Purifi Class D

[barrows]

5 hours ago, mocenigo said:

 

They said both things, actually. And it is obvious that they cater to objectivists as well.

 

You mean Hypex, not Mola Mola. Well, they used measurements, and trial and error, not listening.

To be clear, while they have separate company names, Hypex and Mola Mola are essentially the same company:  Hypex is the OE and DIY supply branch, and Mola Mola is the traditional high end branch.  They do not compete with each other, they are even under the same roof.  

[PYP]

7 hours ago, mocenigo said:

You mean Hypex, not Mola Mola. Well, they used measurements, and trial and error, not listening.

Gosh!  Geek Gossip in the audio realm seems rather benign.  

 

I hope that after all the math and measurements there is extensive listening.  Since the Nilai amps include a discrete buffer stage, I'm assuming there was some tuning by ear.  

[mocenigo]

2 hours ago, PYP said:

Gosh!  Geek Gossip in the audio realm seems rather benign.  

 

I hope that after all the math and measurements there is extensive listening.  Since the Nilai amps include a discrete buffer stage, I'm assuming there was some tuning by ear.  

I do not know. Why design something so precise and then ruin it with some changes done by ear? It is like designing a very precise clock and then deciding on the mood of the day whether it should run faster or slower…

[PYP]

5 minutes ago, mocenigo said:

I do not know. Why design something so precise and then ruin it with some changes done by ear? 

Because the subjective reaction is the final measure of success?  But i would suggest asking the audio designers, including speaker designers who use extensive tests/measures, why they use their ears to determine the final product.   I know that the Tambaqui was tweaked according to listening tests.  

[barrows]

37 minutes ago, mocenigo said:

I do not know. Why design something so precise and then ruin it with some changes done by ear? It is like designing a very precise clock and then deciding on the mood of the day whether it should run faster or slower…

I disagree, and most audio designers I hear from do as well.  Bruno Putzeys, for example, has described his design process as doing the maths/simulations first, building a photo, measuring, then listening.  When there are problems found in listening, then he goes to the maths and measurements, and tries to find what the issue(s) are which account for the listening problem.  Then another proto is developed, and so on...  He is never going to "ruin" something by listening, but uses listening to inform his process, and to find new ways to measure for previously less well

understood problems.  Listening is part of the "scientific method" (observation), and never should be ignored.

The "standard set" of audio measurements, such as THD+N at 1 kHz, is woefully inadequate to insure best possible performance with a complex music signal.  So those designers interested in going farther, work with both listening, and measuring, to insure they are getting things right.

Take a look over at ASR measurements, now that they are including the AP 32 tone test.  In many of the components they have measured the SINAD looks great, but the 32 tone test shows a lot more distortion products poking up at audible levels-and even this is simplistic, as the 32 tone test uses evenly spaced tones.

For an example of an advanced measurement, I have heard of some manufacturers who, during development, look at square wave response, at many different frequencies, at many different places in the circuit, to make sure things are operating as predicted in simulation and maths.

For sure all of the above is "engineering", it is not just listening and then making near random changes to try and make it "sound better", but doing the work to get a circuit sounding really good is just not that simple.  These days a merely competent engineer can make a line level circuit look good for THD+N of a single tone, by using a text book IC opamp implementation, but on more complex measurements, that same circuit may exhibit problems.

[leManu]

After many hours of listening to the Nilai500, the "break-in" period seems to have do good.  Or I'm getting used to the sound of it.  Not as warm as my old amp, but I can get why people love this sound.  I also totally enjoy the power, dynamic range and definition of it.  I managed to have a better stereo imaging than I had at first by moving my speakers around.  But still the depth of the soundstage is not as good as before.

 

Which brings me to an issue I still have with the sound.  Every album sounds like I'm sitting in the front row.  Everything is "forward" or "in your face" for lack of better terms.  It's enjoyable for rock music, but for folk or world music it's just too much, and made it impossible for me to have the "suspension of disbelief" I enjoy when listening.  I've tried to pull back and forth my speakers in the room with no real difference.  Is this the way this amp is "tuned"?  Or is this also considered something people enjoy?  Cause I sure don't.  Can it be attenuated with cables or something else?

[mocenigo]

1 hour ago, PYP said:

Because the subjective reaction is the final measure of success?

 

Success of what? 

 

1 hour ago, PYP said:

But i would suggest asking the audio designers, including speaker designers who use extensive tests/measures, why they use their ears to determine the final product. 

I did I, and I do. What they do - at least the serious ones - is usually the following:

- They identify one or more problems that are audible for objects within their BOM limits.

- They identify (or try to understand) what measurable quantity is correlated with this problem.

- They choose a specific approach to change that quantity in order to solve the problem(s).

- Then, they verify by listening whether the problem has been solved. If so, then the considered measurable quantity was the correct one.

- In case only some problems can be solved within the budgetary constraints, they decide which ones to address and to which extent.

 

This does not change the fact that listening is a verification step, not properly a tuning step. At least if they are doing their job seriously. It is not “I like this sound more, so let us do it this way.”

 

1 hour ago, PYP said:

I know that the Tambaqui was tweaked according to listening tests.  

 

If they did, then they would have ruined its performance, and Bruno would never do that. The listening tests followed the procedure above. Listening is a business decision aid.

 

Other manufacturers design with a target of getting a very precise distortion profile, for instance. I am not interested and I consider it anachronistic, since it is cheaper to get a “perfect” amp and tweak in the digital domain. Taste can change, why should one go the expensive of trying several amps instead of changing a profile? So, I am not interested in considering a choice of design activity that is in my opinion bordering on intentional disinformation or fraud.

 

You also mention speakers - this is as of today a different matter in my opinion, since the distortions and frequency response variations are various orders of magnitude higher there. So you often have to choose a particular sound. This can be made also by taste or to follow a “company signature sound.” This is a necessity, but for electronics I posit that this should not be any longer the case.

 

I am not a sworn objectivist. I believe objectivism is a necessity to get to affordable, reliable, absolutely neutral and flexible equipment that we can easily tune to our changing tastes by simply tweaking a configuration profile…

[mocenigo]

1 hour ago, barrows said:

I disagree, and most audio designers I hear from do as well.  Bruno Putzeys, for example, has described his design process as doing the maths/simulations first, building a photo, measuring, then listening.  When there are problems found in listening, then he goes to the maths and measurements, and tries to find what the issue(s) are which account for the listening problem.  Then another proto is developed, and so on...  He is never going to "ruin" something by listening, but uses listening to inform his process, and to find new ways to measure for previously less well

understood problems.  Listening is part of the "scientific method" (observation), and never should be ignored.

The "standard set" of audio measurements, such as THD+N at 1 kHz, is woefully inadequate to insure best possible performance with a complex music signal.  So those designers interested in going farther, work with both listening, and measuring, to insure they are getting things right.

Take a look over at ASR measurements, now that they are including the AP 32 tone test.  In many of the components they have measured the SINAD looks great, but the 32 tone test shows a lot more distortion products poking up at audible levels-and even this is simplistic, as the 32 tone test uses evenly spaced tones.

For an example of an advanced measurement, I have heard of some manufacturers who, during development, look at square wave response, at many different frequencies, at many different places in the circuit, to make sure things are operating as predicted in simulation and maths.

For sure all of the above is "engineering", it is not just listening and then making near random changes to try and make it "sound better", but doing the work to get a circuit sounding really good is just not that simple.  These days a merely competent engineer can make a line level circuit look good for THD+N of a single tone, by using a text book IC opamp implementation, but on more complex measurements, that same circuit may exhibit problems.

then we agree 100%. Read my reply to PYP. What I object to is the concept of “tuning by ear,” which can only ruin things. Using the observation to verify whether a problem has been addressed is different and yo go always back to simulations and prototyping and measurements. You do not do changes by ear that go against measurements (unless the differences are in the realm of the inaudible) if your objective is “hi-fi”.

[Jud]

58 minutes ago, leManu said:

After many hours of listening to the Nilai500, the "break-in" period seems to have do good.  Or I'm getting used to the sound of it.  Not as warm as my old amp, but I can get why people love this sound.  I also totally enjoy the power, dynamic range and definition of it.  I managed to have a better stereo imaging than I had at first by moving my speakers around.  But still the depth of the soundstage is not as good as before.

 

Which brings me to an issue I still have with the sound.  Every album sounds like I'm sitting in the front row.  Everything is "forward" or "in your face" for lack of better terms.  It's enjoyable for rock music, but for folk or world music it's just too much, and made it impossible for me to have the "suspension of disbelief" I enjoy when listening.  I've tried to pull back and forth my speakers in the room with no real difference.  Is this the way this amp is "tuned"?  Or is this also considered something people enjoy?  Cause I sure don't.  Can it be attenuated with cables or something else?

Once again, why inexact trial and error with cables when you can achieve a much more exact and specific solution for your speakers and room with digital room equalization software? This works with not only frequency response but timing/phase (imaging, depth, soundstage) also.

[barrows]

34 minutes ago, mocenigo said:

If they did, then they would have ruined its performance, and Bruno would never do that. The listening tests followed the procedure above. Listening is a business decision aid.

The above is not totally accurate for the Tambaqui:  Bruno has stated that he used a slow(ish) rolloff filter because he thought it sounded better.  Some ASR types questioned this decision, as it resulted in a slight rolloff in FR before 20 kHz, those types at ASR might consider this (ruining its performance).  Digital filter response is a choice, as when considering 44.1 kHz sample rate input there is no "perfect" way to design a digital filter-one is trading off one aspect of performance for another(phase response vs frequency response, vs filter artifacts) and the resulting filter is always a compromise in one (or even two) area(s).  But in general, as above, I agree.

[PYP]

2 hours ago, barrows said:

The above is not totally accurate for the Tambaqui:  Bruno has stated that he used a slow(ish) rolloff filter because he thought it sounded better.  Some ASR types questioned this decision, as it resulted in a slight rolloff in FR before 20 kHz, those types at ASR might consider this (ruining its performance).  Digital filter response is a choice, as when considering 44.1 kHz sample rate input there is no "perfect" way to design a digital filter-one is trading off one aspect of performance for another(phase response vs frequency response, vs filter artifacts) and the resulting filter is always a compromise in one (or even two) area(s).  But in general, as above, I agree.

perfect example.

 

Also, for the Kaluga amps, Kubala-Sosna cable was used to connect the PCB to binding posts.  Why?  Did it measure better?  Or sounded better and measured no worse?

 

When one reads about respected designers who carefully choose certain capacitors, for example, the choice is stated not in terms of measured differences (which one assumes were used to narrow the choices, along with considerations of high rate of production meeting the design specifications, cost, availability, etc.) but preferred "presentation."

 

I'm certainly not advocating for designing by ear, nor making changes that measure worse.  But as Bruno has mentioned, sometimes listeners can hear noise (or choose a better word) that initial measurements missed (as @barrows noted).  He takes that as a challenge to find the measurements that identify the problem area.   Had he not done so, I don't think Class D would today be considered a topology that works for the high-end market.   He blazed the trail.  His work has greatly influenced Grimm Audio, Hypex, Mola Mola, Kii and Purifi.  

 

At any rate, I think there is more agreement than disagreement in how we perceive these issues.   

[fas42]

3 hours ago, leManu said:

After many hours of listening to the Nilai500, the "break-in" period seems to have do good.  Or I'm getting used to the sound of it.  Not as warm as my old amp, but I can get why people love this sound.  I also totally enjoy the power, dynamic range and definition of it.  I managed to have a better stereo imaging than I had at first by moving my speakers around.  But still the depth of the soundstage is not as good as before.

 

3 hours ago, leManu said:

 

Which brings me to an issue I still have with the sound.  Every album sounds like I'm sitting in the front row.  Everything is "forward" or "in your face" for lack of better terms.  It's enjoyable for rock music, but for folk or world music it's just too much, and made it impossible for me to have the "suspension of disbelief" I enjoy when listening.  I've tried to pull back and forth my speakers in the room with no real difference.  Is this the way this amp is "tuned"?  Or is this also considered something people enjoy?  Cause I sure don't.  Can it be attenuated with cables or something else?

 

Okay, this is a typical step on the road to optimum SQ - something I have experienced countless times over the years with a variety of combos of gear. What's happening is that there is a trade off in the type of audible distortion - the older amp had one set of weaknesses; the current one in the context of your rig has a new set of, quite different, weaknesses; what has to be sorted out is a workaround or solution for the current situation.

 

Getting "power, dynamic range and definition" is a critical improvement; the older amp could be pushed into delivering similar, but would take quite a lot of internal work to do this; most likely not worth it, with where current technology is. So, best to evolve what you have now - I had a highly comparable experience with my current active speakers, which gave the type of presentation you describe, when pulled new out of the boxes.

 

So, what to do? The 'workaround' is to play with room, speakers, cables, etc, etc, to "tame" the sound - but is not a solution. The latter is to do experiments to learn where the issues are in the integrity of the playback chain, and once understood, make the necessary, permanent changes to the setup.

 

In my situation, the key weaknesses were sensitivity to noise induced in cables, and mains power noise, plus, good ol' jitter sensitivity. Throw in a touch of contact noise interference and vibration sensitivity, and there was plenty to sort out, .

 

In your case, unless one understood quite thoroughly how it was all set up, it would be close to guesswork to suggest what to address first - hands on, trying this and that, is usually the best initial step.

[PYP]

3 hours ago, leManu said:

After many hours of listening to the Nilai500, the "break-in" period seems to have do good.  Or I'm getting used to the sound of it.  Not as warm as my old amp, but I can get why people love this sound.  I also totally enjoy the power, dynamic range and definition of it.  I managed to have a better stereo imaging than I had at first by moving my speakers around.  But still the depth of the soundstage is not as good as before.

 

Which brings me to an issue I still have with the sound.  Every album sounds like I'm sitting in the front row.  Everything is "forward" or "in your face" for lack of better terms.  It's enjoyable for rock music, but for folk or world music it's just too much, and made it impossible for me to have the "suspension of disbelief" I enjoy when listening.  I've tried to pull back and forth my speakers in the room with no real difference.  Is this the way this amp is "tuned"?  Or is this also considered something people enjoy?  Cause I sure don't.  Can it be attenuated with cables or something else?

I'm not familiar with your gear (that is, haven't heard it), but "in your face" is not what I experience with Ncore-based amps (the version before the latest, improved Nilai).  Of course, this is all relative.  

 

Perhaps if you heard my setup you would react the same way.  I don't think so, given the strong preferences of the other listeners in our household (my wife and cat).  I've had systems in the past that were more forward and she didn't listen very often.  With the current setup, she makes her own playlists and (especially for her favorite vocalists) will crank the volume (previous to my current setup that never happened).  All of that is to say that it may not be the characteristics of the amp.  

 

Personally, I have found that power conditioning (which depends upon your location and power delivery to the home) and cables can make a significant difference.

[fas42]

2 hours ago, Jud said:

Once again, why inexact trial and error with cables when you can achieve a much more exact and specific solution for your speakers and room with digital room equalization software? This works with not only frequency response but timing/phase (imaging, depth, soundstage) also.

 

Digital room equalization software is not a solution - it's a workaround, to help minimise the subjective irritation from the distortion in the sound coming from the speakers. Far better to reduce that distortion - which is, yes, "harder", and currently, effectively non measurable - as evidenced by all these reports of designers using listening to work out where they're at ....

[jaytor]

I've been following this recent discussion with some fascination. I've been an audiophile for close to 50 years, and was an electronics engineer in my early career (I've run a modest e-commerce business and developed web software for the past 20+ years).

 

In the last several years, I've become an avid DIYer - building a dozen or so amps, preamps and speakers. I do a lot of SPICE simulations and use test equipment (scope, distortion analyzer) during prototyping, but my final arbiter has always been listening.  

 

When I first started out as an audiophile, it was all about the measurements - these were the days of Julian Hirsch and his compatriots. But I soon discovered that I preferred the sound of equipment that was not always the best measuring. 

 

I am not a believer in the "Absolute Sound" as espoused by Harry Pearson, etc. I don't really care if the music sounds exactly the same as it did in the original recording venue. I want the music to move me. It's not an analytical response - it's an emotional one. I've often found that equipment that has the best "measurements" sounds, at best, boring, and, at worst, fatiguing. Some "distortion", whether it be frequency response variations or 2nd and 3rd harmonics, can be very pleasing to my ear, and make the music much more enjoyable. A lot of global feedback can often result in better measurements (particularly if you're just measuring THD and noise), but far worse sound.

 

In my DIY designs, I've found that different parts can make a big difference in my enjoyment in the music, even though they measure virtually the same. Since I'm not building my equipment to make a profit, I don't really care if the cost is justified on a pure price-performance curve. If I like the way it sounds, that's all that counts. For example, some of the copper foil in oil film caps sound a lot better to me than cheap film caps, let along electrolytics, yet they have very similar parameters (although electrolytic caps tend to have higher ESR and dieletric absorption). 

 

So, while I have a background in electrical engineering, I generally fall much more in the subjective camp than the objective one. I don't discount measurements - they are an invaluable tool for design and production, but, in my opinion, they are not the final arbiter in sound quality.

 

[mocenigo]

2 hours ago, PYP said:

Also, for the Kaluga amps, Kubala-Sosna cable was used to connect the PCB to binding posts.  Why?  Did it measure better?  Or sounded better and measured no worse?

 

There are many reasons for that. It may be that they know that the customers may expect audiophile cables and then they give the customers what they want. I am not saying that Bruno and Co do not believe in cables, but what they use themselves is rather mundane (like the cordial 425 as a speaker cable) and this means something.

 

 

2 hours ago, PYP said:

When one reads about respected designers who carefully choose certain capacitors, for example, the choice is stated not in terms of measured differences (which one assumes were used to narrow the choices, along with considerations of high rate of production meeting the design specifications, cost, availability, etc.) but preferred "presentation."

 

Capacitors are usually chosen for robustness and build quality. On “high end” products they are chosen according to customer expectations.

 

A difference in colour for instance implies a difference in frequency response - thus a measurable one. If the difference is tiny, then it disappears the moment the comparison is done blind. If the difference is large then either the value of the capacitor is slightly different or the cap is defective.

 

A good cap has constant ESR over large periods of time, stable capacitance, forms quickly, and is stable mechanically and does not pick signals from vibration. You do not need to go Duelund for that. The purple clarity caps are perfect.

 

2 hours ago, PYP said:

 

I'm certainly not advocating for designing by ear, nor making changes that measure worse.  But as Bruno has mentioned, sometimes listeners can hear noise (or choose a better word) that initial measurements missed (as @barrows noted).  

 

Aind note that this is exactly what I said: you identify (or believe to identify!l) an issue, you try to determine what measurements are correlated with that issue, then attempt to address that problem and you verify by ear whether you guessed correctly.

 

 

2 hours ago, PYP said:

 

He takes that as a challenge to find the measurements that identify the problem area.   Had he not done so, I don't think Class D would today be considered a topology that works for the high-end market.   He blazed the trail.  His work has greatly influenced Grimm Audio, Hypex, Mola Mola, Kii and Purifi.  

 

At any rate, I think there is more agreement than disagreement in how we perceive these issues.   

Absolutely! I actually think I am 99% in agreement with barrows, for instance.

 

But I want to stress that I firmly believe that everything we hear in a properly controlled setting can be measured. The problem may be to identify the right physical quantity to measure, but our ears are, frankly, crap, so anything we can ear should be easily measurable with standard equipment.

[fas42]

1 hour ago, jaytor said:

So, while I have a background in electrical engineering, I generally fall much more in the subjective camp than the objective one. I don't discount measurements - they are an invaluable tool for design and production, but, in my opinion, they are not the final arbiter in sound quality.

 

 

Your background is somewhat similar to mine - the normal measurements don't take account of what's important to the listening brain, and therefore you need to use other methods, to optimise.

 

Experiences along the way dictate the approach taken - very early on, I realised that interference and noise factors are absolutely critical to control, and digital sourced playback is the most sensitive, subjectively, to these aspects. I use very ordinary parts and materials, in things like cables, because I have learned how they need to be utilised, so that the 'quality' of them doesn't matter - exotic and pricey items can also do the job, but are unnecessary if the right approach is used.

[PYP]

2 hours ago, mocenigo said:

But I want to stress that I firmly believe that everything we hear in a properly controlled setting can be measured. The problem may be to identify the right physical quantity to measure, but our ears are, frankly, crap, so anything we can ear should be easily measurable with standard equipment.

I was nodding in agreement as I read your post until I got this the highlighted part.  Do you mean that gear can be designed that has better measurements than the ear can detect?  If so, what would be the point?  

 

[mocenigo]

5 hours ago, PYP said:

I was nodding in agreement as I read your post until I got this the highlighted part.  Do you mean that gear can be designed that has better measurements than the ear can detect?  If so, what would be the point?  

Well, this is already happening for many years, with DACs, and it started recently with amplifiers. I would say, bragging rights. You have a DAC with a THD+N (A) of 120Db, but I have the next iteration from the same company, with nearly the same circuit, and a THD+N (A) of 121Db. I win. Our ears have an internal distortion that is ludicrously higher, so any distortion level over about 100Db (and probably also much higher) cannot be discerned. Noise is covered by ambient noise except in an anecoic room, but the noise of your own circulatory system is already higher. 

[Matias]

On 5/24/2023 at 11:26 AM, barrows said:

I found the high frequencies are slightly more refined (more extended, and smoother) with Purifi vs Ncore-it is a small thing...  I wonder if Nilai has a similar improvement?

Can't say about the Purifi as I never heard one, but having recently upgraded from NC500 to NCx500 I definitely heard improvements in bass dynamics (kick drums and electric bass, when strong on the recording, are now extra strong), while also improved instruments definition and textures in the midrange. Can't say the treble was different, more like improved like the rest maybe? Anyway still very much recommended upgrading to NCoreX. Not a huge difference, but very worth it.

[PYP]

4 hours ago, mocenigo said:

Well, this is already happening for many years, with DACs, and it started recently with amplifiers. I would say, bragging rights. You have a DAC with a THD+N (A) of 120Db, but I have the next iteration from the same company, with nearly the same circuit, and a THD+N (A) of 121Db. I win. Our ears have an internal distortion that is ludicrously higher, so any distortion level over about 100Db (and probably also much higher) cannot be discerned. Noise is covered by ambient noise except in an anecoic room, but the noise of your own circulatory system is already higher. 

https://www.dailymail.co.uk/sciencetech/article-2124581/The-worlds-quietest-place-chamber-Orfield-Laboratories.html

 

The longest that anyone has survived in the ‘anechoic chamber’ at Orfield Laboratories in South Minneapolis is just 45 minutes.

 

"When it’s quiet, ears will adapt. The quieter the room, the more things you hear. You'll hear your heart beating, sometimes you can hear your lungs, hear your stomach gurgling loudly.

In the anechoic chamber, you become the sound."

[Jud]

14 hours ago, fas42 said:

 

Digital room equalization software is not a solution - it's a workaround, to help minimise the subjective irritation from the distortion in the sound coming from the speakers. Far better to reduce that distortion - which is, yes, "harder", and currently, effectively non measurable - as evidenced by all these reports of designers using listening to work out where they're at ....

 

So here are before and after measurements of the "effectively non measurable" distortion coming from speaker interactions with the room (before and after digital room equalization).

 

 

[Jud]

6 hours ago, mocenigo said:

Well, this is already happening for many years, with DACs, and it started recently with amplifiers. I would say, bragging rights. You have a DAC with a THD+N (A) of 120Db, but I have the next iteration from the same company, with nearly the same circuit, and a THD+N (A) of 121Db. I win. Our ears have an internal distortion that is ludicrously higher, so any distortion level over about 100Db (and probably also much higher) cannot be discerned. Noise is covered by ambient noise except in an anecoic room, but the noise of your own circulatory system is already higher. 

 

Interestingly, in the case of my former amp and its replacement, I did find an objective as well as subjective difference where I didn't expect one. With the old Class A amp, a very fine one (Spectral), when turning up the volume with no music playing I was able to hear a slight hiss from the tweeter and slight hum from the midrange and bass. With the Purifi-based Class D, whose distortion specs were lower than the already quite low ones of the Spectral, the same test produced dead silence.

[fas42]

8 hours ago, Jud said:

 

So here are before and after measurements of the "effectively non measurable" distortion coming from speaker interactions with the room (before and after digital room equalization).

 

 

 

I don't consider FR variations as being in the category of subjectively irritating; it's linear distortion versus non-linear - the latter is much harder to ignore when listening. In the waterfall graphs, you are seeing the very high levels of distortion that most drivers produce when asked to produce very low frequencies; these much higher frequency harmonics are very certainly audible, and do an excellent job of colouring what you hear - which is why subwoofers can add so much 'character' to the presentation, . So here, yes, taming the behaviour of the driver is helping, reining in excessive, highly inaccurate, low bass.

 

But this is the distortion associated with speaker drivers trying to do very low bass - not that of electronics circuitry ...

[fas42]

14 hours ago, mocenigo said:

Well, this is already happening for many years, with DACs, and it started recently with amplifiers. I would say, bragging rights. You have a DAC with a THD+N (A) of 120Db, but I have the next iteration from the same company, with nearly the same circuit, and a THD+N (A) of 121Db. I win. Our ears have an internal distortion that is ludicrously higher, so any distortion level over about 100Db (and probably also much higher) cannot be discerned. Noise is covered by ambient noise except in an anecoic room, but the noise of your own circulatory system is already higher. 

 

DACs have historically had a type of distortion which masks low level detail - used to be quite common to remark on how the sound would fall into a "black hole", and that decay tails of instrumental sounds would stop abruptly, not be realistic. I used to shake my head, years ago, at how hopeless the replay on CD systems typically was, on disks I knew  well - literally, half of what was going on, musically, just wasn't there.

 

Which was never measured. And still isn't.