[castleofargh]

Doesn't that then contradict the statement that gravity accelerates - at least after the point where the fall rate is achieved? What I mean is if gravity accelerates then the objects would continue to fall at a faster rate (accelerate) rather than plateauing at a speed in a vacuum. Didn't Newton have an equation for this?

oh now I get what your problem was. that they talk about acceleration while saying that the air friction would end up stabilizing the "fall" of the object to a constant speed(which means no acceleration). ^_^

 

[SilentNote]

Doesn't that then contradict the statement that gravity accelerates - at least after the point where the fall rate is achieved? What I mean is if gravity accelerates then the objects would continue to fall at a faster rate (accelerate) rather than plateauing at a speed in a vacuum. Didn't Newton have an equation for this?

Same rate as in same velocity between both objects. Not same rate as in constant velocity. The rate of change will be ~ -9.8 m/s^2. In other words, if it is now static, after one second the velocity will be at 9.8 m/s, the next second, at 19.6m/s so on and so forth, assuming there's no drag / buoyancy. Doesn't matter if it's a parachute or a small lead ball, they fall at the same velocity as they are subjected to the same gravitational acceleration (instantaneous rate of change). And you are right that in a vacuum it the object will continue to fall at a faster rate until it hits something.

If there is drag, then the acceleration is not the same for 2 objects with different air resistance, as the air resistance will reduce the total acceleration (usually until the drag = gravitational acceleration). At this point, the object will stop accelerating and fall at a constant speed.

 

[Dogmatrix]

When it comes to accepted hearing ranges, there is more variance with low frequencies. So the average of accepted studies say that the normal range for a healthy young adult is 20hz-20khz. Some studies have found the low is 16hz or 15hz, which I assume is environmental bone conduction. The only studies about humans hearing 100khz are deep sea divers...in which it’s direct conduction of water to middle ear and bone. When it comes to speech ranges, I would like to see your citation of how a given person hears above common speech ranges.

The point as I read it in the referenced studies is the subjects had the perception of hearing speech in the upper audible range ie 12-16khz but the speech was in fact being transmitted by bone conduction at 40khz in the case of the Lancet study and up to 108khz in the other .

 

[Dogmatrix]

no I'm saying that other people(including me) shared the same idea you got of using the same DAC model with the 2 boards. to try and reduce the extra variables by some amount. but it led nowhere in this topic at least. and I don't know if anybody since had both options at the same time and bothered running some blind tests.


I disagree right at the start. there is not a large body of experimental evidence suggesting that 2 DACs sound different. what we have is mostly a great many testimonies based on listening conditions(uncontrolled or very poorly controlled) that have no place in any serious research.
looking for ideas to explain an event is correct, but that should not come before we have properly confirmed that the event is real. with a typical sighted experience, we do not have a demonstration of audible difference. only a demonstration that some people feel like they heard a difference. and that to me is a big distinction. because the feeling of hearing a difference is also found in many tests where the subjects got tricked into thinking they were listening to 2 different DACs, while hearing only one output throughout the tests.

RE Schiit
Oh well
RE I disagree
The term is experiential evidence
"Much of the intuitive appeal of evidentialism results from conflating two importantly different conceptions of evidence . This is most clear in the case of perceptual justification , where experience is able to provide evidence...…….."
Lyons, J. Philos Stud (2016) 173: 1053. https://doi.org/10.1007/s11098-015-0540-z

 

[castleofargh]

RE Schiit
Oh well
RE I disagree
The term is experiential evidence
"Much of the intuitive appeal of evidentialism results from conflating two importantly different conceptions of evidence . This is most clear in the case of perceptual justification , where experience is able to provide evidence...…….."
Lyons, J. Philos Stud (2016) 173: 1053. https://doi.org/10.1007/s11098-015-0540-z

eheh, sorry, I thought it was typo ^_^. didn't know that word existed in English.
my position on listening test and what we should trust: if a difference is big and easily noticeable, then we don't need controlled tests to confirm it. but at the same time, if a difference is really big, it's going to be so trivial to demonstrate both its existence and audibility that I don't get why people wouldn't just do it and be done anytime they have the desire to demonstrate the fact. as for small differences, there are just too many reasons why we shouldn't trust a vague sighted impression to determine audibility.
with DACs, the usual level of fidelity makes it very likely to encounter small differences where that following type of recommendation should apply https://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.1116-3-201502-I!!PDF-E.pdf

 

[Dogmatrix]

eheh, sorry, I thought it was typo ^_^. didn't know that word existed in English.
my position on listening test and what we should trust: if a difference is big and easily noticeable, then we don't need controlled tests to confirm it. but at the same time, if a difference is really big, it's going to be so trivial to demonstrate both its existence and audibility that I don't get why people wouldn't just do it and be done anytime they have the desire to demonstrate the fact. as for small differences, there are just too many reasons why we shouldn't trust a vague sighted impression to determine audibility.
with DACs, the usual level of fidelity makes it very likely to encounter small differences where that following type of recommendation should apply https://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.1116-3-201502-I!!PDF-E.pdf

No worries it is obscure language but quite apt I thought .
I agree , I think weight of evidence is important and vague sighted impressions carry little weight but In large volume it adds up . Regardless of volume it of course lacks the credibility to carry the debate alone . So many place importance in small perceived difference I think it worth investigating .
I will have a look at the pdf tomorrow it is listening time down under , interesting the sub section is titled BS just saying .

 

[Steve999]

oh now I get what your problem was. that they talk about acceleration while saying that the air friction would end up stabilizing the "fall" of the object to a constant speed(which means no acceleration). ^_^

I am having one sticking point. Okay, you have two DACs. Very different masses, one one is quite expensive, one is cheap, one is multibit and one delta sigma, but somehow they have the same air resistance (coefficient of drag or whatever). @Bighshot receives them from New Zealand by flying pig in the mail on the West Coast of Hawaii from a guy named Larry and drives them over to you in Brooklyn, after he runs an extensive test with thousands of college students in conjunction with the faculty at Cal Tech and they both sound the same to everybody there as his $40 Walkman.

So you figure they are both garbage. You go to Brooklyn and drop them both straight down from the Tower of Pizza, which is even taller than the Seattle Sewing Needle. It is not a vacuum, even though the air is barely breathable. The rate of fall of both DACs increases at the same rate until the coefficient of drag settles the rate of fall down to an even 500 m/s. They hit the sidewalk at the same time and both are smashed to bits. A typical New Yorker finds them on the sidewalk and tries to sell them to unwitting tourists as spare UFO parts.

(True story, BTW.)

Now technically I am told gravity accelerated, not the DACs. And I verified it on the Internet so it must be true. I am figuring gravity itself has no coefficient of drag, whether we look at is as a force (Newton) or a warping of space-time (Einstein), and whether it’s caused by weightless undetectable gravitons or undetectable eleven-dimensional strings, or, just maybe, something else. It is the DACs themselves that are affected by the coefficient of drag, not gravity.

So did the gravity stop accelerating after the DACs settled down at 500 m/s? Or does the gravity keep accelerating even after the coefficient of drag has caused the rate of fall of the DACs to settle down to a constant rate 500 m/s?

 

[KeithEmo]

I would personally agree that "there's no such thing as agreeable distortion or noise"....

However, there are absolutely types of both that are less disagreeable to most people than others.
For example, assuming you have a noise floor that is low but still slightly audible, for the same S/N, many people find "analog hiss" like tape hiss much less annoying than digital quantization noise.
In some situations this may even extend to unequal amounts... for example, many tape fans cheerfully tolerate high levels of "harmless tape hiss", to avoid far lower, and barely audible, levels of digital artifacts that they find far more annoying.

An analogous situation exists with the latest h.265 video compression CODEC.
For a given measured "loss of quality" the new CODEC substitutes a rather innocuous softening for the unpleasant blocky artifacts produced by the previous h.264.
(The new CODEC does actually deliver better measured quality for a given level of compression... but, even when delivering the same measured level of quality, the flaws it contains are less visually unpleasant to most viewers.)

On the notion of manufacturing tolerances...
I understand what you're saying, and you are generally correct, but the details can sometimes be more complex, and the comparison between R2R and D-S still applies.

The thing you need to remember is that precision carefully matched parts are critical in some situations - yet deliver no benefit whatsoever in others.
For example, in a typical analog amplifier, certain pairs of components must be carefully matched, especially if you want good performance, while others perform perfectly even with considerable variation.
(It might be a nice idea to carefully sterilize your garden tools before planting flowers - but it offers no actual benefit at all.)

From a design and manufacturing perspective an R2R DAC requires precision matched components in order to deliver reasonably good performance.
Specifically, precision carefully matched ladder resistors are necessary in an R2R DAC.
Unless you use expensive, high precision, carefully matched resistors in the ladder network, it's performance will be audibly and measurably poor.
So, rather than reflecting "better manufacturing quality" they actually do represent "the cheapest part that will actually do the job even reasonably well".
(In engineering terms this is considered to be one of the drawbacks of the R2R topology... that it only performs at all well if you use expensive and carefully chosen parts.)
In contrast, a D-S DAC does NOT rely on a set of carefully matched resistors to deliver its linearity... so it can deliver similar or better performance without the requirement for those precision components.
This was in fact one of the major factors motivating the development of D-S DACs....
(And it's why D-S DACs have almost entirely replaced the older R2R topology for almost all audio applications.)

I point this out because the manufacturers of many R2R DACs are quite proud of the fact that they use expensive, precise, carefully matched resistors.
And they point this out in their marketing literature to suggest that their product is "a quality product" because it uses "expensive carefully chosen precision parts".
However, in engineering terms, what it suggests is that, due to inherent design issues, the R2R topology forces the manufacturer to use unnecessarily expensive components.
I've seen many ads that infer, or claim outright, that a D-S DAC that uses less precise components will necessarily not perform as well - which is simply untrue.
However, in the audiophile world, and a few other niche markets, people are too readily willing to believe that "if it's too cheap they must have cut an important corner somewhere"....

A reasonable analogy would be if my economy car required expensive aviation fuel - in order to deliver the same performance that its competitors delivered with plain old regular gas.
(And if the manufacturer were to advertise that "it must be faster and more powerful - because it burns more expensive higher quality fuel".)

Very good point , I had discounted shall we say agreeable distortion . Harmonic distortion in tube amplifiers would be another example . Not convinced on agreeable noise since I am a black background type but I would be open to consider noise as agreeable coloration perhaps .
Tolerance I was referring to was in fact the sourcing and testing of suitably matched resistors as opposed to manufacturing of the unit as a whole . I have some personal experience of this and know it is difficult to find manufacturers that use tight enough tolerance in the first place and mind numbingly tedious to test and match them (resistors not manufacturers).
I am well aware of the roll off character in nos dacs but would hesitate to say 20khz is audible certainly not in my case .

 

[KeithEmo]

Gravity actually applies a constant force...
The acceleration is the result of that force acting on a mass...
And, since the mass remains constant, the force will also remain constant...
However, terminal velocity will be reached when upward force applied by air friction is exactly equal and opposite to the force applied by gravity...
(Once the speed at which this occurs is reached, the system will be in equilibrium, and the parts will continue to fall at that rate... until the sidewalk intervenes.)

And, incidentally, assuming a proper location, and a steady supply of tourists, it is almost certain that those parts will in fact be sold...
(Although, being New York, it is more likely that they will be sold as "a fancy new Japanese wrist watch MP3 player"... )
(I'm also pretty sure the Tower of Pizza isn't in NY.... unless it's been sold recently. )

I am having one sticking point. Okay, you have two DACs. Very different masses, one one is quite expensive, one is cheap, one is multibit and one delta sigma, but somehow they have the same air resistance (coefficient of drag or whatever). @Bighshot receives them from New Zealand by flying pig in the mail on the West Coast of Hawaii from a guy named Larry and drives them over to you in Brooklyn, after he runs an extensive test with thousands of college students in conjunction with the faculty at Cal Tech and they both sound the same to everybody there as his $40 Walkman.

So you figure they are both garbage. You go to Brooklyn and drop them both straight down from the Tower of Pizza, which is even taller than the Seattle Sewing Needle. It is not a vacuum, even though the air is barely breathable. Both DACs accelerate at the same rate until the coefficient of drag settles the rate of fall down to an even 500 m/s. They hit the sidewalk at the same time and both are smashed to bits. A typical New Yorker finds them on the sidewalk and tries to sell them to unwitting tourists as spare UFO parts.

(True story, BTW.)

Now technically I am told gravity accelerated, not the DACs. And I verified it on the Internet so it must be true. I am figuring gravity itself has no coefficient of drag, whether we look at is as a force (Newton) or a warping of space-time (Einstein), and whether it’s caused by weightless undetectable gravitons or undetectable eleven-dimensional strings, or, just maybe, something else. It is the DACs themselves that are affected by the coefficient of drag, not gravity.

So did the gravity stop accelerating after the DACs settled down at 500 m/s? Or does the gravity keep accelerating even after the coefficient of drag has caused the rate of fall of the DACs to settle down to a constant rate 500 m/s?

 

[SilentNote]

So did the gravity stop accelerating after the DACs settled down at 500 m/s?

Nope, gravity still acts on the DACs even when they have reached terminal velocity.

Or does the gravity keep accelerating even after the coefficient of drag has caused the rate of fall of the DACs to settle down to a constant rate 500 m/s?

Gravity keeps accelerating at ~ -9.8m/s^2 and drag keeps doing the opposite until it reaches +9.8m/s^2. During the terminal velocity, -9.8m/s^2 + 9.8m/s^2 = 0 m/s^2, therefore no more change in velocity will occur to the DACs, the DACs will fall at a constant velocity of 500m/s (as per your example).

Actually the DACs and Earth attract and accelerate each other, but since one is massively larger than the other, it kinda gets ignored. The gravitational constant also changes depending on where you are on earth and your current altitude.

 

[KeithEmo]

The answer to your question: Why do we only measure amplifiers on the voltage side? is this....

Because, since a speaker is a passive load, the current that passes through it is directly related to the voltage that is applied to it. If you know the voltage, and you know the impedance of the speaker, then you already know (or can calculate) the current. They cannot be separated and so there is no specific reason to consider them separately.

Your statement further down is entirely correct - the mechanical drive force applied to a typical loudspeaker (excluding electrostatics and certain other exotic designs) is proportional to the current flowing through their voice coil. This would seem to suggest that we would get better performance if we controlled the drive current directly. (And it is in fact trivially simple to design a "current drive amplifier" - whose output current, rather than its output voltage, is proportional to its input voltage.)

The "catch" is that, since all commercial amplifiers are "voltage output" amplifiers, existing speakers are designed with that in mind... and would have to be altered to work well with the other type. For example, a typical dynamic loudspeaker has at least one mechanical resonance which depends on both the driver and the cabinet. At that frequency, both its electrical impedance and its mechanical acoustic efficiency rise. When driven by a voltage drive amplifier, the rise in impedance results in the speaker drawing less current, which tends to partially counteract the rise in acoustic efficiency. However, with a current drive amplifier, the current would remain constant, and, as a result, the rise in mechanical efficiency would result in a major peak in output at that frequency. (It would certainly be possible to design speakers that would work well with a current output amplifier... but it's doubtful that existing available models would.)

The main reason for the existing disparity between "amplifiers that have similar output voltage capabilities but different current capabilities" is due to how we measure amplifiers. We typically measure amplifiers using a resistive load - even though this is not at all characteristic of most loudspeakers - most of which offer a very reactive and often very complex load. Therefore, many amplifiers which can deliver the current required to sustain their specified output voltage into a resistive load, are unable to do so into many commonly encountered real world speaker loads. So they measure one way when connected to a resistor and quite differently when connected to different speakers. (However, if you measure the output voltage WHILE THE AMPLIFIER IS CONNECTED TO A GIVEN SPEAKER OR OTHER LOAD, the current will always be directly related to the voltage, so there is no need to measure or respond to both separately.... and you cannot in fact separate the two. For a given load, and a given voltage, there is only one possible current.)

Of course, in any given design, it is perfectly reasonable to actively reference either the output current or the output voltage to the input voltage... but the two will always be directly related to each other. (You cannot have two amplifiers that, with the same input signal, and the same load, actually deliver the same output voltage, but different output currents, or vice versa... it is simply not possible.)

(If a certain amplifier were to try to deliver a certain voltage, yet be unable to source or sink the appropriate amount of current necessary to do so, then it would be unable to deliver the correct voltage, and the disparity would show up in the voltage measurement.)

I am not going to enter into a tit-for-tat with you, because I believe that is what you want. I don't care whether you are right or wrong. It has no benefit to me. I am not on any crusade and it strikes me that you are. That is not my role.

Now I don't have your ears, I cannot replicate what you have there and what you did or did not do. I have not seen you conduct any of your 'blind tests' and hence I shall not comment, whether I approve of your methodology or not, that does not interest me.

So what interests me?

Doing my job!

You are certainly invited (as anybody is) to come here and listen to Beethoven. I am a cordial and always polite host, I never raise my voice.

BTW, I know about the Stereo Review magazine. That was 32 years ago and if you are doing the same as they are, then I am not surprised. We have thankfully come a long way since then. I have been involved in amplifier design for fourty years and if you cannot come up with a blind test that shows an improvement since then or even 1987? If that is the kind of results you come up with, then I am wasting my time.

Most amplifiers still don't sound that good anyway.

I believe we are on the cusp of coming out with a new generation of amplifiers, they measure well but not ultra-low distortion and they are totally different to anything on the market.

QUESTION: Why do we only measure amplifiers on the voltage side?

For example, we are only now starting to understand that we have been using a "voltage" model and never really measuring the distortion on the current side. It turns out that there is a correlation between amplifiers, what they do on the current side has hardly been looked at, but amplifiers that have been accepted as sounding good also do better on the current side.

The coil in the loudspeaker responds to current, not voltage.

Measurement shows that a single amplifier can have two different distortion profiles, one on the voltage side and a completely different one on the current side. Which one are we listening to? If you are listening to dynamic speakers, then the uncomfortable thought is that it must be the current distortion profile.

Measure the distortion on the current side and do something about it? Then we have a different beast. This is happening here in Australia right now. Do these amplifiers sound different? Oh yes, you bet!

PS: No, these amplifiers are not current sources and we are not talking about so-called current driving.

 

[KeithEmo]

I absolutely agree.

As far as I know, there is no "large body of scientific evidence" that R2R and D-S DACs sound significantly different...
However, there is also no "large body of scientific evidence" that they do not...
And the admittedly large body of unscientific and anecdotal evidence seems to be somewhat evenly divided...
(Just for the record - in the few cases where I heard clearly audible differences they could be attributed to obvious measured differences in frequency response.)

As far as I know no such large scale tests have even been conducted (or, if they have, they weren't published)...
Therefore, all we have are some default assumptions...
(And, while many of those default assumptions are inferred from reasonably reliable data, how well that data correlates to the current question has also not been conclusively shown.)
However, some people who are quite convinced that their particular default assumptions are "obviously the most likely to be correct"...
And those folks repeatedly claim that, based on that assumption, any claim to the contrary is "exceptional and requires exceptional proof"...

I should point out that admitting that there is no proof either way does NOT constitute "conceding that the anecdotal claims are true"....

All you are saying is that YOU have not heard any difference. But YOU have adopted an attitude where you now expect no difference. So are YOU not also guilty of the same thing? You have already made up your own mind.

Come here and I will show you that there are dramatic differences in DACs. You won't own them, so no bias there, and you won't know the price either, again no bias. In fact, bring your own DAC and we shall play that first and then we put in another that I have here, not crazy money, YOU now listen and YOU WILL HEAR A DIFFERENCE!

This challenge is OPEN to EVERYONE!

But please understand the logistic limits. Even blind tests have limits, but let's face it, for that reason they are costly to conduct. People like YOU have already made up your mind, so will YOU come up with the dosh to pay for it? No, because YOU have already made up your mind, SO NO PAY!

So for my challenge, it too is OPEN to EVERYONE.

The logistic limit is, they have to COME HERE.

At least some, often MANY have to travel to conduct a blind test, so please don't complain.

Above all:

HAVE AN OPEN MIND!

(Not shouting, capitals only for emphasis).

Joe R.

 

[bigshot]

Perception of audible is possible outside of accepted audible limits

You have a contradiction in terms there... How can inaudible be audible?

The thresholds of audibility are established by scientific testing to determine if the human ear can hear it. If it is inaudible, it's inaudible. Human ears have varying levels of degradation, but there is an upper limit to human hearing that no one can hear beyond.

The problem is that the average audiophile knows a great deal about specs in theory, but they know almost nothing about what those numbers on the page actually sound like. They assume because one amp has better specs than another, that there must be an audible difference. If the difference exists beyond human ability to hear, there is no difference. You're more likely to find that the difference is due to simple perceptual error or bias than it is actual sound. That's when you do a controlled test (line level matched, direct A/B switched, blind) to see if an audible difference exists. If you can hear a difference without controls, but not with controls the difference is because of the lack of controls, not the way the component actually sounds.

The studies that have shown perception of super audible sounds just show changes in brain waves. That doesn't mean that they are being heard. Sticking someone with a pin will result in a brain wave change. So will lying down rather than sitting up. There have been studies where music with super audible frequencies was compared to music without and listeners expressed absolutely no preference of one over the other. Inaudible frequencies were determined to add nothing to the perceived sound quality of music.

This argument usually is a last ditch effort for audiophiles to justify their biased perception. It's kind of like arguing about darker than pitch black or louder than deafening or hotter than scalding. Yes, all of that exists, but it doesn't matter because our ability to discern isn't infinite. The problem is normal human limits, not the quality of one amp over another.

 

[KeithEmo]

The problem here is that now YOU are being pedantic.....
Specifically, you are choosing a very narrow definition of "hearing" as opposed to "audible perception".....

There is an answer to your question:
"How can inaudible be audible?"

That answer is simply that there is no such definitive fact as:
"Certain sounds are inaudible."
There are ALWAYS conditions that must accompany any such conclusion.

In this case....
"When human subjects were tested, with steady state sine waves, using test tones limited to safe listening levels, the range of frequencies found to be audible to a typical human being was found to be limited to approximately 20 Hz to 20 kHz." (Although recent tests strongly suggest we should extend that range downwards to 10 Hz.)

You continually insist that "the thresholds of audibility are established by scientific testing" - and I would assume that includes an "upper limit" of about 20 kHz.
Yet, in general, all of those test results have been limited to very specific conditions.
Yet someone else published a reference to an experiment where it was shown that, when subjected to frequencies in the 40 kHz range, subjects PERCEIVED hearing a sound.
So, apparently, under some conditions, a 40 kHz tone produces a response which the subject experiences as hearing a sound.
So, under those specific conditions, apparently a 40 kHz tone, or the presence of a 40 kHz tone, is in fact audible after all.
This would certainly seem to open the door to all sorts of interesting "audible interactions" that you simply choose to ignore.

For example, assuming we had two otherwise identical DACs, but one delivered occasional bursts of ringing at 40 kHz...
And I were to listen to both, using electrostatic headphones, which have useful response to 40 kHz...
Since the headphones are clamped onto my head, I might reasonably expect some of that sound to reach my inner ear via bone conduction.
And, according to the results of that experiment, I would expect those 40 kHz noise bursts to "produce an audible impression of hearing a sound".
And, because that sound would only be present with one of the two DACs, I would expect to "perceive an audible difference" between the DACs...
However, the question could probably be answered with better surety if anyone were to actually bother to run the experiment.

I don't disagree with you that, in many cases, and perhaps even a majority, a lot of what audiophiles claim to hear or believe they hear is nonexistent.
However, I find it totally unreasonable to claim that this applies to EVERY case.
You would also have to bang a lot of metal blocks together before you find the ones that set off a nuclear explosion when you do so...
However, if you claim that "you can't EVER cause a nuclear explosion by banging two blocks of metal together, you will still be incorrect.

The problem, as I see it, is that your statement about "applying controls" in inaccurate and overreaching.
In fact, if you can hear a difference without controls, but not with controls, then the difference MAY HAVE BEEN because of the lack of controls.
However, it is also possible that your controls were poorly chosen, and have actually obscured a legitimate difference, which might be obvious under other conditions.
(For example, you can virtually ensure that all DACs will sound the same, by the simple expedient of comparing them using a 1950's vintage carbon telephone speaker.)
The problem is that you continually refuse to admit this possibility.

You have a contradiction in terms there... How can inaudible be audible?

The thresholds of audibility are established by scientific testing to determine if the human ear can hear it. If it is inaudible, it's inaudible. Human ears have varying levels of degradation, but there is an upper limit to human hearing that no one can hear beyond.

The problem is that the average audiophile knows a great deal about specs in theory, but they know almost nothing about what those numbers on the page actually sound like. They assume because one amp has better specs than another, that there must be an audible difference. If the difference exists beyond human ability to hear, there is no difference. You're more likely to find that the difference is due to simple perceptual error or bias than it is actual sound. That's when you do a controlled test (line level matched, direct A/B switched, blind) to see if an audible difference exists. If you can hear a difference without controls, but not with controls the difference is because of the lack of controls, not the way the component actually sounds.

The studies that have shown perception of super audible sounds just show changes in brain waves. That doesn't mean that they are being heard. Sticking someone with a pin will result in a brain wave change. So will lying down rather than sitting up. There have been studies where music with super audible frequencies was compared to music without and listeners expressed absolutely no preference of one over the other. Inaudible frequencies were determined to add nothing to the perceived sound quality of music.

This argument usually is a last ditch effort for audiophiles to justify their biased perception. It's kind of like arguing about darker than pitch black or louder than deafening or hotter than scalding. Yes, all of that exists, but it doesn't matter because our ability to discern isn't infinite. The problem is normal human limits, not the quality of one amp over another.

 

[Steve999]