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What is the absolute lowest level of noise or higher order harmonics that is audible?

Gorgonzola

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A member on another, audiophile site insists that (a) higher-order harmonics are nasty sounding, (b) negative feedback causes high-order harmonics, (c) sufficient negative feedback can reduce higher-order harmonics to the point that they merge with and form part of the sound floor of the device, and (d) there is effectively no level of high-order harmonics, even merged with noise, that is so low it doesn't negatively affect sound perception. (Ergo negative feedback is inherently bad.)

I'm not an engineer or auditory scientist, but I suspect there is some level of harmonics + noise that has no affect on sound perception, (subjective or objective). What might the level be: -120 dB or what?
 
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Speedskater

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A member on another, audiophile site insists that (a) higher-order harmonics are nasty sounding,
That's mostly a game that they play to avoid facing reality!
Both distortion and level are rather complicated.
Are we talking about a skilled A/BX listener and nasty test tracks?
Or an audiophile listening to music in real world conditions?
* * * * * * * * *
the remainder of their comments about negative feedback are nonsense.
 

majingotan

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Ironically their recommended DACs and amps have tons of higher order harmonics, and oh 50-60 Hz PS harmonics/noise that were never attenuated anyways

On a more scientific note, all amps have negative feedback lol (or they'll never be stable), just that some amps don't have a global feedback in hi gain mode but there's local feedback on the inputs always. Even my tube amp has negative feedback at the input, but it does not have it on the outputs, and it has no global feedback as well. However, the signal still gets feedback from the inputs of course
 

Chromatischism

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This is measurable, and has been measured on this site.

Class D analog:

index.php


Vs.

Class AB analog:

index.php



Ask him which higher-order harmonics he's talking about.
 
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Gorgonzola

Gorgonzola

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That's mostly a game that they play to avoid facing reality!
Both distortion and level are rather complicated.
Are we talking about a skilled A/BX listener and nasty test tracks?
Or an audiophile listening to music in real world conditions?

* * * * * * * * *
the remainder of their comments about negative feedback are nonsense.
I'm not sure it's quite an either/or, but he technically he would fit more in the audiophile category. However he has certainly experienced a wide range of high-end equipment both in his own listening space and also that of his many audiophile acquaintances. I can say with certainty that he has firmly established his personal preference based on a lot of listening.
 
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Gorgonzola

Gorgonzola

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This is measurable, and has been measured on this site.

Class D analog:

index.php

...

Ask him which higher-order harmonics he's talking about.
He's talking about 4th order and above, but the higher being progressively worse.

Looking a the Purifi-based amps they have harmonics and noise below -135 dB except for 2nd & 3rd order which he would deem to benign. Personally I'd guess -135 dB to be completely inaudible but I'm looking for other people's opinions.
 

Blumlein 88

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Probably safe to say distortion of -80 db or less is inaudible. Noise needs to be low enough that at max volume and nothing playing you hear nothing.
 
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Gorgonzola

Gorgonzola

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Ironically their recommended DACs and amps have tons of higher order harmonics, and oh 50-60 Hz PS harmonics/noise that were never attenuated anyways

On a more scientific note, all amps have negative feedback lol (or they'll never be stable), just that some amps don't have a global feedback in hi gain mode but there's local feedback on the inputs always. Even my tube amp has negative feedback at the input, but it does not have it on the outputs, and it has no global feedback as well. However, the signal still gets feedback from the inputs of course
The stuff this guy uses is all tube in the category, "If you have to ask the price, you can't afford it".

He is currently, or was recently was, listening to likes of the Aries Cerat Genius , (Eur 19,700), integrated and/or the Amare Musica Entropy Diamond integrated, (Eur 10,655), and/or the Amphion SET42se, (Eur 11,000). Plus he also uses an Aries Cerat Incite preamp.

Presumably they are are all rather high distortion but most of it being 2nd order and maybe some 3rd order harmonics; he consider that 2nd/3rd order serves to mask whatever higher order harmonics that might be present.
 
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Gorgonzola

Gorgonzola

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Probably safe to say distortion of -80 db or less is inaudible. Noise needs to be low enough that at max volume and nothing playing you hear nothing.
... So I'm quite sure he would say a high-order + noise combo at -80 dB would have negative sonic consequences unless it is masked by relatively high levels of 2nd/3rd harmonics.
 

majingotan

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The stuff this guy uses is all tube in the category, "If you have to ask the price, you can't afford it".

He is currently, or was recently was, listening to likes of the Aries Cerat Genius , (Eur 19,700), integrated and/or the Amare Musica Entropy Diamond integrated, (Eur 10,655), and/or the Amphion SET42se, (Eur 11,000). Plus he also uses an Aries Cerat Incite preamp.

Presumably they are are all rather high distortion but most of it being 2nd order and maybe some 3rd order harmonics; he consider that 2nd/3rd order serves to mask whatever higher order harmonics that might be present.

The guy just likes the sound of 2nd order harmonics that's all. A pure tone would not have harmonic frequencies (and beyond -80dB per @Blumlein 88) and is more sonically accurate unlike his system full of 2nd order harmonics. I would agree with him though that having a giant 2nd harmonic and a smaller 3rd harmonic sticking out of an FFT isn't awfully sounding subjectively, but his comment that you must have gigantic 2nd and 3rd harmonic sticking out to have sonic superiority (that's generally an effect of having little to no local feedback and no global feedback) is FOS.
 

Gregss

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The guy just likes the sound of 2nd order harmonics that's all. A pure tone would not have harmonic frequencies (and beyond -80dB per @Blumlein 88) and is more sonically accurate unlike his system full of 2nd order harmonics. I would agree with him though that having a giant 2nd harmonic and a smaller 3rd harmonic sticking out of an FFT isn't awfully sounding subjectively, but his comment that you must have gigantic 2nd and 3rd harmonic sticking out to have sonic superiority (that's generally an effect of having little to no local feedback and no global feedback) is FOS.
Would agree that what with the equipment this guy "likes" he would have to enjoy certain types of distortion. While likely safe to say that most of us on this site want to hear exactly what was generated by the artist and his production staff, not any added distortion at all (or as close as possible to none, period ).
 

levimax

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A member on another, audiophile site insists that (a) higher-order harmonics are nasty sounding, (b) negative feedback causes high-order harmonics, (c) sufficient negative feedback can reduce higher-order harmonics to the point that they merge with and form part of the sound floor of the device, and (d) there is effectively no level of high-order harmonics, even merged with noise, that is so low it doesn't negatively affect sound perception. (Ergo negative feedback is inherently bad.)

I'm not an engineer or auditory scientist, but I suspect there is some level of harmonics + noise that has no affect on sound perception, (subjective or objective). What might the level be: -120 dB or what?
I would try this for yourself. Get REW (free) and there is a "tone generator" that you can add harmonic distortion to any tone at any level for any harmonic and in any combination. See how low you can hear anything even on a single tone for what ever harmonic or combination you like. Trying to hear distortion in music is much harder than a single tone. I think if you do this you will be quite confident that this other member on another site is not correct. Feedback is another issue which this member is not correct on ... this article might help you with your discussions with him https://www.edn.com/negative-feedback-in-audio-amplifiers-why-there-is-no-such-thing-as-too-much/
 

DVDdoug

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The audibility of defects is complicated and I'm not an expert. You need graphs & curves to define it... You can't nail it down to a simple number, although we can usually say that -120dB SINAD is good-enough. CDs have a dynamic range of 96dB but that's generally better than human hearing even if we are listening at 120dB "rock concert levels".

Negative feedback or not, no amplifier (or other electronics) should have audible distortion unless it's over-driven into clipping.

The quietest sound we can hear is about 0dB SPL so a signal-to-noise ratio of 120dB means your music can hit 120dB SPL and when it drops to silence you won't hear any noise.* But in reality the acoustic background noise in your room is probably around 30dB so you'll never hear the background noise (near 0dB SPL) from the speakers. And the nature of the noise matters too... If you have a 1kHz tone at 25dB and acoustic white or pink noise at 30dB, the 1kHz tone won't be completely drowned-out and you'll hear the tone.

Your hearing is also not "flat". It's most sensitive at around 2kHz so you're more likely to hear noise at mid-frequencies.

Your hearing is also most-sensitive to harmonic distortion in the mid-frequencies. And when you get to the highest frequencies you can't hear the harmonics at all! If you can hear to 20kHz and you have an 11kHz signal with lots of harmonic distortion, the 1st harmonic is 22kHz and you can't hear it. You won't be able to tell a square wave from a sine wave! Music (or any natural sound) contains lots of harmonics and that means that you usually can't hear moderate amounts of harmonic distortion even if you can hear the distortion with pure test-tones.

There are other kinds of non-harmonic distortion and those can sound worse, but harmonic distortion (from clipping) is the most common kind of distortion. Clipping generates harmonic distortion, and only odd harmonics. That means if you can hear to 20kHz, you can't hear clipping of any frequencies above 6.6kHz.

And it's true that the higher-order harmonics can be worse. If you have a 100Hz tone with a harmonic at 200Hz it's more likely to be drowned-out that a 1kHz harmonic at the same level. ...The more spread-apart two (or more) simultaneous tones are, the more likely you are to hear them as separate tones.

(Ergo negative feedback is inherently bad.)
Anyone who's studied engineering knows that's just wrong! There's a LOT of nonsense in the "audiophile" community! Negative feedback ("corrective feedback") makes EVERYTHING better. (At least it CAN when done properly.) It can give you lower distortion, lower noise, and flatter frequency response.

Positive feedback is BAD. It's what causes that feedback squeal in a PA system when the microphone picks-up the sound from the speakers and re-amplifies it in an infinite loop. (Positive feedback can be good when you're building an oscillator.)

Negative feedback is how "everything works"... Negative feedback is the steering corrections you make while driving... You can't just point the car straight and expect it to go straight down the road. It's how cruise control holds a steady speed and it's how our self-driving cars will work in the future. Feedback is how airplanes find the airport and how ships find the harbor. It's how your home thermostat works, turning the heat on when it's cold and turning it off when it reaches the target temperature. (My car doesn't have a thermostat. Some newer cars do, but in my car I'm the thermostat and it's up to me to turn the heat up or down or turn the heat off and turn on the AC when it's hot.)





* Plus, you'll probably have a temporary threshold shift (temporary deafness) so you are less able to hear quiet background noise after exposure to loud sound.
 
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Blumlein 88

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Would agree that what with the equipment this guy "likes" he would have to enjoy certain types of distortion. While likely safe to say that most of us on this site want to hear exactly what was generated by the artist and his production staff, not any added distortion at all (or as close as possible to none, period ).
This thread title is a bit off vs what we can say about distortion. The absolute part. What we can hear with pure test tones is one thing and dependent upon frequency and gear used. We probably can't hear less than -60 db or .1% distortion. With music it is almost a certainty -60 db is inaudible and might well be we cannot hear it once it passes below -40 db or 1% distortion. 3% of the right kind of distortion isn't so easy to hear on music while 10% surely is. My guess is the kind of gear your friend has probably also has some small frequency response issues and that might be more about how they sound than distortion.

So when I said -80 db it left some margin for error, and despite that being not all that impressive with modern gear it is good enough. Noise needs to be low enough you don't hear it. Which is a bit more variable depending upon the efficiency of speaker/headphones and noise levels in your listening area. Noise levels vs max output of -100 db are either not going to be a problem or only very rarely will they. Though this is a little simplified.

BTW, a nice bit of software to play around with is pkane's Distort. It lets you dial in any type of distortion you wish in terms of harmonics and relative levels to see what you can and cannot hear. You can get it here for free:

At a minimum it can be entertaining to crank in some heavy 2nd and 3rd and compare to other types. You and your friend could play around with it.

The suggestion up thread to test your ability to hear distortion on a pure tone with REW is another good idea.
 

Waxx

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Anyone who's studied engineering knows that's just wrong! There's a LOT of nonsense in the "audiophile" community! Negative feedback ("corrective feedback") makes EVERYTHING better. (At least it CAN when done properly.) It can give you lower distortion, lower noise, and flatter frequency response.

Positive feedback is BAD. It's what causes that feedback squeal in a PA system when the microphone picks-up the sound from the speakers and re-amplifies it in an infinite loop. (Positive feedback can be good when you're building an oscillator.)

Negative feedback is how "everything works"... Negative feedback is the steering corrections you make while driving... You can't just point the car straight and expect it to go straight down the road. It's how cruise control holds a steady speed and it's how our self-driving cars will work in the future. Feedback is how airplanes find the airport and how ships find the harbor. It's how your home thermostat works, turning the heat on when it's cold and turning it off when it reaches the target temperature. (My car doesn't have a thermostat. Some newer cars do, but in my car I'm the thermostat and it's up to me to turn the heat up or down or turn the heat off and turn on the AC when it's hot.)
Negative feedback got a bad reputation by amp builders who don't know how to use it. But even if you like harmonic distortion like me, negative feedback is needed to regulate the right dose. And if you want it superclean like DVDoug and many others here it's an important tool to eliminate a lot of distiortions to the lowest level possible. Amps without negative feedback are very rarely sounding good in my experience, mostly they are way to distorted, and not only with the good harmonic distortion (2nd and 3th), but also the higher orders and non harmonic distortion. So no, negative feedback is not bad, wrong use or not using the negative feedback is bad, also for coloured amplifiers.
 
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