Audio DiffMaker

[Ducatista47]

This could end a lot of arguments. I don't like to argue but I do want to know what works and what doesn't. With this tool any system change can be evaluated. Room treatment, components, wire, a single capacitor or resistor, anything. Precise level matching is unnecessary and the result is heard, not plotted. As Kathleen Hanna said, "I wanna go!"

http://www.libinst.com/Audio%20DiffMaker.htm

[Wagner]

When to use Audio DiffMaker?
Testing for audible effects of

Changing interconnect cables (compensation for cable capacitance may be required)
Different types of basic components (resistors, capacitors, inductors)
Special power cords
Changing loudspeaker cables (cable inductance may need to be matched or compensated)
Treatments to audio CDs (pens, demagnetizers, lathes, dampers, coatings...)
Vibration control devices
EMI control devices
Paints and lacquers used on cables, etc.
Premium audio connectors
Devices said to modify electrons or their travel, such as certain treated "clocks"
Different kinds of operational amplifiers, transistors, or vacuum tubes
Different kinds of CD players
Changing between power amplifiers
General audio "tweaks" said to affect audio signals (rather than to affect the listener directly)
Anything else where the ability to change an audio signal is questioned




Paints and lacquers used on cables etc.?! Why, I've been wanting to scientifically end that argument FOREVER!

I TOTALLY missed it in my January, 2008 copy of *AudioXpress? :eek:

Thank you! :)

* Off topic, sorry, but does anyone here still subscribe to (or contribute articles to) AudioXpress since they went "digital" and dropped the paper option entirely? I did (dropped it), pretty shabby how they implemented it - I would like to hear how the "digital" "e-zine" is working out for them (or if it's even still up and running) and more importantly how you like it if you stuck with it. Was down to about 25 pages at the end anyway and the articles were, let's say, not what they used to be so I am very curious. PM commentary/converstation is fine if you feel so inclined
Thanks
T.W.

[LowPhreak]

If this thing really works I'd say, "halleluyah!" :hurray: Then I'd say, "well it's about time."

Thanks for the post, Ducati. :thmbsup:

[Mitchco]

One can find several DiffMaker tests on Archimago's blog. Here is one: http://archimago.blogspot.ca/2013/05/protocol-diffmaker-audio-composite-dmac.html

I have used DiffMaker as well:
http://www.computeraudiophile.com/content/513-jriver-mac-vs-jriver-windows-sound-quality-comparison/
http://www.computeraudiophile.com/blogs/mitchco/jriver-vs-jplay-test-results-156/
http://www.computeraudiophile.com/blogs/mitchco/flac-vs-wav-part-2-final-results-155/

DiffMaker has a few bugs, but the workarounds are in the above posts. DiffMaker is fun and educational - especially listening to the difference file.

[Ducatista47]

Mitchco, thank you for posting your efforts in this arena, and verifying for us that it works as explained. I lit up when I read about this tool. AES engineers, instead of salesmen or manufactures trying to send their daughters through college by selling ten units, very refreshing.

I suppose the horse crap will continue unabated, but now I can feel better about ignoring it. I have made most audio mistakes at one time or another, but at this late date in my life I think I am BS free and validation is so, so sweet.

[Mr. Widget]

What am I missing here? It appears this simply subtracts one signal from the other and you are left with the difference.

How does that help determine which is better?


Widget

[Ducatista47]

What am I missing here? It appears this simply subtracts one signal from the other and you are left with the difference.

How does that help determine which is better?


Widget
It is not to determine the subjective which is better, rather the objective does it do anything? And if so, what? Further, is it audible or is the change, for instance, 90dB down or out of the range of human hearing?

The latter point is of interest to me as well. I am friends with an audio guru who sometimes seems to get hung up on technology that boasts superiority of only theoretical benefit. Ladder DACs over Delta-Sigma DACs comes to mind, as does digital volume controls throwing away data (which begins at 56dB attenuation). I recall that you were bothered by the idea of brick wall filtering. It all happens past human hearing, so I do not share your concern. I recall Greg Timbers stuffing a sock or something in the Everest's Super Tweeter and hearing no difference at all.

[Mr. Widget]

It is not to determine the subjective which is better, rather the objective does it do anything? And if so, what? Further, is it audible or is the change, for instance, 90dB down or out of the range of human hearing?

The latter point is of interest to me as well. I am friends with an audio guru who sometimes seems to get hung up on technology that boasts superiority of only theoretical benefits. Ladder DACs over Delta-Sigma DACs comes to mind, as does digital volume controls throwing away data (which begins at 56dB attenuation.)But the objective, "Does it do anything?" can easily be yes, while subjectively we may not hear a difference. Alternatively, the comparison may be frequency, or THD, or something else... where the difference could be measurably insignificant, but we may not be comparing a factor that objectively and subjectively causes an audible difference.


Widget

[Ducatista47]

My point exactly. Differences you can't hear are of no consequence in listening to sound. Conversely, the idea that we can hear differences that cannot be measured has been proved to be complete fantasy.

[Mr. Widget]

I recall that you were bothered by the idea of brick wall filtering. It all happens past human hearing, so I do not share your concern. I recall Greg Timbers stuffing a sock or something in the Everest's Super Tweeter and hearing no difference at all.I do not recall the context of the filter conversation, but I guess I was speculating on possible audible differences of DACs...

On the "sock test", that was a quick observation in a hotel room listening to them for the first time. Having lived with the same speakers now for some time, I can attest to the fact that the super tweeters are audible. Whether or not they are necessary is a different conversation.


Widget

[Ducatista47]

We can agree that they are necessary for sales in the Japanese market!

[Mr. Widget]

My point exactly. Differences you can't hear are of no consequence in listening to sound.I would think no reasonable person would disagree... hence when a wire manufacturer shows how their winding improves the performance in the MHz range, it makes me scratch my head.


Conversely, the idea that we can hear differences that cannot be measured has been proved to be complete fantasy.You think? How can you come to that conclusion? I would suggest that if two items under test are measurably identical but in a controlled experiment humans can consistently perceive a difference then the measurements are incomplete.


Widget

[hsosdrum]

Anything can cause a subjective change in the way something sounds, since our brain can be influenced by much more than just the nerve impulses it receives from the auditory system. Since sound is created in the brain, anything that influences how the brain perceives sound is, indeed, changing that sound, even if that difference is not the result of a change in the nerve impulses generated by the auditory system.

Unless one is willing to admit that double-blind testing is the only way to accurately determine if something makes a sonic difference, there's absolutely no way to determine if any perceived sonic difference is the result of differences in auditory system nerve impulses or the result of something completely different, such as the listener having a vested emotional interest in there being a difference because they spent a shitload of money, or because they like the brand, or because the thing just looks so cool, etc.

Even if this DiffMaker device does reveal a difference between two electrical signals, there's no conclusive way to correlate that difference with any perceived sonic difference. The perceived sonic difference could be caused by something that has nothing to do with the difference being revealed by the DiffMaker device.

[Ducatista47]

You think? How can you come to that conclusion? I would suggest that if two items under test are measurably identical but in a controlled experiment humans can consistently perceive a difference then the measurements are incomplete.
Widget
I would suggest that consistency proves nothing other than the how much listeners want there to be a difference, at least in the absence of a measurable result. I'm with Ethan Winer and the AES on this one. I still respect your opinion about it.

[Mr. Widget]

I would suggest that consistency proves nothing other than the how much listeners want there to be a difference, at least in the absence of a measurable result. I'm with Ethan Winer and the AES on this one. I still respect your opinion about it.I guess I should have added blind or double blind. I absolutely agree that preconceived ideas are extremely powerful influences on the subjective "truth".


Widget

[Ducatista47]

Even if this DiffMaker device does reveal a difference between two electrical signals, there's no conclusive way to correlate that difference with any perceived sonic difference. The perceived sonic difference could be caused by something that has nothing to do with the difference being revealed by the DiffMaker device.
To clarify, Audio DiffMaker works in the audio realm, not the electrical or the electronic one. The end result, while it is easily displayed as well, is also produced in the audio realm. It finds differences between renditions detected by a microphone, a device (in the case of a decent one) several times more sensitive and discriminating that human hearing. But still an accepted analog for it. Listening to the difference, or the absence of one, is the test of whether you can hear it or not.

I think it is well thought out and simple but clever. The possible phobic reaction of people invested in making money or seeking validity in their purchases and preferences is not a refutation of the software. Science, as they say, is not a religion. It is true whether you believe in it or not!

[hsosdrum]

Within the range of human hearing, even the best microphone on Earth is definitely not more sensitive and discriminating than human hearing itself, not by a long shot. Regardless, the DiffMaker device can only quantify information that is represented by an alternating current—that's why it requires a microphone to convert the acoustic pressure variations from a speaker into an AC voltage. And every transduction step (the mic is a transducer) substantially changes the signal it receives. That's why no two microphones, even the very best ones, sound the same. Microphones may be accepted analogs for human hearing, but only because humans haven't yet invented anything that can do a better job. Just because a technology is the best available doesn't mean that it's as good as it needs to be to get the job done right.

Again, all the DiffMaker system can do is extract differences between different alternating currents (after it creates them by converting acoustic events via a microphone); it can't make any correlation between the differences it detects and the differences a listener may (or may not) detect.

[Wagner]

the idea that we can hear differences that cannot be measured has been proved to be complete fantasy.
That is an absolutely ridiculous statement
I believe it is not true
100% spurious in my opinion

If you insist that it is the truth, then please direct me to the paper or protocol that proved it
(not a reading list of articles or forum posts written by a bunch of folks who agree with you)

The laboratory results (and it's credentials) is all I am interested in

Thanks
Thomas

[Mr. Widget]

That is an absolutely ridiculous statement
I believe it is not true
100% spurious in my opinion

If you insist that it is the truth, then please direct me to the paper or protocol that proved it
(not a reading list of articles or forum posts written by a bunch of folks who agree with you)

The laboratory results (and it's credentials) is all I am interested in

Thanks
ThomasThomas, you have such a lovely way of expressing your opinions. Whether one agrees or disagrees... it just brightens one's day to read so many of your posts. :banghead:

Does your audio hobby make you happier in life or more miserable? Reading your posts makes me think you are very unhappy. If that is the case, I guess there isn't much you can do about it, however if you are not miserable, perhaps you could better express yourself.


Widget

[Mr. Widget]

Within the range of human hearing, even the best microphone on Earth is definitely not more sensitive and discriminating than human hearing itself, not by a long shot.I get your overarching point and in general tend to agree, however are you certain about the best mic/best ear comparison? The unit of one decibel is by definition the smallest sound increment that a human with normal hearing will perceive. A quality microphone will register small fractions of a decibel.


Widget

[DS-21]

I would suggest that if two items under test are measurably identical but in a controlled experiment humans can consistently perceive a difference then the measurements are incomplete.

In theory that is exactly right.

In practice...has that ever actually happened (at least within the last quarter-century or so)? I'm curious if you have an example you can point to, because I cannot think of one, short of willfully incomplete measurement sets (i.e. speakers equalized to the same nearfield axial response but with different dispersion patterns).

[Mr. Widget]

In theory that is exactly right.

In practice...has that ever actually happened (at least within the last quarter-century or so)? I'm curious if you have an example you can point to, because I cannot think of one, short of willfully incomplete measurement sets (i.e. speakers equalized to the same nearfield axial response but with different dispersion patterns).How about amplifiers? There are many that seem to measure essentially identically but in my experience do not sound the same. Now I know people who I hold in high esteem who claim there is no sonic difference in quality amplifiers. I have to respectfully disagree with that statement.

I have experienced numerous cases where people both interested and disinterested in high fidelity have recognized differences in amps when no one present knew which test subject was being auditioned.


Widget

[Ducatista47]

How about amplifiers? There are many that seem to measure essentially identically but in my experience do not sound the same. Now I know people who I hold in high esteem who claim there is no sonic difference in quality amplifiers. I have to respectfully disagree with that statement.

I have experienced numerous cases where people both interested and disinterested in high fidelity have recognized differences in amps when no one present knew which test subject was being auditioned.
Widget
That scenario sound like a good use of Audio Diffmaker.

[Mr. Widget]

That scenario sound like a good use of Audio Diffmaker.As I understand it the Diffmaker will show the difference in frequency response which should be insignificant. So I don't think it will corolate with the perceptual difference.


Widget

[Ducatista47]

As I understand it the Diffmaker will show the difference in frequency response which should be insignificant. So I don't think it will corolate with the perceptual difference.

Widget

It will, with a proper microphone, demonstrate any sonic difference you could actually hear. That is probably why it was designed to have the user listen to the results. I believe something that is different but 90dB down cannnot possibly affect what we hear. There are people saying that jitter 112dB down leads to audible artifacts; I am not one of them. It does appear that selling clocking devices for thousands of dollars appeals to some; certainly not me, even if I were wealthy.

I have harbored a suspicion for some years that I have spent too much on amplification, and a DAC. At least I realize it. Most listeners with as much invested in their electronics would probably not want to know. You and I both know that the big differences are in speakers and headphones, and source material. Face it, most audiophiles will have little interest in myth busters like this software. Finding out you have been "worshiping a false god" is a relief for some but most find it upsetting. It becomes pretty obvious after doing this hobby for a long time that individual listeners like their preferred distortion. While there is nothing wrong with that, they do not, generally, want to admit it. They prefer to believe words like "better" are not subjective.

The least contentious aspect of this tool is most likely the ability to demonstrate when something does nothing at all.

Edit: This AES workshop report by Ethan Winer proposes that our tool box for measuring audio is more comprehensive than we usually realize. 3:25 to 5:40 lays out his reasons for respecting the power of null analysis, but I find the entire video a reasoned presentation. I accept his conclusion that "If there really was something about audio fidelity that science was not aware of, it would have been revealed years ago by nulling". He also clearly knows and explains the issues involving listening and preference that do not rely on fidelity. https://www.youtube.com/watch?v=Zvireu2SGZM&nohtml5=False

[1audiohack]

While I haven't yet looked beyond the front page link provided I believe this could be a very powerful tool. There is a difference mode in TEF that lets you compare measurements if the parameter set is identical. This is great for testing drivers or comparing acoustical treatment and much more but it is a visual graph comparison only.

I also believe that listening to things with a microphone is instructive. Most measurement systems used at a hobby level employ a $50. omnidirectional mic. They nearly don't even care which way they are pointed.

Try listening to your system through a quality cardioid measurement mic and headphones in real time while moving and pointing the mic around the room. This will give you some idea of just how much filtering the gray matter computer between your ears is doing, and help you focus on what and where improvements can be made. This is much like soloing a channel on a mixing desk.

I believe that any tool that can bring audio one more step out of the abyss of subjectivity and into objectivity is a good tool.

I agree with Widget that we do not yet have all the tools.

Barry.

[Mr. Widget]

I have harbored a suspicion for some years that I have spent too much on amplification, and a DAC. At least I realize it.
I have had $20K amplifiers in my home system that I didn't think sounded as good as $4,000 amps. So, yes, I would agree it is easily done. But then there are other reasons to choose one piece of gear over another. I had a shoot out between the Parasound Halo JC-2 preamp and the ML No 326S. I couldn't hear a definitive difference between these two excellent performing preamps... I bought the more expensive one because I preferred the responsiveness of the remote volume control and it's general UI.



Edit: This AES workshop report by Ethan Winer proposes that our tool box for measuring audio is more comprehensive than we usually realize. 3:25 to 5:40 lays out his reasons for respecting the power of null analysis, but I find the entire video a reasoned presentation. I accept his conclusion that "If there really was something about audio fidelity that science was not aware of, it would have been revealed years ago by nulling". He also clearly knows and explains the issues involving listening and preference that do not rely on fidelity. https://www.youtube.com/watch?v=Zvireu2SGZM&nohtml5=FalseI'd love to have a chat with him, but based on what I've gleaned from a quick overview I'm not convinced. I am far from the "Rhythm and Pace" school of thought... I have no idea what reviewers are talking about when they dive deep into the subjective gobbledygook, but I have experienced sonic differences that surprised me based on my understanding of the science.


Widget

[Mr. Widget]

Try listening to your system through a quality cardioid measurement mic and headphones in real time while moving and pointing the mic around the room. This will give you some idea of just how much filtering the gray matter computer between your ears is doing, and help you focus on what and where improvements can be made. This is much like soloing a channel on a mixing desk.
Or even look at the plots of two measurements taken a few cm apart. Run them through the Diffmaker and you'll see/hear a huge difference and it is the same system in the same room.???

I firmly believe we do not hear the way we measure. Measurements are great, don't get me wrong... when I subjectively knew there was something "wrong" in my room, it took objective measurements and averaging technology to localize what I was hearing and allow me to correct it. I tried futilely to take the problem on with only my ears.


Widget

[DS-21]

How about amplifiers? There are many that seem to measure essentially identically but in my experience do not sound the same. Now I know people who I hold in high esteem who claim there is no sonic difference in quality amplifiers. I have to respectfully disagree with that statement.

I have experienced numerous cases where people both interested and disinterested in high fidelity have recognized differences in amps when no one present knew which test subject was being auditioned.


I've yet to hear competent* amplifiers sound different from one another with voltage output carefully matched**, but if there is something to hear, that's what Mr. Waslo's software will uncover by playing back only the difference signal. It's neat software. Very useful for exposing spectral colorations caused by high source impedance amps, or upper midrange power compression on speakers with those little garbage AMT tweeters.

*"competent" = low noise floor, flat FR, source impedance sufficiently low enough that it doesn't materially affect the frequency response of the driven speaker, sufficient power to drive the intended speakers to the desired SPL peaks.

**most "differences" arise from minute level variances, and demos rarely feature match levels with a voltmeter...

[Mr. Widget]

Very useful for exposing spectral colorations...I understand that, and most quality amps or other line stage devices have little if any spectral differences or colorations. The differences I am listening for are not deviations in frequency or tonal colorations, I am listening for the much more elusive spatial cues in stereophonic recordings.

There are also qualities that are much harder to describe, but often lower quality (not lower cost) electronics sound congested and tend to sound more compressed with less dynamic detail... or detail in general. (Not to be confused with a slightly elevated midrange which can subjectively sound like an increase in detail... we see this often in speakers.)

To continue the speaker analog... compare a beryllium diaphragmed driver with a more conventional one. The frequency response could be identical, but the acceleration factor and distortion levels are not and the subjective difference is very real.


Widget

[Ducatista47]

I also believe that listening to things with a microphone is instructive. Most measurement systems used at a hobby level employ a $50. omnidirectional mic. They nearly don't even care which way they are pointed.

Try listening to your system through a quality cardioid measurement mic and headphones in real time while moving and pointing the mic around the room. This will give you some idea of just how much filtering the gray matter computer between your ears is doing, and help you focus on what and where improvements can be made. This is much like soloing a channel on a mixing desk.

Barry.


Or even look at the plots of two measurements taken a few cm apart. Run them through the Diffmaker and you'll see/hear a huge difference and it is the same system in the same room.???

Widget
Total agreement. Small differences in listening location, like getting up to change something and sitting down again, have long been known to alter what is heard. A late friend who ran an audio dealership for years would say things like, "I have never heard an interconnect or speaker wire that didn't change the sound. It is not always a good change, but there always has been one."

I knew better than to propose that a movement of a centimeter would change a lot. He didn't want to hear that reasoning. He made a lot of money selling wire.

That's another reason DiffMaker seems like a useful tool to me. The microphone setup, unlike our ears, doesn't move between recordings.

[Ian Mackenzie]

I have no doubt differential can determine a change.

However as Floyd Toole has proven we largely listen with our eyes when it comes to sound reproduction!

This is why blind testing is important.

In Tooles paper on you tube he explains in laymans terms whi this is the case.

Going further, the research outlines what in fact the ear/brain is sensitive to in terms if changes in sound reproduction.

Some changes we are quite tolerant of while others are not .

This is particularly relevant to evaluation loudspeakers frequency response and impact of the listening room.

Correlate this study with enough data and you have grounds for determining what sounds good and what doe not!

Unfortunately the audio consumer is always on the look out for what could improve his listening experience and this is the motivation of the audio mafia to make money.

Twisting the circumstances with massive cables that are visually appealing to the eyes screws with the brains logic and you easily get a "yes" it sounded better.

However, what the listener (the customer) does not know the listener does not know in terms of the risks of good and audio reproduction beyond what is printed in the advertising spec sheet like 0.002 % distortion.

On the other hand there is no argument a JBL 1500 AL driver is superior to a JBL 2235 driver.

But in a double blind test what aspects of the audio reproduction from a range of completed loudspeakers using these drivers will the listen hear as audible likes and dislikes?

A system with good drivers but in a poorly executed design may end up not being preferred to lesser quality drivers in a well executed system and so it goes on.

This is why loudspeakers advertised with expensive tweeter may not be rated as appealing to a lower cost tweeter that is mounted with a correctly designed wave guide and crossover network.

But if the listener first visually sees and identifies the expensive tweeter he may indicate he preferred the system using that tweeter while a under a blind test he may prefer the other tweeeter with the wave guide.

With amplifiers for a long time the spec sheet ruled. These days research indicates that some 3rd harmonic distortion with increased amplitude(volume) is preferred but not higher odd order harmonics.

My own interpretation is that the listening experience is like a photographer looking through a lense of an SLR camera and taking a picture. The printed image is what you see in the end.

How do you judge what is better image between two or more photos taken by different photographers with a different lenses of the same subject?

Throw marketing claims in the mix about a particular lense and the visual appearance of a big chunk of glass and you might automatically prefer the image taken with that lense over another.

[Mitchco]

One can find several DiffMaker tests on Archimago's blog. Here is one: http://archimago.blogspot.ca/2013/05/protocol-diffmaker-audio-composite-dmac.html

I have used DiffMaker as well:
http://www.computeraudiophile.com/content/513-jriver-mac-vs-jriver-windows-sound-quality-comparison/
http://www.computeraudiophile.com/blogs/mitchco/jriver-vs-jplay-test-results-156/
http://www.computeraudiophile.com/blogs/mitchco/flac-vs-wav-part-2-final-results-155/

DiffMaker has a few bugs, but the workarounds are in the above posts. DiffMaker is fun and educational - especially listening to the difference file.

I should have mentioned the above links also include ABX listening tests, plus the difference files one can download and listen to.

Which is the crux of the matter, how does one correlate the visuals to the audibles?

This article http://www.computeraudiophile.com/content/520-fun-digital-audio-%96-bit-perfect-audibility-testing/ contains amplitude audibility testing and bit-depth audibility testing. From the article, "Note, if you are following along with the downloaded files, adjust the volume for your typical listening level and remember the setting. The idea here is to not only compare the files, but through the course of the listening tests, the difference levels will change, reducing to inaudible. It is educational to listen to the difference files over the course of the test using the same monitor level throughout.

This approach helps put into perspective how we perceive relative loudness. The only way to achieve this is to set the volume control once and leave it there. However, occasionally we will need to increase the volume to maximum to find the noise floor. Be sure to mark the original level so that it can be returned to."

From the article, in conclusion: "I set out to determine how far away from bit-perfect I can hear an audible difference in sound quality. In the case of adjusting amplitude with a digital eq, my audibility threshold is about 1 dB of change. 4dB of eq was easy to hear, but I could not detect a .1 dB eq change. In the case of adjusting bit-depth, my audibility threshold is around 10 to 12 bits, using rock music as the sample. At 8 bits I could easily detect a change, but not at 12 bits. In both the amplitude and bit-depth test cases, it appears that my audibility threshold level is around -70 dBFS when comparing an altered file to the original file."

I wrote those articles to satisfy my own curiosity as to what was or wasn't audible to my ears. If one looks for scientific research on psychoacoustics, my results seem to be consistent with other's, when comparing the original file with an altered file, listening at a reference level of 83 dB SPL C weighting, slow response, on a SLM. It would be interesting to see other forum members results if giving the files a listen.

A good online site for audibility testing: http://www.audiocheck.net/ in case one has not seen it.

With respect to DiffMaker, from Bill's AES paper: http://www.libinst.com/AES%20Audio%20Differencing%20Paper.pdf "The difference test doesn’t detect just aurally relevant changes, it detects audio band changes of any kind."
I found the paper a good read to understand the algorithms used in the software.

Based on my own audibility testing, I concluded if I measure a difference file to be below -70 dbFS in DiffMaker or Audacity or whatever, then I am going with that it is not audible to my ears and carry on.

Enjoy the music!

[DS-21]

I understand that, and most quality amps or other line stage devices have little if any spectral differences or colorations. The differences I am listening for are not deviations in frequency or tonal colorations, I am listening for the much more elusive spatial cues in stereophonic recordings.

I really hope you don't actually expect "spatial cues" from a mere gain block. Unless you're talking about one with some sort of signal processing, such as a crossfeed circuit on a headphone amp. Or one with really poor channel separation.


To continue the speaker analog...

That is a mistake, because there is no reasonable analog between a mere gain block and a transducer, but going on...


compare a beryllium diaphragmed driver with a more conventional one. The frequency response could be identical, but the acceleration factor and distortion levels are not and the subjective difference is very real.

I don't subscribe to "magic materials" thoughts either. The bottom line is, drivers sound different because of either motor issues or diaphragm resonances. Nothing magical, and nothing not thoroughly explained by our current models. Even if one is made out of a crystallized fairy dust matrix and the other out of dog poop.

Be can push resonances higher than other current materials, if used well. A difference that's easily measurable. (That's why the TAD Reference line has bigger midranges than the TAD Evolution line; the Mg cone midrange in the Evos needs to be smaller to play as high cleanly, because of diaphragm resonances.) But otherwise there's nothing special about it, except that audio marketers have glommed onto the word as some sort of fetish talisman. Note that JBL themselves have moved away from it and towards cheap plastic rings in a novel configuration for their new flagship CD line. I've not read many complaints about the M2's top end, though unfortunately I still haven't had the opportunity to hear them for myself.


I have no doubt differential can determine a change.


However as Floyd Toole has proven we largely listen with our eyes when it comes to sound reproduction!

Yup. The difference is that it's much much easier to take two recordings with DiffMaker than to run a serious controlled listening test. Ultimately less resolving (just because DiffMaker gives you something other than silence, doesn't mean the difference is audible or significant) but a whole lot easier.

[Ian Mackenzie]

I understand that, and most quality amps or other line stage devices have little if any spectral differences or colorations. The differences I am listening for are not deviations in frequency or tonal colorations, I am listening for the much more elusive spatial cues in stereophonic recordings.

There are also qualities that are much harder to describe, but often lower quality (not lower cost) electronics sound congested and tend to sound more compressed with less dynamic detail... or detail in general. (Not to be confused with a slightly elevated midrange which can subjectively sound like an increase in detail... we see this often in speakers.)

Widget

I think Mr Widget is referring to transparency and resolution.

Just like listening to a nice Chesky recording and then a non Chesky producition. Assuming your playback system has the transparency and resplution those spatial quality will be audible they are otherwise lost or masked in a lesse system.

For example comparing the PSS 600 power amp l once raved about that had amazing specs on paper to the Pass Labs 250.5 the amount of low level spatial information is astonishing.

But l use a high resolution source and loudspeakers when making that statement.

This then becomes an audio education when one goes back to lower resolution recordings and equipment.

If l used ITunes as a source l would not be making test statement.

[Mr. Widget]

I really hope you don't actually expect "spatial cues" from a mere gain block...I'm not expecting it to create them, but if you've actually listened to a variety of circuits you must have noticed that the perceived soundstage will vary... perceived musical instrument location within the sound field etc. Of course this presupposes that the listener is sitting in the center of a stereophonic playback system and are actually listening as opposed to casual listening off to the side of the system etc.


I don't subscribe to "magic materials" thoughts either.myself....I was thinking of the basic physics of the materials... which as you pointed out affects relatively easily measured differences in resonance and distortion. The "analogy" I was trying to make was that by substituting materials it would be possible to have nearly identical frequency responses and yet different sound qualities.


Widget

[gasfan]

I'm not expecting it to create them, but if you've actually listened to a variety of circuits you must have noticed that the perceived soundstage will vary... perceived musical instrument location within the sound field etc. Of course this presupposes that the listener is sitting in the center of a stereophonic playback system and are actually listening as opposed to casual listening off to the side of the system etc.

I was thinking of the basic physics of the materials... which as you pointed out affects relatively easily measured differences in resonance and distortion. The "analogy" I was trying to make was that by substituting materials it would be possible to have nearly identical frequency responses and yet different sound qualities.


WidgetI can see this software being especially useful in identifying malfunctioning components. Perceived sound stage only varies among those circuits whose R and L signal levels are not identical. Differences are infinite. Accurate is always the same.

[Ian Mackenzie]

Channel separation is another factor as in signal to noise ratio.

There is a diminishing return on low distortion if the system noise floor mask distortion products.

Typically it's the volume control and the inherent noise floor of the circuit that effect inter channels balance and perceived sound stage.

Muse of Japan now have a good digitally control analogue volume control chip.

The chip has an internal resister ladder that is switched seamlessly.

This chip is finding its was into hi end preamps because it offers lower noise = spatual cues from low level detiail in recordings while holding exact channel balance.

[Ian Mackenzie]

I don't accept the comment of 1 db of change when evaluating the L Pad levels of 4 way loudspeaker.

Overall system level 1 db maybe an indication of the threshold of a change in amptitude.

However that is what the ear brain is acutely sensitive to.

If when adjusting L pad levels 0.5 db is discernible between bass/mid/high frequency bands.

This supports evidence that -+ 0.25 db for riaa phone equalisation is regarded as accurate riaa equalisation.

I think this would be a far more useful test for the software.

[gasfan]

Channel separation is another factor as in signal to noise ratio.

There is a diminishing return on low distortion if the system noise floor mask distortion products.

Typically it's the volume control and the inherent noise floor of the circuit that effect inter channels balance and perceived sound stage.

Muse of Japan now have a good digitally control analogue volume control chip.

The chip has an internal resister ladder that is switched seamlessly.

This chip is finding its was into hi end preamps because it offers lower noise = spatual cues from low level detiail in recordings while holding exact channel balance.

That's all well and good but the issue I was alluding to in Widget's post refers to channel balance at the output stage of a ss amp. If quiescent current is not held to within 1/10th of a mv between channels, nothing you can do afterward will restore what's been lost. Maintaining the phase relationship between channels is the most critical factor in reproducing the stereo image. Sonically it's similar to speakers out of phase to an extent. Especially bottom end which is often recorded in mono. You may not notice it because you are listening to two speakers with information coming from two sources. But as the mismatch increases, you hear less and less stereophonic spatial cues until all you have is
basically two sources. It's kind of like stereo. But you're being fooled. If 95% of us would simply go out of our way to truly match quiescent current in our amps, we'd stop

trying to tweak the life back into the music because that's where it gets lost.

[Ian Mackenzie]

well that's all well and good too but l doubt the crossover networks (after the amp) are any where near that tolerance and given this impacts on the phase response of the left and right channel the mismatch in production of the amp left and right channel is in significant, like 100/1.

Pass labs amps have super symmetry but that is to cancel distortions by a factor of 20 db within the balanced output stage of arch channel.

Some people say let an amp warm up for two hours to ensure everything is stable and work in the right temperature.

Perhaps that is why leaving a preamp on indefinitely is common practise.

But l don't think this relates to bias imbalance.

Take this that most crossover caps are 5%, L inductors 5% in production l find it unlikely the networks would be hand matched with a precision LCR meter.

Then look at the gross room in balance due to interaction above the Schroder frequency due to lack of room symmetry in s typical domestic room (critical according to Floyd). Compared to any phase mismatch up stream else where this is like 1000/1.

The work by Floyd and Geddes pin points the critical aspects of phase and amplitude in audio reproduction.

It's quite intuitive to read their papers.

What l am saying is in electronics it's all relative.

My own experience is that increased bias current in preamps and power amps increases apparent image depth.a typical audio chip is biased to 0.1 Ma. Compared to a discrete opamp l have built biased to 10 Ma the image depth and micro dynamics are superior.

Most commercial power amp run tiny amounts of output stage bias current and typically rely on feedback in various topologies to arrive a marketable specifications.

Most of them sound terrible compared to an ML, Passlabs or similar that make few concessions in heat sink real estate due to bias current.

The better desks run discrete opamps for this kind of audio performance where the signal would otherwise be scrubbed by numerous chip opamps stages in the recording process.

The Audio Diff maker might be useful in recording QA when Compared to the acoustics domain specific aspects of The human ear/brain make some issues in significant and other critical. That stuff is where the IP is useful .

Put it another way in a optimum acoustic environment the electronics are not on the spectrum, it's the loudspeaker.

[gasfan]

Theory is one thing and as important as it is, practical observation is what counts. I would love to have a shoot out over this exact issue. I can guarantee heads will spin. In any case I challenge anyone to prove me wrong. Just be sure the settings haven't drifted by the time you put the cover back on. This is exactly why a wide margin of tolerance is considered acceptable. Everybody knows it's going to drift. But has anyone ever made sure it didn't just to see? Hence two identical amps will almost always sound different. No one questions it because on paper it shouldn't matter. On a graph, approaching equilibrium, sonic improvement would look like an exponentially ascending line that quickly straightens out on either side within 1/10th of a mv of difference. Test it for yourself.

Btw, I sold a Meridian 559 a while back because it's 'auto-bias' function was no where near precise enough.

[hsosdrum]

I get your overarching point and in general tend to agree, however are you certain about the best mic/best ear comparison? The unit of one decibel is by definition the smallest sound increment that a human with normal hearing will perceive. A quality microphone will register small fractions of a decibel.


Widget

True, but measurement mics don't pick-up sound the same as human ears—only a binaural head does that. Once you're talking about a mic sitting on a stand it's an apples and oranges comparison with human hearing, which taints any result. (This is one of many reasons why we can hear differences we can't yet measure.)

And this doesn't even get into the brain's ability to process the nerve impulses it receives, which is far greater than any audio measurement system extant.

[hsosdrum]

How about amplifiers? There are many that seem to measure essentially identically but in my experience do not sound the same. Now I know people who I hold in high esteem who claim there is no sonic difference in quality amplifiers. I have to respectfully disagree with that statement.

I have experienced numerous cases where people both interested and disinterested in high fidelity have recognized differences in amps when no one present knew which test subject was being auditioned.


Widget

Amps that measure identically can (and do) sound different because once you connect them to a speaker they become part of a larger circuit, and the speaker part of that circuit absolutely influences how the amplifier part performs (and visa-versa). It's impossible to perform measurements on an amp when it's connected to a speaker because you can't be sure if you're measuring the amp or the speaker's influence on it. That's why they measure amps with them connected to test resistors: the resistors eliminate variables. But when you measure an amp connected to resistors you're measuring an incomplete circuit that doesn't behave like the one that's formed when you connect the amp to a speaker. So the measurements, like the circuit, are also incomplete: they cannot tell us enough about how the amplifier performs in the real world.

[Ian Mackenzie]

Originally Posted by Mr. Widget

I'm not expecting it to create them, but if you've actually listened to a variety of circuits you must have noticed that the perceived soundstage will vary... perceived musical instrument location within the sound field etc. Of course this presupposes that the listener is sitting in the center of a stereophonic playback system and are actually listening as opposed to casual listening off to the side of the system etc.

I was thinking of the basic physics of the materials... which as you pointed out affects relatively easily measured differences in resonance and distortion. The "analogy" I was trying to make was that by substituting materials it would be possible to have nearly identical frequency responses and yet different sound qualities.


Widget


I can see this software being especially useful in identifying malfunctioning components. Perceived sound stage only varies among those circuits whose R and L signal levels are not identical. Differences are infinite. Accurate is always the same.

I am not sure I agree that your hypothesis is correct and would related the the pshyco acoustic perceptions as you indicate.

I agree that if there is a channel imbalance in amplitude this will certainly effect sound stage shifts and the volume control is documented conclusively to mess up the sound stage over its range of adjustment. Scientists like Doug Self have spent a lifetime looking a solutions.

My take on this is The Widget was referring to different circuits in different amplifiers, ie the gain stage and associates stage like the volume control and or balance control.(not differences in amplifers over time or the same model and one location not performing as well as another due to mal adjustment.)

What I think The Widget was saying is that one preamp or power amp can by design have an impact on the sound stage.

If the volume is static and the levels are perfectly matched the sound stage can perceptually seem different.

Other factors suporting this including independant power supplies and earthing and PCB paylout fundermentally impact on the apparent percieved sound stage. This is acknowledge by professionals like John Curl.

The selection and type of semiconductors can also have a significant impact on sound quality as does how the devices and the surrounding circuits are set up.

Lets talk practically for a moment:

A while ago I re build a faulty SAE 50 watt / channel amp with modern semi conductors and new PS supply caps.

Some of the parts had previously been replaced with the incorrect substitute transisters!

According to the owner, the subjective improvement was night and day!

Does this correlate to perceived changes in sound stage?

It was while ago and all I can say was it performed far better than it had any right to.

The improvement in clarity and definition was remarkable but I let the owner draw his own conclusions.

In a rare show I faith I support The Widgets comments.

In theory the CMRR (the ability of a stage to reject noise or chatter on the supply rails) in a circuit designs can be good or bad depending on the design desicisons and budget of the production. In theory this might mess up pereived soundstage.

In practise bais current can drift with temperature but it normally difts in a linear manner with both channels as the VAS is effected by temperature.

The hotter the amp gets the higher the bias.

In a class A/B amps they use elaborate bias contols to ensure quiestent current is stable, sensors on heat sinks and some transisters now have inbuilt thermeral sensors to ensure rapid bias control. All this does is turn on the power transisters by a certain amount to control crossover distortion at low power levels 1-3 watts and to stop the amplifer destoying itself as the quiestent current would otherwise continue to rise and till the power transisters blew.

In your comment on the bias per mv, this will depend on the value of the emmiter resister and their and the matching of the output devices.

Most class A/B amps run around 50 ma of queisent current in the output stage.

Assuming 0.2 ohm emmiter resisters and say 2 parrellel devices, then 0.005 (5 millivolts) across each of the resisters that would be 50 ma bias on the output outstage.

What you are saying is 1/10th accurancy in bias current is required for stable stereo image.

That would be like 0.0045 mv or 0.0055mv across the emmiter resisters. This would decrease the output stage bias down to 45 ma or increase to 55 ma.

Thats 10% change in bias current but its more about the effect on the amps crossover distortion at low power levels, like 1-3 watts.

At higher power levels the amp goes into class B.

While I get it that matching quiesent current between L + R is desirable I would suggest this is not likely to impact on sound stage.

The other factors I mentioned above are going to swamp this.

That said the matching or non match of devices is going to be a far the most significant issue effecting quiestent current in a production amp than incorrect adjustment. Throw in 40-60 db of feedback, that is there to flatten out any wrinkles.

However, I will fire the question to Doug Self and see what he comes back with?

In Class A amps this is important and they are usually matched within 5%.

I know Pass Labs adjust for the on-lid bias condition after a long burn in.

[gasfan]

Originally Posted by Mr. Widget

I'm not expecting it to create them, but if you've actually listened to a variety of circuits you must have noticed that the perceived soundstage will vary... perceived musical instrument location within the sound field etc. Of course this presupposes that the listener is sitting in the center of a stereophonic playback system and are actually listening as opposed to casual listening off to the side of the system etc.

I was thinking of the basic physics of the materials... which as you pointed out affects relatively easily measured differences in resonance and distortion. The "analogy" I was trying to make was that by substituting materials it would be possible to have nearly identical frequency responses and yet different sound qualities.


Widget



I am not sure I agree that your hypothesis is correct and would related the the pshyco acoustic perceptions as you indicate.

I agree that if there is a channel imbalance in amplitude this will certainly effect sound stage shifts and the volume control is documented conclusively to mess up the sound stage over its range of adjustment. Scientists like Doug Self have spent a lifetime looking a solutions.

My take on this is The Widget was referring to different circuits in different amplifiers, ie the gain stage and associates stage like the volume control and or balance control.(not differences in amplifers over time or the same model and one location not performing as well as another due to mal adjustment.)

What I think The Widget was saying is that one preamp or power amp can by design have an impact on the sound stage.

If the volume is static and the levels are perfectly matched the sound stage can perceptually seem different.

Other factors suporting this including independant power supplies and earthing and PCB paylout fundermentally impact on the apparent percieved sound stage. This is acknowledge by professionals like John Curl.

The selection and type of semiconductors can also have a significant impact on sound quality as does how the devices and the surrounding circuits are set up.

Lets talk practically for a moment:

A while ago I re build a faulty SAE 50 watt / channel amp with modern semi conductors and new PS supply caps.

Some of the parts had previously been replaced with the incorrect substitute transisters!

According to the owner, the subjective improvement was night and day!

Does this correlate to perceived changes in sound stage?

It was while ago and all I can say was it performed far better than it had any right to.

The improvement in clarity and definition was remarkable but I let the owner draw his own conclusions.

In a rare show I faith I support The Widgets comments.

In theory the CMRR (the ability of a stage to reject noise or chatter on the supply rails) in a circuit designs can be good or bad depending on the design desicisons and budget of the production. In theory this might mess up pereived soundstage.

In practise bais current can drift with temperature but it normally difts in a linear manner with both channels as the VAS is effected by temperature.

The hotter the amp gets the higher the bias.

In a class A/B amps they use elaborate bias contols to ensure quiestent current is stable, sensors on heat sinks and some transisters now have inbuilt thermeral sensors to ensure rapid bias control. All this does is turn on the power transisters by a certain amount to control crossover distortion at low power levels 1-3 watts and to stop the amplifer destoying itself as the quiestent current would otherwise continue to rise and till the power transisters blew.

In your comment on the bias per mv, this will depend on the value of the emmiter resister and their and the matching of the output devices.

Most class A/B amps run around 50 ma of queisent current in the output stage.

Assuming 0.2 ohm emmiter resisters and say 2 parrellel devices, then 0.005 (5 millivolts) across each of the resisters that would be 50 ma bias on the output outstage.

What you are saying is 1/10th accurancy in bias current is required for stable stereo image.

That would be like 0.0045 mv or 0.0055mv across the emmiter resisters. This would decrease the output stage bias down to 45 ma or increase to 55 ma.

Thats 10% change in bias current but its more about the effect on the amps crossover distortion at low power levels, like 1-3 watts.

At higher power levels the amp goes into class B.

While I get it that matching quiesent current between L + R is desirable I would suggest this is not likely to impact on sound stage.

The other factors I mentioned above are going to swamp this.

That said the matching or non match of devices is going to be a far the most significant issue effecting quiestent current in a production amp than incorrect adjustment. Throw in 40-60 db of feedback, that is there to flatten out any wrinkles.

However, I will fire the question to Doug Self and see what he comes back with?

In Class A amps this is important and they are usually matched within 5%.

I know Pass Labs adjust for the on-lid bias condition after a long burn in.

Yes, bias drifts in a linear fashion...for the most part. Some say their amp sounds better after 10 min. of play, some say 30 etc., some say no difference. Nelson Pass seems to think it's an important issue. I've had this debate many times over the years. Conclusions such as yours are the consensus. I was following banter on DIY a while ago when the topic of bias current popped up. As soon as the statement "I adjust it while listening" came up, the conversation abruptly ended with no response. I've been doing just that for over 30 years. However I replace the pots with 25 turn if the amp doesn't already have them. There's a local tech here in my town that did finally venture to actually take me to task on this and is now convinced. In the first of our many discussions, he claimed quiescent current really doesn't have much to do with sq as long as crossover distortion has been eliminated. This guy is a well known restoration tech who receives gear from all over the world. The reason I responded to Widget's comment is because imo, he's describing exactly what everyone's experience is including mine. But the focus and attention surrounding the issue has and continues to be misdirected. I don't doubt your stature, credentials, or expertise. I get that a person such as yourself is not going to be talked into foolishness. I don't doubt everything you've said is correct, except for one.
And so I continue to harbor an unkept secret it seems. Sometimes knowledge gets in the way.

[Ian Mackenzie]

I get it and sometimes your own discovery is what matters.

If you get the chance have a listen to an amp with a relatively high bias current.

Then disconnect one channel and connect that channel to a amp with quiesant only current.

Then match all the levels and play the same tunes to determine if the sound stage changed.

This would prove your point.

[Mr. Widget]

What I think The Widget was saying is that one preamp or power amp can by design have an impact on the sound stage.

If the volume is static and the levels are perfectly matched the sound stage can perceptually seem different.Exactly.

For example, I have inserted an analog EQ into a system and even though it was set at unity gain and no EQ had been applied there was an apparent collapse in stage depth and an overall congestion of the sound. Removing this additional line stage, the original soundstage returned.

To veer back on topic, I am not sure that a simple difference circuit could pick this up. If it can demonstrate minor shifts in phase and other distortions that is pretty cool, but from the presented literature it appears to focus on frequency response.

Over the years I have experienced a wide array of "interesting" changes to the sound that equipment substitution has caused... some would definitely scream at you when compared via the DiffMaker, but I don't know if others would. My main point is that not revealing a difference in a simple test does not mean that an unbiased (unrelated to quiescence ;)) yet careful listener will not perceive a change.


Widget

[gasfan]

I get it and sometimes your own discovery is what matters.

If you get the chance have a listen to an amp with a relatively high bias current.

Then disconnect one channel and connect that channel to a amp with quiesant only current.

Then match all the levels and play the same tunes to determine if the sound stage changed.

This would prove your point.

Okay, thanks but I've already proven it to myself.

[gasfan]

Exactly.

For example, I have inserted an analog EQ into a system and even though it was set at unity gain and no EQ had been applied there was an apparent collapse in stage depth and an overall congestion of the sound. Removing this additional line stage, the original soundstage returned.

To veer back on topic, I am not sure that a simple difference circuit could pick this up. If it can demonstrate minor shifts in phase and other distortions that is pretty cool, but from the presented literature it appears to focus on frequency response.

Over the years I have experienced a wide array of "interesting" changes to the sound that equipment substitution has caused... some would definitely scream at you when compared via the DiffMaker, but I don't know if others would. My main point is that not revealing a difference in a simple test does not mean that an unbiased (unrelated to quiescence ;)) yet careful listener will not perceive a change.


Widget Sorry, I've clearly read more into your comment than I should have.

[Ian Mackenzie]

Gasfan,

Can you kindly describe how to how you went about your measurment and adjustment?

[DavidF]

There is a lot of thought put in the posts about acuity of response deviations and this device as a possible tool to confirm differences in what we hear.

I may have missed the point somewhere, but this device appears to provide objective evidence of a change in response, presumably due to differences introduced into the component chain somewhere. But, it does not delve into the possible reasons for the audible differences other than objectively confirm that they don't match up. So if there remains an audible difference, then it still leaves it to the user to determine, subjectively, which component chain provides the "better" result.

The device may be valuable in determining deviations from a known standard, perhaps. On the other hand, can't say it does much to avoid the objective/subjective contretemps.

[gasfan]

Gasfan,

Can yoy kindly describe how to how you went about your measurment and adjustment?

Sure. Standard procedure on Perreaux 2150B, Acoustat TNT200 and 120...current across rail fuse(remove fuse), same on various BJT amps...volts across emitter. On BJTs, if the sum of all outputs are lower than 150ma per ch., I'll turn it up first. My only experience with fets are the ones mentioned and they're up pretty high already. Once It looks like both channels are identical, pop the fuse back in if it's a fet amp, put music on and listen for a while. From experience I know regardless which channel I choose to adjust, if I need to turn it up or down. I always choose the R channel to match to the other because I'm right handed. On my knees exactly between the speakers about 2 feet back, amp in front of me on the floor. Carefully place precision screw driver on the pot and very slowly nudge it either forward or back, almost no movement. This with a 25 turn Bourns pot. 1 turn pots are not impossible but haphazard at best. I always replace them with Bourns multi-turn. Up close, on success, what you hear is a remarkable change in linearity. Cymbals all of a sudden ring like bells, vocals lose all indication of sibilance, bottom end finds another octave with sharp definition. That's when I know I'm there. Go to my listening chair while the pot settles and stabilizes, maybe a few tunes or so. Strong phantom center channel with great depth and pin-point imaging. Go back and tweak it again. But this time a tiny bit of an extra nudge in the direction it fell back from. And so on (I may have gone too far). It will either drift toward equilibrium or away. When I'm happy with it I'll leave it alone for a while. The following day it may sound even better:bouncy:. I leave it on 24/7. In any case, it's addictive and I love tinkering so I'm going to tweak it again by about a week or so. Sometimes to detriment recognizing it was dead on. The 1/10 mv tolerance is a guesstimate but I think a good one borne of my experience setting it initially with my dvm. It's commensurate with how much movement takes place while listening. Coincidentally, my newly acquired Citation XX calls for a 1/10th mv tolerance in the manual. I have not yet worn out a pot.

[Ducatista47]

There is a lot of thought put in the posts about acuity of response deviations and this device as a possible tool to confirm differences in what we hear.

I may have missed the point somewhere, but this device appears to provide objective evidence of a change in response, presumably due to differences introduced into the component chain somewhere. But, it does not delve into the possible reasons for the audible differences other than objectively confirm that they don't match up. So if there remains an audible difference, then it still leaves it to the user to determine, subjectively, which component chain provides the "better" result.

The device may be valuable in determining deviations from a known standard, perhaps. On the other hand, can't say it does much to avoid the objective/subjective contretemps.
The simplest intent was to change a component (macro, an amp for instance or a cable or an element of a room treatment, or micro, a resistor or cap again for instance) and discover if the change did indeed make a difference, or did not. The tool obviously also could have other uses, but it seemed to me that was the genesis of the software. Record, make a single change, record again and run the software. There is no guesswork what happened and where because there was only one change. If there is a change the audio level involved can be determined, so the question of audibility is also addressed.

"Better" is completely subjective and does not enter into it. That said, subjective evaluations of gear become moot if the gear is proved to do nothing at all. If someone thinks it improves things anyway, psychoacoustics, expectation bias and all the rest enter the conversation and science and engineering exit the discussion, and in my experience exit the entire premises and seek a home elsewhere.

[Ian Mackenzie]

Okay

Now l get it.

Seems you are listening to the 1st watt or so and that is going to be case for those things you are listening for.

There is some consensus that the 1st watt is critical and in theory the spectrum of thd may vary with adjustment.

This amp like the one you have at 1 watt is the hardest ask of all as the amp is more linear at 100 watts.

It hard to say but it could be a null of certain harmonics and if you don't have that in both channel it might be a blur.

This is based on premise that in multi stage amps different stages have different harmonics of thd and on a fluke the next or preceding stage will cancel out a distortions node or add which could be a good thing.

Pass has done empirical research on spectra of distortions on he talks about it in his articles and there is an interesting article called the sweet spot that goes deep into the operating curves of the devices themselves and the newer point 8 Amps are not generic but each tuned as stand alone designs.

Being pragmatic unless it was Pass amp l sincerely doubt the manufacturer would bother with it but for you it's like blue printing a racing cam in a motor and it runs as smooth as silk up to redline.

While l have no doubt of your adjustments if it was respectfully adjusted by a friend and you were blind folded l wonder if you would be saying have you made the adjustment ?

If you could set up an array of test gear and a group of listeners and do some adjustments with a double blind test and gets survey of results supporting the claim you might write a paper and publish it in the AES.

I say this respectfully as placebo or listening with your eyes is a proven logic where the brain visual cortex tells the brain like a "yes man" thing that overrides reality because it was visual and acknowledged and we therefore hear a difference. Floyd has documented this at JBL with engineers and the engineers got it wrong when compared to a double blind test (the wankers..,Lol.)

I know myself if a test a bunch of j fets and match the Ids l know because l did that or if a tweak the bias it will be better!

So while there is some consensus to avoid being boo who'd a double blind test with a friend would be a good idea.

I mean about 20 years ago a friend came over with $800 interconnects.

We put them on and he instantly said it was better and we said yes so he would not loose his shit.

He then went out for a cup of tea and we swapped it back.

I asked him to describe what was better then about the cables that he could hear.

He told me and l then told him it was the original cable.

He seriously lost his shit and said l was mean and a bastard (a pita).

But this is what happens when the roof caves in on the Church.

Getting back to Mr Widget post there are people like Burson Labs in Aust who now market upgrade opamps for not a lot of money.

The reviews are promising but is this placebo or actual fact?

Then there are long time advocates of pro opamps like the 990 designed by Deane Jensen in 1979 found in mixing desks that have been around for over 20 years because they have a certain tone that engineers like.


http://www.johnhardyco.com/pdf/990.pdf

The we have more moden opamps like this one has has rave reviews. Why?

http://www.tnt-audio.com/accessories/sparkos_ss3602_e.html

Esteemed Audio legend Mark Levinson came up with a way of using particularly rare semi-conductors in products 40years ago that are now public knowledge and in the Hall of Audio Fame. The ideas are now not unique but difficult to implement in production without a price tag.

The designs used a particular approach to symmetry and matched parts that some say resulted in clarity and unmatched sound stage.

All I can say is that in the shop that sold the stuff locally 40 years ago the reps said there was no comparison.

Only when the Ampzilla came out from GAS by the late James Bongiorna (previously of SAE) was there an alternative to SS hi end.

I still have all the parts somewhere from the article in Popular Electronics.

Then there was Threshold by a young Nelson Pass (who was previously working for ESS Loudspeakers (Dr Heil) ) and more recently First Watt.

All these people were/are very gifted technically, they listen to what they are doing and are good a turning a brilliant design into a commercial reality. The latter is still going from strength to strength based on recent reviews and media releases (F7).

So when we talk about sound differences in audio its can't be all bullshit.

[gasfan]

Okay

Now l get it.

Seems you are listening to the 1st watt or so and that is going to be case for those things you are listening for.

There is some consensus that the 1st watt is critical and in theory the spectrum of thd may vary with adjustment.

This amp like the one you have at 1 watt is the hardest ask of all as the amp is more linear at 100 watts.

It hard to say but it could be a null of certain harmonics and if you don't have that in both channel it might be a blur.

This is based on premise that in multi stage amps different stages have different harmonics of thd and on a fluke the next or preceding stage will cancel out a distortions node or add which could be a good thing.

Pass has done empirical research on spectra of distortions on he talks about it in his articles and there is an interesting article called the sweet spot that goes deep into the operating curves of the devices themselves and the newer point 8 Amps are not generic but each tuned as stand alone designs.

Being pragmatic unless it was Pass amp l sincerely doubt the manufacturer would bother with it but for you it's like blue printing a racing cam in a motor and it runs as smooth as silk up to redline.

While l have no doubt of your adjustments if it was respectfully adjusted by a friend and you were blind folded l wonder if you would be saying have you made the adjustment ?

If you could set up an array of test gear and a group of listeners and do some adjustments with a double blind test and gets survey of results supporting the claim you might write a paper and publish it in the AES.

I say this respectfully as placebo or listening with your eyes is a proven logic where the brain visual cortex tells the brain like a "yes man" thing that overrides reality because it was visual and acknowledged and we therefore hear a difference. Floyd has documented this at JBL with engineers and the engineers got it wrong when compared to a double blind test (the wankers..,Lol.)

I know myself if a test a bunch of j fets and match the Ids l know because l did that or if a tweak the bias it will be better!

So while there is some consensus to avoid being boo who'd a double blind test with a friend would be a good idea.

I mean about 20 years ago a friend came over with $800 interconnects.

We put them on and he instantly said it was better and we said yes so he would not loose his shit.

He then went out for a cup of tea and we swapped it back.

I asked him to describe what was better then about the cables that he could hear.

He told me and l then told him it was the original cable.

He seriously lost his shit and said l was mean and a bastard (a pita).

But this is what happens when the roof caves in on the Church.

Getting back to Mr Widget post there are people like Burson Labs in Aust who now market upgrade opamps for not a lot of money.

The reviews are promising but is this placebo or actual fact?

Then there are long time advocates of pro opamps like the 990 designed by Deane Jensen in 1979 found in mixing desks that have been around for over 20 years because they have a certain tone that engineers like.


http://www.johnhardyco.com/pdf/990.pdf

The we have more moden opamps like this one has has rave reviews. Why?

http://www.tnt-audio.com/accessories/sparkos_ss3602_e.html

Esteemed Audio legend Mark Levinson came up with a way of using particularly rare semi-conductors in products 40years ago that are now public knowledge and in the Hall of Audio Fame. The ideas are now not unique but difficult to implement in production without a price tag.

The designs used a particular approach to symmetry and matched parts that some say resulted in clarity and unmatched sound stage.

All I can say is that in the shop that sold the stuff locally 40 years ago the reps said there was no comparison.

Only when the Ampzilla came out from GAS by the late James Bongiorna (previously of SAE) was there an alternative to SS hi end.

I still have all the parts somewhere from the article in Popular Electronics.

Then there was Threshold by a young Nelson Pass (who was previously working for ESS Loudspeakers (Dr Heil) ) and more recently First Watt.

All these people were/are very gifted technically, they listen to what they are doing and are good a turning a brilliant design into a commercial reality. The latter is still going from strength to strength based on recent reviews and media releases (F7).

So when we talk about sound differences in audio its can't be all bullshit.

Right. It's always about the first watt. But I don't think ABX is necessary for this or even possible since it's always about the amp in question. OTOH, if before and after recordings at the listening position were taken, they could then be used. The other way is simply listening for the transition behind a curtain.

[Ian Mackenzie]

Behind the curtain is essentially a blind test

yes another identical amp or a switch of pre and aft bias adjustment would work.

If there person flicking the switch has no idea what way was what and the listener was not told dush
then that would be a double blind test.

My point is that if an ordinary person or group who listen to hi fi could not discern a difference one way or the other behind the curtain with no incling of which change was being made then you have fact beyond reasonable doubt that there is a difference.

Then it's a case of getting a vote on preference.

I will never forget the first time l heard Hugh Dean of Aspen amps demo his Life Force amp in the mid 90's and tell everyone why is sounded so good.

When l heard it l privately l thought it was so so and somewhat coloured.

He had a Picasso approach to amp design early on and got better and in the end enjoyed world wide acclaim but only after accepting honest feedback from audiences at demos and including Mouser part numbers on the schematic parts list. (Kent English at Pass labs had one which is an interesting bit of trivia).

Sometime later Hugh suggested a power transistor upgrade for my JLH 15 watt class A amp.

The 2N3055 would blow too easily as my heat sinks for only just big enough. The new transistor were Sanken and yet it was marginally better.

That was and still is one of the best small amps period. This amp is so clean and clear it makes you stop and listen.
It was originally designed by the late John L Hood to mimic the Williamson Valve amp.

The article first appeared in the Wireless a World magazine in the late 60's.

[gasfan]

Behind the curtain is essentially a blind test

yes another identical amp or a switch of pre and aft bias adjustment would work.

If there person flicking the switch has no idea what way was what and the listener was not told dush
then that would be a double blind test.

My point is that if an ordinary person or group who listen to hi fi could not discern a difference one way or the other behind the curtain with no incling of which change was being made then you have fact beyond reasonable doubt that there is a difference.

Then it's a case of getting a vote on preference.

I will never forget the first time l heard Hugh Dean of Aspen amps demo his Life Force amp in the mid 90's and tell everyone why is sounded so good.

When l heard it l privately l thought it was so so and somewhat coloured.

He had a Picasso approach to amp design early on and got better and in the end enjoyed world wide acclaim but only after accepting honest feedback from audiences at demos and including Mouser part numbers on the schematic parts list. (Kent English at Pass labs had one which is an interesting bit of trivia).

Sometime later Hugh suggested a power transistor upgrade for my JLH 15 watt class A amp.

The 2N3055 would blow too easily as my heat sinks for only just big enough. The new transistor were Sanken and yet it was marginally better.

That was and still is one of the best small amps period. This amp is so clean and clear it makes you stop and listen.
It was originally designed by the late John L Hood to mimic the Williamson Valve amp.

The article first appeared in the Wireless a World magazine in the late 60's.

I better get myself in trouble before it's too late. I think the main thrust of my argument has been lost in the shuffle here. My contention is that there is no or negligible stereophonic effect without this 'tweak' if you will. Or unless signal levels are absolutely precise. Using just amplitude to position a sound source between two speakers is not stereo. I'm asserting that the vast majority are listening to gear that is not functioning as it should/could as per design. I believe it's phase distortion which should easily be measurable. So I think it's important enough that virtually anyone would be able to discern a difference. Unless the likes of Douglas Self and Nelson Pass have paid attention to this, I believe it's yet to be discovered. A lot of attention has been given to holding bias at precise levels by various means but I'm saying the tolerances have been far too wide.

Incidentally, I'll add that the so called 'edginess and brightness' attributed to ss by the tube guys lives in this bias mismatch. When things are optimal, it disappears. That's when ABX spanks the tube amps for sure.

[Ian Mackenzie]

Well thats absolutely fine.

Audio re production in the domestic sense is highly subjective by its very nature and we are all entitled to our views on what we hear or don't hear in our own homes.

[gasfan]

Alright sir.

[1audiohack]

Hi All!

I was thinking about this thread yesterday morning when preparing for the audio club meeting a couple of us ran a comparison of four MM phono preamps. These pre's have made the rounds between members of the club but I missed all of that somehow. What everybody involved said however is that they all sound different, and the like order is not consistant system to system. Hmmm.

Me being an objectivist I wanted to measure them first. Usually I like to listen first and then see if I can measure what I hear, if I can hear a differences. If I can't hear a difference, measurment is just academic but we didn't have a lot of time and didn't want to turn the meeting into an experiment session, plus I hate clutter so I wanted what ever was not going to be used out of the room before the guests came.

The quick and dirty way was a TEF magnitude and phase shot. Now, I don't have previouse experience measuring phono stages and dont know how they respond to being driven with a low impedance source. I drove them with 0.01V from 24kHz down through zero and back to 200Hz in an attempt to get good LF resolution. I also wish I would have had a better cable to drive them with. :(

All had zero latency so no digital anything hidden in the little black boxes and all very nicely fit the standard RIAA eq curve, really within about +-1dBV and all had equal phase behavior. Three had virtually the same gain and the exotic had a full 3dB more. The exotic also had the most deviation from the RIAA standard.

We hit my Sony pre, an SAE pre, a home built pre and some exotic thing with a feminine name that I would have to look at my test note to remember.

In use as it turns out, all of them were quiet, the Sony and SAE sounded identical to me, the DIY unit was pretty close and the high gain exotic absolutely fell apart with loud complex piano content. Now it is possible that is was overdriving my preamp but the input overload light never flickered.

So, as many have said, a frequency sweep is not the end all measurment. It would also seem that a lot of what were the perceived differences in other subjective tests may likely have been level skewed.

I wish I had a good IM distrtion tester. I also don't believe swept sine is the most demanding test signal and my scope was at the shop.

If I had this to do over again with test equipment that I own I think I would also hit these with MLSSA. The semi random noise may be more telling and I certainly would have looked at harmonic distortion. I didn't even think to hit them with a square wave and look at stability.

This would have been an interesting thing to run through the Audio Diffmaker. Would it find it? This is where I think this type of test may really shine if it has the ability to resolve differences with complex test signals, like music. Imagine being able to use a drum track or a piano track with varying level, through varying equipment, being able to mormalize the level and hear whats different. Wouldn't it be interesting to hear just the distortion components of a piece of equipment subject to small and large drive levels? With the level normalized, what would we hear?

Clark I hope this isn't deemed to be a derailment to your thread, rather a continuation of the disscussion on how do we better measure what we hear?

I hope to explore this more in the near future.

All the best,
Barry.

[Ian Mackenzie]

Edited


Hi Barry

Thank you for the insights.

Phono stages are one of the most difficult to design and measure as far as amplification is concerned.

In the test reports on some of the better audio magazines the resolution per division is 0.2 db for the frequency response loading from an inverse riaa source generator.

Some phono amp curves look like bananas!

Technically and objectively the effect of subtle (to the eye variations) variations on the overall response measurement are in fact extremely important to the subjective assessment.

Theses variations from a dead flat response are according to experienced professionals a major reason for shifts in tonal balance

You may think this is crap. But in terms of wide band flatness unlike narrow dips or peaks the ear / brain can evaluate subjective response variation such as a self response lift or boost below 100 hertz of +0.25 db and a shelf response cut of -0.25 db above 1000 hertz.

The total variation is 0.5 db but it is not in a narrow spectrum but in broad areas where the ear / brain is quite sensitive to change below 100 hertz and above 1000 hertz.

If you have a loudness button on your amp it's like a subtle version of that.

Under resolution of -+ 0.2 Db per division variation of more than 0.25 db +- is considered audible across the entire audible spectrum of 20-20,000 Hz. This is documented.

It is subtle but once you start to play a selection of Lps the ear/brain recalibrates and re learns and stores in like memory was it going.

If then, unexpectedly the calibration is no longer accurate from what is learnt and stored a light bulb goes off in your head as a heads up that there s a difference.

The question is then when is flat really flat?

The other issue with MM phono stages is cartridge intereaction with the input of the phono circuit.

This is due to the inductance of the cartridge interacting with the workings of some types of phono circuits.

Most MM phono cartridges are not actually flat and rely on some form of loading to optimise the response with some capacitance and this is trial an error by the user if the preamp has loading options.

Some phono stages have a de emphasis from what might be termed the official riaa curve and they can also account for response variations.

One phono stage called the iPhono has a number of built in curves that can be selected.

Then there is overload margin. The effect of a low over load margin (35 db is regarded as a minimum overload margin) is distortion, a lack of dynamic range or congestion in complex program material.)

Non of this is trivial for phono stage performance.

Back to the audio diff maker if it has the above resolution it maybe useful.

[Mitchco]

Hi All!

...


This would have been an interesting thing to run through the Audio Diffmaker. Would it find it? This is where I think this type of test may really shine if it has the ability to resolve differences with complex test signals, like music. Imagine being able to use a drum track or a piano track with varying level, through varying equipment, being able to mormalize the level and hear whats different. Wouldn't it be interesting to hear just the distortion components of a piece of equipment subject to small and large drive levels? With the level normalized, what would we hear?


All the best,
Barry.

Check out the links posted: http://www.audioheritage.org/vbulletin/showthread.php?38140-Audio-DiffMaker&p=389822&viewfull=1#post389822

I hope folks give it a try. Listening to the difference file, that uses music as the test signal, is educational to one's ears.

Kind regards, Mitch