Noise I knew of already. Did not evaluate yet how it really relates to music. Will view the video. The fact that AES took M-Noise as a standard does not really mean that this is the only valid kind of measure.

 

[antcollinet]

The Scientific Audiophile on youtube made me realize that the power output of amplifiers, when tested with a 1khz tone is much more than when tested for music, especially for class D. Maybe the derate is huge! It is good there are standards, like 1khz, but clearly we need to add a multitone standard that can reasonably represent music.

Does anybody have some good info on this?

For example:

1. Can Class D be tweaked better than class A - to take advantage and inflate 1khz power output. and even more inflated than class A?
2. Can amp designers get more music watts by ignoring the 1khz watts? It may hurt their sales but is still a valid question. I am asking if they can, not if they should.

My feeling is that my Buckeye NCx500 (class D, 700w/ch) needs to be derated such that it performs like a 300W class A. Just a feeling, without any real testing.

Just say music power vs sine wave power

Also no need for A vs D since a D can also be heat-limited if you don't give it a heatsink.

Power is power.

If you are putting 5W (average) into the speakers with music, that is the same power as 5W with a sine wave. The only difference is the peaks will be higher with real music.

 

[SSS]

Watched the M-Noise video from Meyer Sound. Makes sense in order to have a more music complient test signal. Interesting that it is assumed that peak levels in highs are as large as at the lows. This means that an power amplifier needs to deliver the peaks and spikes in the highs with same power and fidelitya as in the lows. But the mean power spectrum is less at the highs.

 

[antcollinet]

Makes sense in order to have a more music complient test signal.

You mean like the multitone signal?

 

[SSS]

Yes in a general way. But the M-Noise is different since the effective power at the highs is lower than the multitone signal provides. Music is somewhat random as the M-Noise is. M-Noise has by intention high peak levels in the highs but not so often than multitone which is continous at high level. Unaltered multitone will probably kill speaker when applied with full power of the amplifier whereas M-Noise should not.

 

[antcollinet]

Yes in a general way. But the M-Noise is different since the effective power at the highs is lower than the multitone signal provides. Music is somewhat random as the M-Noise is. M-Noise has by intention high peak levels in the highs but not so often than multitone which is continous at high level. Unaltered multitone will probably kill speaker when applied with full power of the amplifier whereas M-Noise should not.

Precisely. Multitone creates very much more power in the highs than music does. Music will typically fall off about 40dB from 1Khz up to 20kHz. Multitone has all frequencies at the same power level.

This makes it a much more stringent test for amplifiers than music is (For any electronics in fact). And based on your description, more stringent than your M-Noise signal. Anything that can perform well with multione will have a much easier time of it with real music.

I agree that high power multitone is not something that should be sent to a speaker. But it is a great signal for finding weaknesses in electronics.

 

[SSS]

Precisely. Multitone creates very much more power in the highs than music does. Music will typically fall off about 40dB from 1Khz up to 20kHz. Multitone has all frequencies at the same power level.

This makes it a much more stringent test for amplifiers than music is (For any electronics in fact). And based on your description, more stringent than your M-Noise signal. Anything that can perform well with multione will have a much easier time of it with real music.

I agree that high power multitone is not something that should be sent to a speaker. But it is a great signal for finding weaknesses in electronics.

Agree, multitone is good for amplifier testing at full stress. M-Noise is primarily intended for loudspeaker measurement. Both can be used when one knows what and how to do. This thread started with maximum amplifier power dependent on the test signal type, sinewave 1 kHz vs. multitone. Probably M-Noise is not really helpful to answer this question. Other meaning is welcome.

 

[xrqp]

The M-noise takes into account the crest factor, and more. It is the kind of thing I was hoping for. I left this question at the M-Noise YouTube "Can M noise be used to test amplifiers?". If there is a good reply I will copy it here.

This thread started with maximum amplifier power dependent on the test signal type, sinewave 1 kHz vs. multitone.

Yes, Thanks. Adding some clarification now: 1 kHz vs multitone or vs pink noise , or M-noise, or some signal that is more representative of music than 1kHz.
And a correction to my original post - When I said Class A, I meant Class A or A/B or B.

Power is power.

If you are putting 5W (average) into the speakers with music, that is the same power as 5W with a sine wave. The only difference is the peaks will be higher with real music.

Your sentences are true, but a bit off topic. If you were to say that "an amp giving 5 watts max power with a 1khz input will also give 5 watts max power with music input" then that would be on topic.

 

[antcollinet]

Your sentences are true, but a bit off topic. If you were to say that "an amp giving 5 watts max power with a 1khz input will also give 5 watts max power with music input" then that would be on topic.

It might - it depends on what is the limit. If it is a voltage limit then no, with most music the amp would clip below 5W. If the amp were current limited or thermally limited then most likely the amp would also be able to deliver 5W with music, since the current and/or thermal limit will normally be a longer term limit than the musical peaks. This is often the case when we are talking about the difference between short term, and long term power.

As always the devil is in the detail and we need to be careful about statements we make as absolutes.

 

[Miley_B]

The SA video that this thread is based upon is very misleading.
I'm not clear that you've understood the difference between amplifier gain and an amplifiers maximum output power. Post #15 & #16 will help.
I don't believe it makes sense to be discussing anything further unless this is understood.

 

[xrqp]

I think SA compared the Fosi V3 output when: fed 2V 1khz, and when fed 2V pink noise

This is one of the mistakes I may have made in this thread. Now I think it is wrong. Sorry. But I still am interested how much diff it makes if we max out an amp with test signal of 1kHz vs other input, like pink noise, multitone etc.

 

[xrqp]

The SA video that this thread is based upon is very misleading.
I'm not clear that you've understood the difference between amplifier gain and an amplifiers maximum output power.

The misleading may be more my fault. SA is not misleading. I realize now that the Fosi cannot utilize all its power unless it is fed with an unusually high signal, and the SA test did not do that for good reason. SA did not show how much of the derate was due to signal level, vs signal type. So let's use Erins video instead.

Erin summarizes at time 16:40 that the amp gave 95W with 1kHz and was 18W less with multitone (so got 77W). That is about a 19% reduction. But another amp (I think it was class A/B) he tested earlier in the video had no derate at all. Does anyone have any other hard data like Erins?

 

[voodooless]

But antoher amp (I think it was class A/B) he tested earlier in the video had no derate at all.

Can we please stop using the word “derate”. It’s a pointless notion. We simply have various measurements, and different amp give different numbers for these tests for varying reasons.

 

[pma]

Can we please stop using the word “derate”. It’s a pointless notion. We simply have various measurements, and different amp give different numbers for these tests for varying reasons.

It is a proper word at proper place. Manufacturers are obliged to specify the rated power and there are IEC and FTC standards how to measure it. Not that we have "various measurements", that is a lame excuse. If the amplifier fails to fulfil the standards, then the claimed rated power must be lowered to the level when it fulfils the standards. In other words, derated. ASR should protect the rights and interests of the customers, but, for some suspicious reasons, it rather seems to protect some manufacturers and OEM assemblers and their marketing and business interests. Why? There seems to be a reason.

 

[Miley_B]

The misleading may be more my fault. SA is not misleading. I realize now that the Fosi cannot utilize all its power unless it is fed with an unusually high signal, and the SA test did not do that for good reason

I think it is a very misleading video. What is the good reason to not input an appropriate level signal, I am not aware of it?
The Fosi V3 does not need an unusually high input signal, as was explained in post #15 a $29 headphone dongle can theoretically drive it well into clipping.

I have not watched any of Erins amplifier videos so I cannot comment upon that example.
There is a lengthy ongoing debate thread which you've already been pointed towards upon how to rate an amplifiers output. I'm not going to be drawn into that at this time.

 

[SIY]

FTC standards how to measure it.

"Standards" is not the same as "regulation." Nor are the regulations clear about measurement procedures, not unexpected since they're not written by a professional committee like ASTM, but by lawyers and bureaucrats who couldn't tell you the difference between a Joule and an echidna.

ASR should protect the rights and interests of the customers, but, for some suspicious reasons, it rather seems to protect some manufacturers

Yes, increasing the cost and resource-intensity of consumer products for no actual improvement in the end-use capability is protecting the rights and interests of consumers.