Conclusive "Proof" that higher resolution audio sounds different

[Orb]

Just to add a more in general consideration that fits with IM or hirez/wide-bandwidth.
One needs to appreciate just in the same way with CD vs hirez players not all components (also critically meaning components such as opamps) are designed for playback or linear behaviour of wide-bandwidth as their scope (or design focus) of use would be for "standard CD quality" or lower.

Appreciate this is sort of stating "the bleeding obvious" but just thought I would mention it
Cheers
Orb

 

[Orb]

The last 4.1 seconds of both files should sound the same: 1 second of a low 4 KHz test tone, a click, silence, a click, silence, a click silence, and a click and 0.1 seconds of silence. If this area does not sound the same in both files, the probable cause is audible IM in your monitoring path.

Arny,
just on this point I would prefer measurements over subjective listening; especially as we have 2 standards in place and they are used by manufacturers.
Especially as they (all manufacturer types including those of opamps) usually go with SMPTE/DIN; the 60hz+7khz in a 4:1 ratio.

Just mentioning because you creating test sub 20khz, when we have objective standardised factual measurements available and this should be people's first point of interest IMO, or they can find the SMPTE files online to listen to.
Hang on, my memory bells ringing; has this been discussed by some in the past? - Caveat hot weather and I am one of the trolls out of Terry Pratchett's Discworld; need icecubes on my head to get it working properly in this heat

Thanks
Orb

 

[arnyk]

Oh I really do understand how it works Arny, btw most of the tests proposed into looking at IM forget musical content (putting keys to the side) is at least 40db-70db lower at ultrasonic levels, this is further compounded that IM will be at least 60-80db lower in sub 20khz region for a good product.

I don't think that how IM works is much of a mystery to those who are technically well-informed. But, for the average audiophile...

I find it hard to believe that so much equipment has been indicted by my little test for HF IM, but the facts are the facts. For instance, the PC I'm using right now passes the test. It uses an Asus Xonar DG audio interface (net price about $30), and the headphones are Superlux HD 668 the infamous Beyer DT 990 clones (net price $40).

The justification for the severity of the IM test that is included with the Keys Jangling file is that the Jangling Keys file itself is itself so severely composed of ultrasonics.

Here's a spectral analysis of the Keys Jangling file:



As you can see, it is highly atypical.

The background for this file is that I intended it to be a training file for some ABX sample rate tests involving more typical music, some 14 years ago. Things we
nt cattywumpus when a file this severe stumped my listening panel, and apparently the 100's or 1,000s of people who downloaded from my old www.pcabx.com web site. There were no, zilch, zip reports of reliable detection at the time and for 3-5 years thereafter until I took the site down. I have posted it infrequently since then, and no change.

Another aspect compounding this is to hear the sub 20khz IM one has to really turn the volume up, so hence you are now seriously stress testing an amp that has near full ultrasonic energy while the IM spectra amplitude is much lower than even normal music (again lets take keys out of this for now).

Modern amps should have no problem with these files. I'm worried about people going wild with their volume controls and taking out some tweeters. There are reports of AVRs going into protect mode due to enthusiastic playing of these files.

Everyone I have read on various forums using that test had to turn up the volume really loud; meaning they are seriously stress testing/or clipping the amp/or pushing it into non-linear behaviour due to the high crest factor-energy difference between audible sub 20khz and the extreme ultrasonic tones (usually close to or at 0dbfs).

The purpose of the test tones is to identify substandard monitoring chains and the people who are abusing good ones. Amir has been lavish with heaping criticism on my current hearing abilities, but if I use a monitoring chain that fails with the test tones, even I can reliably hear a difference with the Keys Jangling file.

BTW which product headphone amp failed your measurements and are those measurements on the web; am seriously interested to know.

Palindromic brand name should be a big hint! ;-) You oppo(sic) be able to figure it out! I don't recall if it was a 103 or 105.

Furthermore did that headphone pass the 19+20khz standard when pushed to same limit as higher tones therefore extreme loud volumes?

Send me an Oppo 105 and I'll test it! ;-)

The tests you do seem (I appreciate IMO) to comply with Dr David Griesinger conclusions that to hear IMD caused by ultrasonics even from keys one has to push a good/well designed product into clipping/non-linear behaviour.

Yes, even the best equipment will fail my test tones and show spurious audible differences if pushed into clipping. This program material is highly atypical in the interest of obtaining a positive result at almost any cost.

As I showed earlier with the Asus integrated DAC-Headphone it has exceptional low IM measurements (albeit using organisation international standards test measurement for IM rather than ones proprosed on forums).

One of the surprises is that some equipment will fail with some test tone pairs, and not others. They way they fail is also inconsistent with failures being either the generation of a spurious but fairly pure 4 KHz tone, or generation of a nasty sounding rather impure 4 KHz tone, or something else such as random sounding noise or squiggly sounds, or all of the above. Furthermore, IM has been traced to both electronics and transducers.

Asus is a good example to use because they are one of the worlds largest PC component manufacturers out there including critically motherboards with integrated audio/lan/usb/etc.

I think that many know that my day job is as a developer, builder, installer and servicer of PC-based system ranging from laptops to high performance desktops, to LANs I've been using and recommending primarily Asus products for over 2 decades. This policy has hurt my business because of their reliability. I was just repairing a LA where all the Asus-powered desktops and server had been in daily service for over 12 years, and other than the minor failures I addressed (primarily with the LAN wiring after a new phone system was installed).

Just to add though, should be noted Amir and maybe a couple of others (appreciate again not conclusive from a mass test but one meaning some seem to be identifying differences that were not meant to exist so one has to look at more than just IM) also did the ABX with music, which one would have to accept would not have the unusual ultrasonic amplitude/energy such as jangling keys or near 0dbfs dual ultrasonic tones.

Right. But when many try and only one seems to succeed, you don't have a new global rule, you have cause for more investigation.

While we cannot say this for all, we do know Amir mentions he did playback closer to normal listening levels than extreme loud/stress test component level.

Edit:
Just to add, I am not categorically saying IM is not the cause, but it is very unlikely compared to other possibilities and especially if those doing the ABX are using well designed products and listening in a way to not push components into clipping or non-linear behaviour.

For the record, no test of the Keys Jangling file is valid unless the test tones at the end of the file have been also tested without changing any volume control settings. The correct files may be downloaded from this URL: https://www.dropbox.com/s/ylrjezd7vc11leo/keys jangling with test tones.zip and only this URL. All other files and all other testing procedures are invalid.

 

[arnyk]

Arny,
just on this point I would prefer measurements over subjective listening; especially as we have 2 standards in place and they are used by manufacturers.
Especially as they (all manufacturer types including those of opamps) usually go with SMPTE/DIN; the 60hz+7khz in a 4:1 ratio.

Neither of those tests relate to the ultrasonic behavior of audio gear. If we are going be using sources that are capable of wide dynamic range > 20 KHz then testing that mode of operation seems relevant.

Even in the small number of files that have been analyzed, significant spurious tones > 30 KHz have been found. Their presence is easy to explain as well still have a lot of equipment with switchmode power supplies operating at frequencies that low.

Just mentioning because you creating test sub 20khz, when we have objective standardised factual measurements available and this should be people's first point of interest IMO, or they can find the SMPTE files online to listen to.

I have already encountered a surprisingly high percentage of people who have listened to my keys jangling files and for the first time discovered that their monitoring systems had audible nonlinearity.

I don't think that audio electronics has generally improved that much since Y2K when it comes to spurious responses that have enough amplitude to be clearly audible. For example most people are building their class AB power amps and preamps with the same power transistors and ICs as they were using back then.

And The Oppo BD player that someone caught misbehaving with my files was a pretty new design.

 

[Orb]

Arny,
your making me face palm with your insults (post 224), I really do know how it works thanks as used testing gear myself in the past; specifically multiple aspects involved as it is applicable for both digital and analogue.
Even if I did not it is made pretty clear by by Dr David Griesinger.....
His presentation has been linked several times first by JKeny and then me, which includes his own analysis (with spectral analysis) and IM test involving jangling keys and also going on to record musical instruments in same way.
First, I said lets keep the keys out of it to begin with in my post due to its unusual spectra behaviour, later on I pointed out Amir and it seems a couple of others did the test with music as well and then used part of that to also point out the IMD components should be substantially lower anyway than the fundamental even for jangling keys (hence why volume needs turning up even if one removed the real sub 20khz content so ensure no masking of IMD, or as people are finding out on forums they need to really turn up volume to hear IMD from ultrasonic test tones).
Anyway I suggest going back and read David Griesinger presentation and analysis-conclusions even using keys, which btw his spectrum looks much different to yours.

But answer me this, what amplitude is the IM spectra you found in the sub 20khz region in comparison to the ultrasonic even for keys?
Coming back to your card; are you saying it "passes" 19+20khz test but fails with ultrasonic; by fail I assume you mean the IMD is like less than 40db lower or something, or are you using subjective test, and what was the volume?
Just worth noting the $30ish Asus DG (meant to be able to support 96khz natively but would like to see it tested) is a stripped down version of the Xense (which supports 192khz), the DG uses lesser headphone amp (TI seem to only provide IM standards for the Xense and not amp component used in DG), lesser audio chip, and lesser DAC.

Not going to comment about the rest as I have put forward a lot already, which I still stand by; those tests are stress testing and causing non-linear behaviour in the electronics/not a reflection of real world listening as the IMD needs to be cranked up to be audible so like a recording being on average at -70dbfs or quieter for peaks, and this is not what listening tests should be; same way JA uses the 19+20khz at specific watts to see how an amp copes under seriously abnormal stress.
Regarding Asus, yeah only their higher range products are actually worth it IMO in terms of build and specification; unfortunately this is a moderate price jump from entry-budget priced cards/motherboards to their performance products.

Edit:
The key point as always; well designed-engineered product.
After all that saying has been used in various other ABX studies including power amplifiers/DACs/etc.
Cheers
Orb

 

[amirm]

First you might want to find someone else who can duplicate your work, Amir.

Good morning Arny. I don't recall anyone duplicating Meyer and Moran tests. Do you?

Who duplicated your amplifier test?

As you know, others have duplicated a subset of my results. Or else there would not be so much attention on them.

Getting someone else well known to proctor the test might be a good idea, too.

Sure. A lot of things are good ideas. But the biggest good idea is following international standards such as ITU BS1116 which says how important training/trained listeners are.

I'd say write that paper, and watch the AES review board make the identical same comments. ;-)

Got it.

(1) The basic technique and recordings involved have been around for 14 years or more and downloaded and tried by 100s if not thousands of people. No exceptional results have come forward until now.

Since we don't have any proctors verifying that, per above, I hope you don't mind us ignoring the data point.

(2) Speaking of technique, if memory serves you used Foobar2000 as your music player after ripping its design and ease of use a new termination for its digestive system.

I have made no comments about Foobar as a "music player." I have however explained in detail all of its failings when it comes to its ABX plug-in. That I can tell the differences still, shows the relative ease with which these differences are audible to my ears.

(3) A number of other people have tried to duplicate your results, but when an monitoring system IM test was added, their results fell out of the story.

I have read every post in the AVS thread and nothing remotely like this has happened Arny. You have made the claim alright but so far, you have not provided any shred of evidence that people achieved positive results due to "IM distortion" or any other such theory.

Remember, your IM distortion tests *were sighted* per your recommendation. And self reported with no proctor and no independent person per your points above. And that you yourself can't hear what we can hear. How can you counter the results of double blind tests run precisely as you said should be run?

 

[Orb]

Neither of those tests relate to the ultrasonic behavior of audio gear. If we are going be using sources that are capable of wide dynamic range > 20 KHz then testing that mode of operation seems relevant.

Even in the small number of files that have been analyzed, significant spurious tones > 30 KHz have been found. Their presence is easy to explain as well still have a lot of equipment with switchmode power supplies operating at frequencies that low.



I have already encountered a surprisingly high percentage of people who have listened to my keys jangling files and for the first time discovered that their monitoring systems had audible nonlinearity.

I don't think that audio electronics has generally improved that much since Y2K when it comes to spurious responses that have enough amplitude to be clearly audible. For example most people are building their class AB power amps and preamps with the same power transistors and ICs as they were using back then.

And The Oppo BD player that someone caught misbehaving with my files was a pretty new design.

I was responding to your comment of including 4 KHz test tone and end of the file for subjective hearing of IM; sorry if I misunderstood the context, the SMTE one I mentioned already exists.
I have not looked too closely at this site but they offer test signals (I do not like the fact mp3 but hey thats me) : http://www.audiocheck.net/testtones_imd.php
Again they stuck with an international standard, which is similar in terms of being under 10khz like your 4khz suggestion.

Would be interested in the link regarding the oppo test (appreciate might not be possible as you cover a lot of different threads and forums).
Part of the challenge though Arny is that there are global test standards for a reason, including the two used for IMD; it is difficult to say X (IMD) is not good enough due to complexity of music but the rest are fine (ignoring simple FR).

This is further compounded when you state the following:

One of the surprises is that some equipment will fail with some test tone pairs, and not others. They way they fail is also inconsistent with failures being either the generation of a spurious but fairly pure 4 KHz tone, or generation of a nasty sounding rather impure 4 KHz tone, or something else such as random sounding noise or squiggly sounds, or all of the above. Furthermore, IM has been traced to both electronics and transducers.

Therefore nearly all tests looking at non-linear behaviour are not good enough when it comes to music.....
But do you have a very specific example where a product has failed two tone test at mid-range frequencies and yet pass at other mid-range ones, and in both examples not pushed into behaving nonlinear?

Thanks
Orb

 

[amirm]

The justification for the severity of the IM test that is included with the Keys Jangling file is that the Jangling Keys file itself is itself so severely composed of ultrasonics.

Again, remember Arny that I also passed Scott/Mark's tests which were real music.

The background for this file is that I intended it to be a training file for some ABX sample rate tests involving more typical music, some 14 years ago. Things we
nt cattywumpus when a file this severe stumped my listening panel, and apparently the 100's or 1,000s of people who downloaded from my old www.pcabx.com web site. There were no, zilch, zip reports of reliable detection at the time and for 3-5 years thereafter until I took the site down. I have posted it infrequently since then, and no change.

Well, you now have the change . Please remember that these types of small distortions are either a) not audible to average person or b) they don't care to investigate if they are there. They will play one song and the other and if they sound similar at first blush immediately give up.

What happened on AVS was that once I showed clear differential, that motivated others like Mark to take it seriously and on his second try he found the difference solidly and reliably.

The purpose of the test tones is to identify substandard monitoring chains and the people who are abusing good ones. Amir has been lavish with heaping criticism on my current hearing abilities, but if I use a monitoring chain that fails with the test tones, even I can reliably hear a difference with the Keys Jangling file.

And I have shown that my equipment doesn't suffer from any such problem. So the fact that you hear it because your system is not as performant is not diagnostic relative to the discussion at hand.

Yes, even the best equipment will fail my test tones and show spurious audible differences if pushed into clipping. This program material is highly atypical in the interest of obtaining a positive result at almost any cost.

Which is very easy to do with your ultrasonic test tones as you made them at almost full amplitude. Here is the amplitude of the waveforms:

On the left are the key jingling sound as recorded. On the right, the packed waveform are the ultrasonic tones you added to the tail end. You see how high the amplitude is for the first segment? Even the highest amplitude peaks in the key jingling section doesn't match it let alone have it stay at level for so long.

For the record, no test of the Keys Jangling file is valid unless the test tones at the end of the file have been also tested without changing any volume control settings. The correct files may be downloaded from this URL: https://www.dropbox.com/s/ylrjezd7vc11leo/keys jangling with test tones.zip and only this URL. All other files and all other testing procedures are invalid.

The above waveform is from this latest set of files.

If I just get the amplitude stats for the key jingling part, it averages out to -34 dbFS.

If I scan the first set of ultrasonic tones, it is at -6 db or so.

That means there is a whopping 30 db or so difference in loudness.

You say that the volume must remain the same. So if I boost the key jingling so that it is closer to reference, the ultrasonics will surely clip. That clipping has nothing to do with "IM distortion" when playing back the key jingling section. That section did not have -6 db average volume level.

I have a lot more to say about your IM tests Arny . But for now, we can see how the test conditions are now being rigged to generate false results.

 

[Stereoeditor]

A number of other people have tried to duplicate your results, but when an monitoring system IM test was added, their results fell out of the story.

I have read every post in the AVS thread and nothing remotely like this has happened Arny. You have made the claim alright but so far, you have not provided any shred of evidence that people achieved positive results due to "IM distortion" or any other such theory.

At least Arny Krueger has now admitted, earlier in this thread that he was wrong to have publicly accused me 15 years ago as being an "ex-car mechanic with no formal education in audio engineering" (though his apology was somewhat ambiguously worded).

Perhaps in another 15 years, Mr. Krueger will admit that he was wrong about your ABX results, Amir.

I promised Orb I would post some plots of intermodulation (or lack thereof) of some D/A headphone amplifiers using Arny Krueger's choice of ultrasonic tones. I will do so, most likely tomorrow.

John Atkinson
Editor, Stereophile

 

[amirm]

A side note guys. Since running these tests I saw my lightning fast laptop come to a crawl. This is a core i7 laptop with 16 gigabytes of memory by the way and discrete graphics.

Anyway, I looked at perfmon and the problem was right there:

See it? Look at the memory usage of audiodg.exe. It has climbed up to over 13 gigabytes! Worse yet, it was leaking memory fast with the counter running like there was no tomorrow. So the CPU usage is also impacted.

Audiodg is the audio filter graph user process. It is triggered by running Foobar. Once there, it hits on a memory leak bug causing the runaway condition above. You would need to manually kill the process and restart foobar every time you want to use the latter to run these tests. Otherwise, in span of a couple of hours this morning it had already gobbled up more than 2 gigabytes! This is on Windows 7. Maybe fixed in Windows 8.

 

[Orb]

I thought only Microsoft made apps with memory leakage/not releasing allocated memory
Only kidding...
...
...
They arent the only ones hehehe

Cheers
Orb

 

[Orb]

To see how David Griesinger recording for his rattling keys compared to another hirez recording I looked at James Boyk's article (ignoring claims of what is/not audible and focused on recording-measurement).
Interestingly there is a reasonable (of course far from exact and compounded by scale used) correlation between both of theirs, however I may be missing something but they diverge from Arny's a fair bit, whether this matters or not in the scheme of things *shrug*.
They are page 14/15 in Griesinger's presentation and here for Boyk: http://www.cco.caltech.edu/~boyk/spectra/15.htm

Griesinger's presentation for those with PPT: http://www.davidgriesinger.com/intermod.ppt
Griesinger's presentation for those without - think link will work: http://view.officeapps.live.com/op/view.aspx?src=http://www.davidgriesinger.com/intermod.ppt
Thanks
Orb

 

[amirm]

I thought only Microsoft made apps with memory leakage/not releasing allocated memory
Only kidding...
...
...
They arent the only ones hehehe

Cheers
Orb

TO be clear, the bug is in Microsoft software. It is just that Foobar uses that subsystem and other players like WMP do not.

 

[Orb]

TO be clear, the bug is in Microsoft software. It is just that Foobar uses that subsystem and other players like WMP do not.

Bah your ruining my fun
Cheers
Orb

 

[esldude]

You know as I was creating this last test I did think about effect of dither. Due to shortness of time, I just did that one conversion with TPDF. As time permits, I will repeat without dither.

John, did I read an article from you in stereophile that adding dither to a 24-bit subjectively reduced fidelity?

Amirm,

You also could convert from 96/24 to 44/24 and see if the bit depth is more an issue than sample rate.

 

[Phelonious Ponk]

Sorry to interrupt, but most of this technical discussion is over my head, but I'm very interested to know if anyone, here or elsewhere, has duplicated Amir's results. I can't hear this stuff; never can. It would be good to know that's normal, not a personal defect.

Tim

 

[arnyk]

Arny,
your making me face palm with your insults (post 224), I really do know how it works thanks as used testing gear myself in the past; specifically multiple aspects involved as it is applicable for both digital and analogue.
Even if I did not it is made pretty clear by by Dr David Griesinger.....
His presentation has been linked several times first by JKeny and then me, which includes his own analysis (with spectral analysis) and IM test involving jangling keys and also going on to record musical instruments in same way.
First, I said lets keep the keys out of it to begin with in my post due to its unusual spectra behaviour, later on I pointed out Amir and it seems a couple of others did the test with music as well and then used part of that to also point out the IMD components should be substantially lower anyway than the fundamental even for jangling keys (hence why volume needs turning up even if one removed the real sub 20khz content so ensure no masking of IMD, or as people are finding out on forums they need to really turn up volume to hear IMD from ultrasonic test tones).
Anyway I suggest going back and read David Griesinger presentation and analysis-conclusions even using keys, which btw his spectrum looks much different to yours.

I'm familiar with that particular presentation and have cited it myself many times. Pleas notice that it is dated 2003 which is about 3 years after I first posted my Jangling Keys file on my own web site. Just as soon as I saw it mentioned here I went back and reviewed it one more time. He duplicated my procedures which were on the web at the time pretty carefully, and duplicated my results. I don't disagree with his stuff and I don't see his stuff as disagreeing with mine. I'm not accusing him of stealing my idea because my idea was very consistent with accepted professional practice and knowledge at the time and for decades before it. I first saw keys jangling used as a source of test signals in the late 1970s, if memory serves.

But answer me this, what amplitude is the IM spectra you found in the sub 20khz region in comparison to the ultrasonic even for keys?

I can predict it and even have simulated it, as well as measured it for real world equipment. It all depends on the equipment being used and the actual listening levels. However, since the stimulus is always ultrasonic, and much of the spurious responses are in a range where the ear is very sensitive, the responses are always more audible than the stimulus.

I mentioned that I think I have a case where it is very audible but not present in the electrical output of the sound card. I think the spurious response is > 2%.

Coming back to your card; are you saying it "passes" 19+20khz test but fails with ultrasonic; by fail I assume you mean the IMD is like less than 40db lower or something, or are you using subjective test, and what was the volume?

The failure was with the subjective test. So far I have measured the output of the card at the headphone jack and find reasonably low distortion at that point. I have provisionally concluded that the IM is in the headphones, but I have not yet done the measurements to confirm that.

Just worth noting the $30ish Asus DG (meant to be able to support 96khz natively but would like to see it tested) is a stripped down version of the Xense (which supports 192khz), the DG uses lesser headphone amp (TI seem to only provide IM standards for the Xense and not amp component used in DG), lesser audio chip, and lesser DAC.

My other PC (Asus M5A97 series system board) uses the on-board Realtek chip and its electrical output also seems to measure to be audibly clean.

Not going to comment about the rest as I have put forward a lot already, which I still stand by; those tests are stress testing and causing non-linear behaviour in the electronics/not a reflection of real world listening as the IMD needs to be cranked up to be audible so like a recording being on average at -70dbfs or quieter for peaks, and this is not what listening tests should be; same way JA uses the 19+20khz at specific watts to see how an amp copes under seriously abnormal stress.

When doing tests that may be breaking new ground I would like to control as many influences as possible to the greatest extent possible. We're taking an agnostic approach to a situation where nothing should be audible based on current theories. Therefore we can't reasonably take the same theories that we want to disprove and use them to prove that a certain influence doesn't matter.

IMO Everything needs to be as clean as is reasonably possible. There is no great trouble or expense involved with finding equipment that is clean according with the test that was provided. You just got to do the test and take reasonable actions based on its pretty clear outcome. If it is broken, even under higher stress than it may receive in actual use, and it is easy enough to have non-broken equipment, why not do it?

Regarding Asus, yeah only their higher range products are actually worth it IMO in terms of build and specification; unfortunately this is a moderate price jump from entry-budget priced cards/motherboards to their performance products.

I have no complaints about the performance of their econo-priced PCI/PCIE audio interface. I have no complaints about even their near zero priced audio interface in my Asus motherboard.

 

[Orb]

Sorry to interrupt, but most of this technical discussion is over my head, but I'm very interested to know if anyone, here or elsewhere, has duplicated Amir's results. I can't hear this stuff; never can. It would be good to know that's normal, not a personal defect.

Tim

Tim,
to pass you need to have a very specific approach (tbh I feel that way with any subtle ABX) in that you listen for a cue/s somewhere in the segment, once isolated what you feel is the difference (trait depends upon what the test and source content is) then you focus in on that part/s for the ABX; ideally you want to shorten the critical focus aspect to around 1-3 seconds with the localised segment it is in maybe of 6 seconds for switching-comparison.
Done a few ABX in the past (not hifi but involving audio transmission) and only way I found to get consistent results was to ensure methodical approach to the listening along the brief lines I mention above, Amir also posted more detailed steps on AVSF on how to do this current test - maybe he still knows which post it was and can link it.

Cheers
Orb

 

[Stereoeditor]

I promised Orb I would post some plots of intermodulation (or lack thereof) of some D/A headphone amplifiers using Arny Krueger's choice of ultrasonic tones. I will do so, most likely tomorrow.

View attachment MPrime HFIM39k41k0.pdf View attachment MPrime HFIM39k41k Wide.pdf

Here are two spectral plots of the Meridian Prime D/A headphone amplifier decoding 96kHz-sampled data representing tones at 39kHz and 41kHz, each at -6dBFS, the combined waveform peaking at 0dBFS. One plot is restricted to the audioband; there is almost no 2kHz product visible, the left channel (blue trace) being highest at -90dB. The other plot extends the measurement bandwidth to 100kHz; there are some higher-order products visible above the audioband, but nothing high in level even though the amplifier's output is just below visible clipping on an oscilloscope screen.

John Atkinson
Editor, Stereophile

 

[Orb]

I'm familiar with that particular presentation and have cited it myself many times. Pleas notice that it is dated 2003 which is about 3 years after I first posted my Jangling Keys file on my own web site. Just as soon as I saw it mentioned here I went back and reviewed it one more time. He duplicated my procedures which were on the web at the time pretty carefully, and duplicated my results. I don't disagree with his stuff and I don't see his stuff as disagreeing with mine. I'm not accusing him of stealing my idea because my idea was very consistent with accepted professional practice and knowledge at the time and for decades before it. I first saw keys jangling used as a source of test signals in the late 1970s, if memory serves.



I can predict it and even have simulated it, as well as measured it for real world equipment. It all depends on the equipment being used and the actual listening levels. However, since the stimulus is always ultrasonic, and much of the spurious responses are in a range where the ear is very sensitive, the responses are always more audible than the stimulus.

I mentioned that I think I have a case where it is very audible but not present in the electrical output of the sound card. I think the spurious response is > 2%.



The failure was with the subjective test. So far I have measured the output of the card at the headphone jack and find reasonably low distortion at that point. I have provisionally concluded that the IM is in the headphones, but I have not yet done the measurements to confirm that.



My other PC (Asus M5A97 series system board) uses the on-board Realtek chip and its electrical output also seems to measure to be audibly clean.



When doing tests that may be breaking new ground I would like to control as many influences as possible to the greatest extent possible. We're taking an agnostic approach to a situation where nothing should be audible based on current theories. Therefore we can't reasonably take the same theories that we want to disprove and use them to prove that a certain influence doesn't matter.

IMO Everything needs to be as clean as is reasonably possible. There is no great trouble or expense involved with finding equipment that is clean according with the test that was provided. You just got to do the test and take reasonable actions based on its pretty clear outcome. If it is broken, even under higher stress than it may receive in actual use, and it is easy enough to have non-broken equipment, why not do it?



I have no complaints about the performance of their econo-priced PCI/PCIE audio interface. I have no complaints about even their near zero priced audio interface in my Asus motherboard.

Yeah I commented much earlier on in this thread that presentation was 2003 and things do move on from then, case in point his difficulty back then finding true native 96/24 products and the good motherboards/components have advanced since then.
Well if you feel he was inspired by your work you should feel some pride considering his scientific and engineering background.
You mention his approach mirrors yours exactly; but Griesinger does with/without ultrasonic component and critically also reproduce only content above 20khz so IM is not masked, and used multiple sound levels to point consistent with amplifier distortion.
Also of importance IMO is the 2-tone IM test was repeatedly done with 6db increments in level (so the level dependence of any distortion could be measured).
Anyway he does go on to say:

Amplifier distortion can produce distortion products below 20kHz that are audible (with difficulty) in the absence of other signals below 20kHz.
But with a high quality amplifier these distortion products are not audible in the presence of even extraordinary ultrasonic sources such as rattling keys
Unless the amplifier is driven into clipping.

Just also to say he has taken the 2-tone IM even further with his test sweep slowly up in frequency, and the conclusion for this is still part of the above quote, caveats on equipment quality-well designed seeming to fit, but that is what should be used for listening tests anyway IMO.

Thanks
Orb