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

xrqp

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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.
 
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I imagine that crest factor would have to be a major part of this story. And you might be surprised... traditional AB amps experience maximum self-heating at about 1/3 of nominal power, which is not the case for Class D. The limiting factor for continuous power output in stereo nCore amps tends to be the shared power supply anyway.
 
The Scientific Audiophile
...isn't. Not even a little.
  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.
Why use Class A as a reference? They are stunningly inefficient. Your 300W Class A amp will throw a kilowatt of heat into the room. I don't know if I've ever even seen a 300W Class A amp since it's so impractical.
 
A 500 watt class D is 500 watts. It is an insane amount of power and you never push that much.

I think it is the opposite of your intuition. A 10 watt class A tube amp may be uprated in effect because a lot of people will like the distortion that sounds like a classic guitar amp.
 
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.
 
A 500 watt class D is 500 watts. It is an insane amount of power and you never push that much.
Never say never.

It’s all about listening distance, speaker efficiency and goals.



I think it is the opposite of your intuition. A 10 watt class A tube amp may be uprated in effect because a lot of people will like the distortion that sounds like a classic guitar amp.

In smaller rooms, 10W may be plenty, especially with high efficiency speakers.

Since clipping is more obnoxious than harmonic distortion, you always want as much power as you can afford while avoiding noise.
A - to take advantage and inflate 1khz power output. and even more inflated than class A?

Watts are a SI unit. It measures the rate of energy transfer over time, so you cannot derate or uprate. You are right that there are amplifiers that might struggle to provide the same amount of joules/second for low frequency versus high frequency output and you are right that the duration of providing said power is also subject to marketing.

It’s not just class, but implementation. The Class AB Onkyo RZ50 AVR does this.
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The biggest marketing trick is duration of power. Some people say maximum power is the amount of power you can push without clipping for at least 0.5 seconds while others will specify maximum power for 2 hours at 50C ambient (122F).
 
500 watts x 2 channels with 88 dB speakers is ~120 dB at 1m. I am quite comfortable saying that I never need 120 dB. In any size of room in a home it is basically immediate permanent hearing damage.

Also, amps don’t need to be signal generators. Any real world music has massive amounts of crest factor. Even a highly compressed track at DR6 means the amp is usually at 25% power.
 
500 watts x 2 channels with 88 dB speakers is ~120 dB at 1m. I am quite comfortable saying that I never need 120 dB. In any size of room in a home it is basically immediate permanent hearing damage.

Agree with all of the above.

But what about a Revel Ultima Salon2 at 20ft listening distance? That gets you to 100 dB.

MBL 101e? Only 80 dB/2.83V efficient.

Or room like this?
Post in thread 'The quest for my hyper speaker - Very Large room dilemma'
https://audiosciencereview.com/foru...er-very-large-room-dilemma.44236/post-1574742

But yes, 500W is plenty for most people :)
 
This is about how much we have to derate the watts going from the watts with a 1khz tone, to the watts with music (which is multitone).
 
This is about how much we have to derate the watts going from the watts with a 1khz tone, to the watts with music (which is multitone).
Watt power is just power independent on one sine tone or multitone. Power is what measured at the output with proper load. At multitone the tones "sit" on the lowest frequency tone. In every moment there is only one voltage and on current which makes the power. Admit that amplifier power supplies are more demanded at low frequencies when conventional and not a switched one. So this can influence the maximum power.
 
500 watts x 2 channels with 88 dB speakers is ~120 dB at 1m. I am quite comfortable saying that I never need 120 dB. In any size of room in a home it is basically immediate permanent hearing damage.

Also, amps don’t need to be signal generators. Any real world music has massive amounts of crest factor. Even a highly compressed track at DR6 means the amp is usually at 25% power.
It's not that simple. Most power is needed at low frequencies, and quite often that is also where impedence hits low minima and steep phase angles get encountered. Then, your amplifier may have to put out a lot of power into 2 Ohms or less. See under modern B&W floorstanders. Nominally 90dB and nominally 8Ohm... but they are actually horrors requiring well designed, powerful amps to drive correctly because of that low impedance in the bass.

I suspect that what is being attibuted to "Scientific Audiophile" here is a garbled version of that message. But it is actually different for different speakers. A smaller, easier to drive speaker doesn't exhibit this behaviour at all (usually because bass rolls off at a higher frequency, of course).

Amplifiers and speakers need to be properly evaluated for use as a pairing, and the room taken into account as well. Forums are full of people who buy big new speakers from the likes of B&W or Magico looking at the nominal figures, and then finding that they have insufficient power to drive the bass or sometimes insufficient gain.
 
This is about how much we have to derate the watts going from the watts with a 1khz tone, to the watts with music (which is multitone).
You don't have to "derate" the measured output at 1kHz at all, because that is what is put out by the amp. It's correct. You have to take everything else (all the other measurements) into account to determine what the amp will do with your speakers.
 
The Fosi V3 is rated 90 watt when using 1khz tone. With pink noise it's output is 0.5 watt. Got that from here at about 50 seconds in, but you need to listen to more than that
The derate is huge. Don't we need to change how we test watts on this site?

The derate for multitone (at Erins audio corner) is not as bad as the derate for pink noise on SA site. Music varies, but my guess is music derate is usually closer to Erins multitone derate, but maybe somewhere in between pink noise and multitone. At time 13:10 he gets into the derate.
 
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The Fosi V3 is rated 90 watt when using 1khz tone. With pink noise it's output is 0.5 watt.

Ahh. Now I get what you are asking. It’s a good point. It’s the demand for standardizing across gain rather than watts.

The Yamaha R-S202 is an integrated amplifier with a preamp and amp.

With 500 mV, it hits 100W into 8 ohms at 0.2% THD. Going from 500 mV to 28.3V is a gain of 35 dB.

The Fosi ZA3 is 26 dB gain, so feeding it 500 mV only gets you about 10V or 12.5 watts.

So it seems like the ZA3 needs to be derated. But wait. If I want the ZA3 to put out 100W, at 26 dB gain, you only need to get up to a 1.4V.

Now, take this $29 DAC

That hits 2V.

Let’s pretend 100W is when clipping occurs.

With the Yamaha, you can go from 0 to 25% volume on the dongle to go to 100W. With the Fosi, you can go from 0-75% on the dongle volume to get 100W. Going past this puts the amp into clipping.

Now, there are negative gain amplifiers and 0 dB gain amplifiers, and that’s a whole different story.
 

This is actually a really good explanation why the volume discussion from the link you said can be confusing.
 
Ahh. Now I get what you are asking. It’s a good point. It’s the demand for standardizing across gain rather than watts.

The Yamaha R-S202 is an integrated amplifier with a preamp and amp.

With 500 mV, it hits 100W into 8 ohms at 0.2% THD. Going from 500 mV to 28.3V is a gain of 35 dB.

The Fosi ZA3 is 26 dB gain, so feeding it 500 mV only gets you about 10V or 12.5 watts.

So it seems like the ZA3 needs to be derated. But wait. If I want the ZA3 to put out 100W, at 26 dB gain, you only need to get up to a 1.4V.

Now, take this $29 DAC

That hits 2V.

Let’s pretend 100W is when clipping occurs.

With the Yamaha, you can go from 0 to 25% volume on the dongle to go to 100W. With the Fosi, you can go from 0-75% on the dongle volume to get 100W. Going past this puts the amp into clipping.

Now, there are negative gain amplifiers and 0 dB gain amplifiers, and that’s a whole different story.
Thanks for this.

To complete the picture, the Fosi is a "power amplifier" despite the volume control, so "Scientific Audiophile" is not even comparing like with like.

The list of amplifiers he shows at 45 seconds into that video reveals that he is in fact (deliberately?) cheating to put down a class of Chinese made low cost power amplifiers.

He also says he attached the CD player (which?) to "line in" when the Fosi would actually have a pre-in, and he doesn't tell us which "87dB" speakers he is using - they could actually be difficult to drive speakers, compounding the issue (he may say what speakers he is using in a different video, and I didn't get to the end of this one, so I may be wrong on that point).

This is why it said here to come to "have fun and learn". Thing is, those videos aren't actually lying - do those things and you get those results, rely on one measurement like SINAD or a single power measurement and things like this result. So, rather than joining in some YouTube outrage, or buying some "giant killer" hype, come here and ask questions and learn from people like @GXAlan.
 
The derate is huge. Don't we need to change how we test watts on this site?
Not being able to push the amp to the max due to too low a gain of the source has nothing to do with the power rating. Besides, the claims are also hard to believe when ASR clearly shows 5W with only 0.213V of input and no power issues at specific frequencies either. It doesn't matter if it's pink noise or not. Clearly, something isn't right here.
 
Let say max output watts is when we have 1% THD.
I think SA compared the Fosi V3 output when: fed 2V 1khz, and when fed 2V pink noise. And the output (at 1%THD) was much less with pink noise. Are you saying that if SA would have fed more volts for the pink noise that he would have got more output (at 1%THD)?

Let say we are testing the watt output of a given amp and we can adjust the input volts and the gain as needed to achieve max output. And we do this 1) with a 100khz input tone. And 2) we do it again changing the input to pink noise. I think they are saying the output in case 2 will often be less, and sometimes way less.
 
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What is your take on the SA video? I think he saying the Fosi V3 gets to much higher watt output when fed a 1khz tone vs pink noise.

I think Erin is saying something similar - what is your take on Erins discussion of 1khz tone vs multitone test signal?

I think currently Amir only uses multitone to test THD. Can one determine multitone power output from that?
If not, can he test output power with multi tone and with pink noise?
 
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