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since new topics here in Geek Central seem to be few and far between.......I was wondering what ideas some people may have relative to quantifying small changes in sound quality, or, less subjectively, system response. Since the topic is complex (and controversial) enough already, let's avoid speaker/room interactions and just discuss measuring electrical signals (the signal may be measured at different places in the signal chain depending on the goal of the measurement), and let's only measure unamplified signals for now to make it even easier.
I'm not interested in discussing DBTs or other testing methods using humans as the detection device. In this thread I'd like people to stay focused on using devices to measure differences in system response. The goal isn't to figure out if 'Component A' sounds better than 'Component B'. The goal is merely to determine that there is or is not a difference between A and B, and hopefully some indication of how large the difference is.
To give everyone a starting point, I'll propose a method that is likely very flawed (please forgive my ignorance if this has been proposed before). With any luck, the process of pointing out the flaws in my proposal will lead to some better ideas, and maybe even a method that eventually becomes reliable and accepted. Keep in mind that I'll be assuming any tests will be conducted scientifically, using the best methods possible to reduce potential errors or inconsistencies - in other words, I'll be omitting some of the details that are necessary to achieve precision and accuracy in the spirit of simplicity.
Start with a high quality digital recorder. Given that this exercise has no budget, we'll use either a DSD recorder or a 24/192 PCM recorder. Hook the recorder up as far upstream in the system as possible so that the recorder is connected to the output of the device in question. Now start recording samples of your reference material - you'll obviously want a digital source of the same format as your recorder, and it should be a complex music signal - no pure sine waves or square waves. Record lots of samples, because I'm sure no two samples of the same clip will be recorded exactly the same due to vibration and a slough of other factors.
Once you have enough samples, you can compare the samples to one another, and also to the source. If there's too much variation, you can stop testing and start thinking of a better way to do this. If you find a fair amount of consistency among your samples, then average the samples together. The difference between the average of your samples and the source is a rough gauge for your system's baseline distortion, including the recording device, of course.
Now, switch out the component and record the same number of samples you did in part 1. Now compare the averages of the two sets of samples. Are the averages different? If so, there's likely a difference in system response. How big is the difference compared to the baseline distortion?
Once again, this has probably been explored before and probably won't work, but why won't this work?
-Pete
Follow Ups:
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Clark is right, cut the fuss, and just listen with the HIGHEST quality source that you have. Keep the levels and the absolute polarity right, then listen, and compare. If you want, just name the components L and M or something like that. You can keep score like this as well, but don't revert to a compromised source, such as a DAT, or even a cheap CD or DVD. Use the best that you have: Clean CD's with really good playback, analog tape, if you have it, or vinyl records. SACD and quality DVD (A) might give enough, but look at the playback compromises in the digital playback equipment for potential limitations.
Thanks for your input, John. Please let me try again if I fumbled on the first attempt...If you look at other posts of mine, you'll see that I'm a proponent of listening to things to both quantify and qualify small changes in sonic performance, rather than writing off small differences as imaginary simply becuase no one has yet figured out how to measure the subtle things that humans can hear. Cables are a perfect example of this. The whole reason we have yeasayers and neasayers is because there is no widely accepted method for measuring with devices other than humans.
Like you, I know what I hear, and I don't need any measurements to tell me what I hear. I'm definitely not claiming that I can hear all that can be measured (and thus the value of measurements), but I'm definitely claiming that I can hear things which we don't yet know how to accurately measure.
I suppose some may see the aim of this thread as something that would end up taking some of the art out of designing a new component or assembling a fine sounding system, but I don't think that would ever happen, regardless of how far audio science happens to advance. Look at the automotive hobbyists for a good example of this. Making big horsepower with high volumetric efficiency is very much a science these days, and while there's no shortage of guys putting turbos, intercoolers, custom programming, a wing and a fart pipe on a Civic, it's not hard to find guys who'll still throw a carbureted big block into a '76 Vega - both guys are gonna have fast cars, but they achieve the results in very different ways (and other than both being fast, both will have very, very different characteristics that you love, hate, or perhaps don't even notice depending on your taste and senses).
I'm off to listen to music until I fall asleep now, but if anyone has any ideas how I can produce some measurements that will prove to people that I'm not crazy when I claim I hear a significant difference between two cables, please do chime in.
"Making big horsepower with high volumetric efficiency is very much a science these days..."If this is really the case can you please explain why the winner of Popular Hot Rodding's Engine Masters Small Block Challenge was 61 year old Joe Sherman ? When Joe Sherman was asked at the 13th Annual Advanced Engine Technology Conference which engine modeling software he used to develop his challenge winning engine his answer was:
"What is that?"
Engine Masters Annual 2003 Volume 6 No. 1Page 33:
"While Joe knows the software exists, he relies on the wealth of experience that he's gained in order to design performance engines to suit specific needs."
jon banquer
you're actually reinforcing my point.You've cited an example of an old guy working with old technology and getting good results, despite the fact that it's possible to achive the same thing using new technology and computer modeling.
In case you're confused, the small block V8 is ancient technology. Anyone working with a small block motor has the benefit of several decades of trial and error, which is in itself science (science does not require a computer). Read up on the LS1/LS6 engine if you're not already familiar with them. If you don't think designing those motors was way more sceince than art, you should be visiting a different type of asylum.
So, you've reinforced my point that regardless of technological advances, there will always be an element of art involved with audio engineering. It will always be possible to design and build top notch gear using old methods.
-Pete
PS - I didn't read the Popular Hot Rodding article, but what are the chances the cam Sherman decided to use was NOT designed on a computer? Probably slim....
> you're actually reinforcing my point.No, what I did was refute your assertion with fact. Those
facts did not register with you so I'm going to provide even
more facts in an attempt to show you how incorrect you are
with your assumptions about "new technology" and "computer
modeling"
> You've cited an example of an old guy working with old
> technology and getting good results, despite the fact that
> it's possible to archive the same thing using new technology
> and computer modeling."LOL.
The FACT is that the "old guy" working with "old technology"
beat those using engine computer modeling technology and
beat many of them very badly. He did it because there is no
engine computer modeling software at the moment that can
beat or even come close to Joe Sherman's many years of
experience.Lets take a look at what Joe Sherman was able to do in a
competition designed to produce a *streetable* pushrod small
block running on pump gas.Engine Masters Annual 2003 Volume 6 No.1
Page 82:
Dyno results:
Average Torque: 482
Average Horsepower: 421.6
Peak HP: 604.1 @ 6,500 RPM
Peak Torque: 528 @ 5,100 RPM"Building a small block Chevy in not rocket science but
tuning one to this level approaches aerospace finesse"> In case you're confused, the small block V8 is ancient
> technology.I'm not confused but you certainly are. Just because you
have something like dual overhead cams and four valves per
cylinder does not mean that a push rod, cam in block engine
is "ancient technology". If it was "ancient technology" then
can you explain how GM is able to produce *more power for
less money* from a push rod, cam in block engine than Lotus
was able to create with their state of the art 32 valve
dual overhead cam V8. Lotus designed the LT5 engine and it
was built by Mercury Marine. This subject is covered at
length in Dave McLellan's.(former chief engineer for the
Corverte) book. If Dave McLellan feels that the pushrod cam
in block Chevy V8 has plenty of development left in it, and
that it's by no means what you label "ancient technology"
why in the world would someone except your premise that
it is ?Here is a link to Dave McLellan's superb book.
http://www.bentleypublishers.com/product.htm?code=gcmc
I'll leave you with one more example of someone who used the
pushrod cam in block Chevy V8 as the basis for his very
successful V12.http://www.falconerengines.com/ryan_bio.htm
"The '80s also saw the first ever turbocharged V-6 at the
Indianapolis Motor Speedway, built by Falconer. In IMSA,
Ryan Falconer was a major contributor in the development of
Chevrolet's GTP corvette program. He provided 1200
horsepower for the Hendrick Motorsports Corvette in the form
of a 3-liter, single-turbocharged Chevy V-6. The engine was
a force to be reckoned with, competing against and beating
Europe's best factory-backed efforts from BMW, Porsche and
Jaguar"http://www.corvette.co.uk/gtp.html
"Later at the hand of Ryan Falconer, no relation, peak
output was pushed to over 1100 bhp. Chevrolet thinking then
was that big engines were finished and that the V6 would
take over from the Small Block which would be out of
production by 1990. How wonderfully wrong they were !"IMO the GTP Corvette won despite the handicap of having a
horrible Lola chassis and unreliable GM experimental
electronics. I personally watched this car being driven by
Serel Vandermerwere and talked to Serel about it at length
(over an hour) at Lime Rock Park, CT and at Riverside,CA.
The car could easily lap Porsche 962's. Thank god for
Porsche that GM never got serious because it would not have
been pretty.> So, you've reinforced my point that regardless of technological
> advances, there will always be an element of art involved with
> audio engineering"In my mind the "element of art" in regards to internal
combustion engines can be better stated as experience
and mechanical aptitude.As far as audio is concerned, all I have is opinion and personal
observations and a technical forum like this does not seem to be
the place for my opinions or personal observations in regards to
audio.Thanks for the opportunity to debate with you the merits of what or
what is not "obsolete technology" and what current engine modeling
software can and cannot do.
jon
The LS1/LS6 motors, the only newer newer technology I mentioned in my previous post, are pushrod, cam-in-block motors.The Chevy Small Block is a specific type of block that's been around since at least the 1950's. It was a great design and can still support some monster power.
Obsolete was your word, certainly not mine.
I drive a car that has a pushrod V8.
"Obsolete was your word, certainly not mine."Yup. My mistake. You did not use the world "obsolete".
You used "old technology" and I obviously think "old
technology" is a very misleading term in this case.I would be comfortable discussing the LS1 small block should
you so desire. I don't know enough about the LS 6 as it's
to new a motor for someone like HP Books or Cartech (SA
Design) to have written a rebuild / high performance manual
on.In case were accused of being off topic by the moderator can
we agree to claim that our discussion is on topic because
what we are really getting at is how these engines sound. ;> )
jon
In the interest of clarity for those not familiar with
Corvette history, I should have mentioned that the Lotus
designed state of the art 32 valve dual overhead cam V8 LT5
engine, that was built by Mercury Marine, was used in the
ZR-1 Corvette.
due to all the arguments put up by Steve Eddy, but John Curl has found measurable differences between cables. Now that Steve Eddy is gone from AA, maybe John can discuss it without being hassled to death. Or, you could probably just search the archives (although it would be pretty painful to go through all the arguments!).
Went over to John's last weekend, and we took a look at some of those measurements (and measured my Purist Colossus IC)The question of whether John's measurement rig is flawed has been beaten to death, but here's what I saw:
We exchanged 4 or 5 different kinds of cable, all RCA terminated, and each cable exhibited 2 things:
1) A different pattern of harmonics of the original signal that was perfectly repeatable; we could exchange the cables back and forth and always get the same spectrum for a given cable. Some of the spectra included significant amounts of 8th - 10th harmonics.
2) A different pattern of noise (i.e. signals at frequencies unrelated to the original) that was also repeatable. Obviously, the shielding ability of the cables is different.
The repeatability of the tests makes me believe that the harmonic spectrum is not due to connector issues on the test setup, as was suggested in an earlier post, although I suppose you could always argue that the complex comination of distortion analyzer, RCA adapters and spectrum analyzer creates the signature, rather than just the cable. Sounds like what happens in a real audio system to me...
John's test set up is actually quite straight forward, and not all that hard to duplicate, so I'm mystified by the fact that so many people have foamed at the mouth about it, but none have tried it.
It's also interesting that nobody has been able to explain the results, prefering to shoot the messenger.
""It's also interesting that nobody has been able to explain the results, prefering to shoot the messenger.""PeterIt is not for lack of trying, at least for me..
Just search the archives for my post on "peltier or seebeck", or John's response to that post by searching for "bull shit".
I've seen people "shoot the messenger" only after John takes a whack at them first..
""although I suppose you could always argue that the complex comination of distortion analyzer, RCA adapters and spectrum analyzer creates the signature, rather than just the cable. ""peter
That is of course possible, but since no efforts to determine that have been undertaken, one will never know.
""Sounds like what happens in a real audio system to me...""peter
Absolutely..but, until the source is truly characterized, real audio system mods will always remain haphazard and full of really ridiculous theories and explanations..
I don't believe all the "heard effects" are imaginary; I just see very little science applied to finding the root cause.
Thanks for the info..
Cheers, John
Ok, I agree with:I don't believe all the "heard effects" are imaginary; I just see very little science applied to finding the root cause
I also see a lot of head-in-the-sand denial from many people here (not you).
I think it's great that you want uncover the real physical causes of these effects. I think your obvious expertise could be used more constructively to help further this understanding, rather than being used purely to prove that nobody else knows what they're doing.
Yeah, John C's not always the easiest person to talk to, and he certainly has a short fuse, but that doesn't invalidate what he's done. At least he's doing something.
There have been a large number of posts in which you push on John to get more details about his test set up. This is a joke to anyone who understands the test equipment involved, but looks impressive to some people here.
Given how simple the measurement is, it's clear that you are not seeking information so that you can duplicate the test (that would be real peer review), but so that you can show the rest of the board how smart you are by finding holes in his methodology. Oh, and you don't have to be right; you just have to sound right...
I described the test set up in another message. If you set up a similar environment, made some tests, and got different results from John's, THEN your critique of his set up might be useful in moving the science forward.
Until then, it's 100% hot air. You could contribute a lot more.
""This is a joke to anyone who understands the test equipment involved""peterPerhaps...but I do not know the equipment, so if I don't ask, I don't learn. And, I've been unable to get the manuals for JC's test gear for my learning...
""Given how simple the measurement is, it's clear that you are not seeking information so that you can duplicate the test (that would be real peer review), but so that you can show the rest of the board how smart you are by finding holes in his methodology. ""peter
see my post below...it's not that easy..
And I've no desire to perform the exact same test using the exact same equipment in the exact same way if something fundamental to the setup is producing the results. Finding the same results with a completely different setup is FAR more valid.
I did go back and look at the threads you referenced, and I saw lots of miscommunication in all directions.... Pity, given the potential value of real communication.Somehow John and SE got into this bizarre thread concerning gain of a mac sound card, which as far as I know has nothing to do with the test...
So, here's what I saw at JC's:
Sound Tech 1700B (modified) acting as oscillator. Signal fed into cable under test. Output of cable goes into 1700B to null out the fundamental. Residual output of 1700B (minus the fundamental) sent to two spectrum analyzers. One is an old HP3580, the other is (from memory) an HP3563. The main difference is that the 3563 completes a measurement in much less time. The results were plainly visible on both scopes. The 3580 showed almost as much detail as the 3563. It just takes longer to do the measurements. The 3580 has a dynamic range of about 80dB, but of course we were starting way below the amplitude of the fundamental since we were looking at the distortion residuals.
I just bought a used 3580 on eBay for $300; don't know its condition yet... I'm not that concerned about its absolute calibration state, since my primary interest is in looking at the shape of the distortion spectra of equipment I build, rather than the exact magnitudes.
Good for you, Peter. We might have to work on your HP 331(I think) to get it lower in distortion, but what the heck. First of all, we should try to get schematics for your 331. By the way, I have the full book on the HP 3580 and you can borrow it, if you wish. This can be fun. We can also make an M-derived notch-low pass filter on your oscillator output with quality, (I hope) passive parts to reduce any residual, especially higher order, to almost nothing.
By the way, if you can find some Seebeck or Peltier effects, I would be glad to address it.
I'm not sure how the effects would manifest themselves.. Perhaps some kind of heat transport mechanism in one direction of current, and then most of the heat returning when current reverses..I wouldn't expect 100 percent efficiency in both directions, so any losses would show as distortion.At audio frequencies, any heat transport would be limited to perhaps 10 to 100 microinches (that's a WAG for sure) because of the thermal diffusivity involved. But that would be the range of a lot of platings..and definitely the copper tin intermetallic layers of the solder joints, if any.
That's why I'm interested in eliminating any other potential error sources.
Once again, this is bullshit.
""Once again, this is bullshit""John CurlThe fact that you are unable to understand the concept does not make it so. Nor does your repeated statements to that effect.
I thought your degree was in physics..so I really don't understand why you cannot follow the line of reasoning. Perhaps it's too theoretical for you?
The effect is used both for heating and cooling. It is reversible. And, as all typical processes, is not a perfect one. But it is something which is available off the shelf..
You show your ignorance with those type of remarks..I had hoped for better from you.
I am not going to put up with this crap, anymore.
Jneutron, if you have ANY possible evidence that the 'Seebeck Effect' could have ANYTHING to do with my measurements, then bring it out! This is a DC effect of thermoelectric power generation. How could it be otherwise?
You might as well ask me if I am still beating my wife. The fact that I am not married, or living with anyone, shouldn't deter you. These questions of yours, on my measurements, are about as likely.
Of course, I looked up any evidence of thermoelectric effects, but I did not find any that applied. For the record, I used thermocouples in measurement of temperature virtually every hour of every working day for almost year, when I worked as a tech at Underwriters Laboratories in 1962. I had 2 years of engineering/physics behind me, at that time. I have some idea of how they work, the dissimiliar materials used and the fact that it is a continuous offset, not a sporadic one. How is this going to generate harmonic distortion about 5KHz, when I have an 18/oct 400 Hz filter installed?
This unfounded criticism of yours is typical of why many audio designers distrust 'referees' associated with the AES. But that is another story.
""I am not going to put up with this crap, anymore.""JCWhat crap? you have avoided a technical discussion of any kind..
""Jneutron, if you have ANY possible evidence that the 'Seebeck Effect' could have ANYTHING to do with my measurements, then bring it out! This is a DC effect of thermoelectric power generation. How could it be otherwise?""JC
Where to start??
Ok, get a peltier module..buy it somewhere.. Notice that it is capable of two way heat transfer..It's commercial stuff, everyone can get it..
It is possible to drive one with a bipolar current source..The current direction will determine the heat flow path..I was considering it for my heat controlled plate for my IA circuitry. By monitoring the setpoint vs actual, the bipolar drive can either cool or heat the plate..
The problem with that is the time constant of the assembly. It is very slow, and makes the circuit "breath", so to speak. And it causes horizontal gradients on the plate, and that is the thing I'm trying to avoid the most.
So, I am simply going to use some surface mount resistors to heat, put the assembly ten degreec C over room, then provide a controlled heat leak to the outside world.
Now as to our discussion??? Take the module, and apply a .01 hz signal to it.. Note the temperatures on each surface will track the current. Also note the I/V response of the device itself. It is not a pure resistor, it's non linear, and the hysteresis it shows is not unlike that of iron's, although a different storage and loss mechanism is at work..
Now, increase the drive frequency..You will notice that it's response will begin to roll off, that occuring when the speed of heat transport in conjunction with the the heat capacity (that relation is called diffusivity) prevents the thermal fronts from reaching the surfaces. There is still heat transport ocurring..it's just that the speed at which the heat flow occurs starts to become slow compared to the drive signal.But, if you look at the I/V characteristics even at high frequency, it is still there, and still non linear.
To make the device act at higher frequencies, it is necessary to either speed up the heat transport (cooling to cryogenic temperatures does that by decreasing the heat capacity of the materials w/r to thermal conductivity...copper heat capacity drops 3 orders of magnitude at 4K while retaining thermal conductivity), or decrease the physical dimensions of the device. Unfortunately, by doing that, the device efficiency decreases due to thermal conductivity of the device.
Now...All dissimilar metal interfaces show the effect to varying degrees. (( I believe the King of Sweden had a face to face with the person who showed that)). So, why would you make the assumption that plating or soldering or welding or crimping would prevent that process from occuring????
""These questions of yours, on my measurements, are about as likely.
Of course, I looked up any evidence of thermoelectric effects, but I did not find any that applied.""JCHmmmm..review what I have just posted, think about it, ask questions, or look it up...Rather than your glib remarks discounting it.
""For the record, I used thermocouples in measurement of temperature virtually every hour of every working day for almost year,""JC
For the record, so does my toaster oven..and it also demonstrates the same understanding of how they work..
""I have some idea of how they work, the dissimiliar materials used and the fact that it is a continuous offset, not a sporadic one. How is this going to generate harmonic distortion about 5KHz, when I have an 18/oct 400 Hz filter installed? ""JC
Hmmm..since dissimilar metals generate a non linear, temperature sensitive junction at some level, how can you ask that question??
""This unfounded criticism of yours is typical of why many audio designers distrust 'referees' associated with the AES. But that is another story. ""JC
If you go back and review every single solitary post I have put up regarding this effect, you would see that the only criticism I have stated is regarding your stupidity w/r to attitude and people skills.
You know, it is not necessary to post really stupid statements to get me to explain something..All you really have to do is ask..I'm more than happy to educate you in regard to things you don't know. As well as placing in public domain what I believe to be accurate so that my understanding can also be questioned. After all, we're all human and make mistakes..
Review everything I've said John.. I've not stated that the seebeck/peltier effect is causing what you are measuring..I initially asked you if you thought that it was a possible mechanism. To that, you glibly replied "bull shit".
If you are personally laughed at, discounted, ignored, by AES and other professional people, it is because of your own "people skills". Not because of their own ignorance..It's not the rest of the world, John....You make it clear it's you..
Cheers, John
Jneutron, I have suffered your jibes and insinuations for more than long enough. Just because you cloak it inside scientific platitudes, doesn't make it any more correct.
For the record, you have measured nothing in the audio realm to the best of my knowledge, and have little ability or inclination to do so. You have derided: Jon Risch, Dr. Hawksford, and me in the same way. You always throw out some 'scientific principle' that 'might' detract from our efforts, but you make no effort to show how it could, or whether it is an appropriate criticism. This just wastes our time, but I presume it makes you feel better in some way. Enough is enough.
""For the record, you have measured nothing in the audio realm to the best of my knowledge""JCYour "knowledge" being the key word here..
""You have derided: Jon Risch, Dr. Hawksford, and me in the same way.""JC
No, you are incorrect..
I have detailed Jon Risch's scientifically unsupportable theories..I have also lauded work of his that I consider very good.
Hawksford is a monster for DSP stuff, but has mixed waveguide theory with e/m propagation, and completely neglects dielectric discontinuity, power flow, and quite a bit more..Within the essex article, the most telling sentence is "now let's play for the gallery", then goes into speculation.
You stand alone in that regard..while they are logical, knowledgeable, right in many things, wrong in others...they at least remain civil..and will acknowledge they do not understand all, and demonstrate the ability to learn.
You choose to snipe at what I've posted, the actual science facts are ignored...you deflect all critisism of you by accusing others of the exact behaviour you are guilty of..
I await your technical discussion..I've seen none here..
If you wish to have a dialogue at the level you are showing here, goto www.toaster-oven.com, hit the link "buttered both sides".
My toaster oven at least keeps quiet when it doesn't understand a topic..rather than deflect the conversation in a dumb attempt at saving face. My ten year old stopped that 2 years ago..
Cheers, John
It is pointless to talk about Peltier effects, when there are no grounds for having them effect the measurement in some real way. It is up to YOU to show me where the Peltier effect or some other process can effect my measurements, when I am measuring with a 5KHz tone and have an 18dB/oct high pass filter at 400Hz inline, inside my test equipment. Talking technical at this level is unproductive, because your criticisms of my measurements, in this case, are groundless. Heck, I have a whole book on 'effects', should I list them where they 'might' have an effect somewhere with someone's measurement? It's just a waste of time and space.
It is not pointless.The discussion is to learn what we can...hypothesize what the effect, if any, would manifest as, and how it would present on an analyzer.
Your attitude is the waste of time..
I'm soldering 1000 joints with copper and tin, to allow measurements..while you "naysay" any possibilities..
If you wish to talk about "no grounds", try near superconducting, diode strand effects, TEM waves, 3 meter per second propagation...All stuff you spout..or cheer other on...but should I propose a possibility...You're all over me like stink on a skunk..
You gotta lighten up, listen to others, learn..
As you pointed out on the other thread...you learned something there...a discussion here would do the same for others.
in John's set up?So we've had the usual pseudo-technical pissing match.
Could we please now have a resonable suggestion where/how the thermocouple effects might appear?
In the test rig, there are obviously several connection points involving dissimilar metals. Given that there are small temperature variations across the rig, and JC's only looking at signals over 400Hz, can you describe what we should expect to see (or look for)?
Peter
I'm not looking for temperature variations across the rig..In fact, I'm trying to eliminate them in my IA setup, as metal films are 50 ppm/C.What I'm talking about is the non linear conversion of currents into heat flow..At audio frequencies, that heat flow will be unable to travel fast enough to modulate the surface temperature..But, the conversion process is still fast enough to react to an audio signal.
What I'm proposing is to measure the I/V characteristics of 1000 back to back solder joints, copper to tin/silver (only have a pot filled with that, not tin/lead.
The non linearity should be visible in the dc realm..If so, it should also affect ac. I figure 1000 joints should be enough that if there is an effect, it'll slap me upside the head.. If not, then an upper limit for that possibility could be established, something on the order of "not greater than 1 uVolt per joint", my rough estimate for dc simple measurements.
""So we've had the usual pseudo-technical pissing match.""Peter
Do not confuse what has been transpiring here as a technical anything. Regardless of how technical I have tried to keep it, it's not possible to have a one sided technical discussion.
If 1k joints have a 1 millivolt effect, JC's rig would see hash across the spectrum at levels totally unmistakable. Or, it may be that there is no effect...time will tell..
Oh sure, and when we change the cable to something else, the effects disappear. How does that happen? For the record, I have two different reference cables that don't significantly distort in my test. They are made by two different companies, and have two different metal compositions. They only share the fact that teflon is used as the insulator. Almost all other cables have specific higher order harmonics at low levels. Why? All I know, is that the test is repeatable with each specific cable, good or bad. Thermoelectric effects? Please show me how.
""Oh sure, and when we change the cable to something else, the effects disappear. How does that happen?""JCHmmmm...let's start with seebeck/peltier....If you look back at the work function coefficients, you will see that some metals have damn near the same numbers...copper, gold, and silver, for example..So cables using only those would have much less effect, than say tin, aluminum, nickel.. So, for Seebeck/peltier...you have to consider all the path interfaces.
Or, let's consider ground loop/shield resistance ratio..If the shield resistance is high, it will present a higher portion of loop intercept across the cable length, vs across the equipment ground..
""For the record, I have two different reference cables that don't significantly distort in my test. They are made by two different companies, and have two different metal compositions. They only share the fact that teflon is used as the insulator.""JC
For dielectric questions, I would defer to you and others, as I've not considered or worked with those issues..But, as I recall, I asked you if you had correlated the cable composition with the results...And your response was "I don't care what's causing it". And if you look at the work functions of the metals involved, you will see how some combinations of materials can look rather identical.
""Almost all other cables have specific higher order harmonics at low levels. Why? All I know, is that the test is repeatable with each specific cable, good or bad.""JC
And again...I have considered the fact that you have seen repeatable, cable specific differences in my thinking on the possible effects responsible.
""Thermoelectric effects? Please show me how.""JC
That is, of course, my intent to prove..it will either show yes or no..
But, having just a "tad" of experience at testing for things I would never have considered before, I refuse to be as glib as you when it comes to science and physics.
I will propose only scenario's and effects that can be tested for. Not hogwash..
We seem to differ in that respect.
John:There are lots of metal junctions in any system using an RCA-terminated interconnect, so perhaps there is an opportunity for thermoelectric effects. You just haven't described any yet.
Assuming that there is something here, can you postulate how you think those might show up? Can you suggest any likely effects that would show up in John's 400Hz - 50kHz measurement window?
If we can establish a hypothetical link between the Seeback/Peltier effects and what we are seeing on a spectrum analyzer, THEN it's worth pursuing this further and testing it. If not, what's the point of this discussion?
Any ideas?
I have tried, apparently with little success, to explain it..I'll try again..
""In 1821, Estonian-German physicist Seebeck demonstrated the electrical potential in the juncture-points of two dissimilar metals when there is a heat difference between the joints. This was the thermoelectric effect and is known as the Seebeck Effect in Physics.""
(copied shamelessly from:
http://chem.ch.huji.ac.il/~eugeniik/history/seebeck.htmlAs can be seen from this link, the efficiency of the device is a function between the electrical conductivity of the junction and the thermal conductivity of the materials.
http://www.uni-konstanz.de/physik/Jaeckle/papers/thermopower/node3.htmlThis link provides a slightly more technical version, and explains carnot efficiency and the such..keep in mind...a dissimilar metal junction with small currents will have low temp gradient, hence the carnot efficiency will be practically zero..meaning almost no (but not zero) heat transfer. And little chance of recovering the energy that is lost from the peltier effect.
http://jchemed.chem.wisc.edu/Journal/Issues/1996/Oct/abs940.html
Here is the thermoelectric series:NOTE how far away nickel is from the other typicals copper, silver, gold..
Now, from this link:
http://www.bartleby.com/65/th/thermoel.htmlThe text states:Joule heating.....I R squared...while peltier..rate of heat transfer proportional to current ONLY..NOTE: it is not dependent on the voltage across the junction, so does not obey joule heating, hence not a linear resistor.
http://www.xyroth-enterprises.co.uk/thermser.htm
OK after reading that stuff....here goes.
Take a copper terminal, and plate it with nickel..
If you run current into it, there will be heat flow across the metal interface as a direct result of the peltier effect. It will be small, so it will not produce a large heat flow..But, according to Peltier, it will exist.
There will be a small heat gradient across the junction. Because it's small, the carnot efficiency will be very small..
Now, drop that current...(like an audio signal does twice frequency rate)..
The already established heat gradient will now produce electricity, (well, at least according to Seebeck...but what does he know??))
And again, the carnot efficiency is low..so it will return the heat energy very poorly.
In the meantime, while the current is going to zero, the thermal conductivity of the metals on each side of the junction are trying to re-establish thermal equilibrium, by moving heat opposite to what the peltier effect did.
Now...Look at what just happened..the peltier effect took energy from the current and setup a temp gradient..the seebeck effect took some back, but both are low efficiency, and thermal conductivity prevented all the heat gradient energy from being returned to the system as electricity. (just like two buckets of water with a small pipe connecting each at the bottom. If you pump the water into one bucket from the other, you are putting energy into the system. with no leak, you can use the water levels to regenerate the energy (assuming a reversible, 100% eff. pump) but, the leak reduces your efficiency, and actually sets up a time constant, where high speed back and forth regains the most energy back, while slow back and forth loses more.)
The discussion of thermal diffusivity involves the rate at which heat moves in a metal..high conductivity makes it faster, high heat capacity slows it down..Aluminum has high diffusivity because of it's low heat capacity.
For junctions with metals, the high diffusivity is quite bad for efficiency, the heat causes a thermal short circuit..that is one reason thermoelectric heaters use semiconductors, to reduce the thermal conduction between sides.
Nowhere have I said that there is a DC/thermal gradient effect going on..I have continued to state that the metal to metal junctions will be non-linear in their I/V curve..IE..not a linear resistor.
""If we can establish a hypothetical link between the Seeback/Peltier effects and what we are seeing on a spectrum analyzer, THEN it's worth pursuing this further and testing it. If not, what's the point of this discussion?""peter
I have known of one for a while now...
""so perhaps there is an opportunity for thermoelectric effects. You just haven't described any yet.""peter
I have done so three times here...perhaps this time sucessfully?
Cheers, John
we're jumping posts again....you said:
Now, drop that current...(like an audio signal does twice frequency rate).. The already established heat gradient will now produce electricity, (well, at least according to Seebeck...but what does he know??))
Are you sure that's correct? I suspect the two effects exist in parallel at the same instant, rather than in a circular fashion.
When you "drop the current" and reverse it, you immediately begin to reverse the heat flow that happened previously, with a net of zero.
Also, the heat gradient has to result in a temperature gradient for Seebeck to apply. Given the high conductivity of these metals, the temperature gradient must be very small, since dQ/dt = -kdT/dx, right?
So, at 30mV signals into a 600ohm load, we have a current of 50uA. Signal freq = 5kHz, so one half cycle = 100uS
Total heating on one half cycle = integral of (diff in Peltier coeffs) x 50uA peak current over 100uS interval.
Temperature gradient dT/dx can now be determined from the heat flow (dQ/dt) and the materials' thermal conductivity.
Given that the thermopower coefficients of metals are down around 10 -5 to 10 -6 V/K, and we're depending on the heating caused by less than 10 -9 AmpSeconds of signal....
Don't have enough data in front of me to complete the math, but these are looking like very, very small numbers......
Peter
During the rise of the signal, the conversion is Peltier effect, setting up the thermal gradient..in a non linear current related fashion..After the peak, when the signal is dropping, energy will return as a result of the Seebeck equation. But, not at 100%, due to all the equation crap..(got tired of the verbage).
Then, the other half cycle does the same, albeit the heat flow and voltage swap polarity.
Then toss in the other confounding influence garbage...heat capacity, conductivity, plating integrity....major headache..
Hell, it's easier soldering a thousand joints than it would be figuring it out..
You said difference in peltier coefficients...The peltier efficiency will be a function of slew rate..I've no idea how to generalize or integrate the time dependent efficiency to develop a simple coefficient.
""Don't have enough data in front of me to complete the math, but these are looking like very, very small numbers......""peterIndeed, they are. But so is 120 db below 30mV.
""I suspect the two effects exist in parallel at the same instant,""peter
Yes, they do..but for peltier, the highest efficiency occurs when the sides are the same temp, or the reverse temp, while the seebeck efficiency is the absolute worst when there is almost no gradient. So they don't exactly balance out.
What strikes me the most is the current dependence for heatflow, and not current times voltage of joule heating..
Now, to really open your eyes, Peter...
All along, I asked for technical discussion about the POSSIBILITY OF THIS EFFECT HAVING SIGNIFICANCE for the measured results of JC's..
I did not state that it is what is causing it...I asked if it was possible...to that I got "bull shit".
You are engaging in the technical aspects, which is a pleasant change from what JC did. Thank you ..you are at least willing to entertain those aspects without glibly dissing me..
Cheers, John
Comments:I'm not tracking with your assertion on the other thread that the effect goes away as the amplitude goes up. Shouldn't this result in a greater assymmetrical heating effect during each half cycle, and therefore increased non-linearity?
OK, back to the calcs (check these and tell me if I screwed up):
120dB below 30mV is 3x10 -8 V, so we're looking for a number in that ballpark.
In JC's test, the heat current peaks at (diff in Peltier coeffs) x 50uA, right? I can't find the Peltier coeffs, but they are related to the Seebeck coef by Seebeck = Peltier/T, so at 300K the Peltier coeffs should range from 3x10 -3 to 3 x 10 -4 . If you assume worst case diff is 3x10 -3 , then the heat current is
1.5x10 -7 Watts. Probably much lower....If the junction is 1mm square, the area is 10 -6 m 2 .
So, we have:
1.5x10 -7 Watts = 400W/mK x 10 -6 m 2 x (temp gradient)
(using 400 W/mK for the approximate thermal conducivity of CU and Ag at 300K)So, temp gradient is 1.5/4 x 10 -3 = 3.75 x 10 -4 K/m.
I'm stopping here for now...
If you estimated the thicknees of the boundary over which this gradient occurs, that would give you a temp diff, which you can use to calc the Seebeck effect.
I still think we will come in way below JC's numbers, but I'm not ruling it out just yet...
Peter
I'm at home, no data here..You said Cu at 400w/mk. there's gotta be a length in there somewhere..Cu is 10.2 watts/inch-degree C. (sorry about the units, they say memory is the second thing to go)
Assuming the effect is real...It gets kinda tuff calculating it, because the diffusivity of the materials comes into play..as the gradient formed at audio frequencies is heavily dependent on the speed at which generated heat flows, both away from and towards the junction..so I can't readily calculate the zone or boundaries over which the heat can spread..
I'm not sure I can calculate with any accuracy the total effect, if I include Seebeck, Peltier, Carnot, and Joule..
""I'm not tracking with your assertion on the other thread that the effect goes away as the amplitude goes up. Shouldn't this result in a greater assymmetrical heating effect during each half cycle, and therefore increased non-linearity?""peter..
I'm not sure..that's why I asked my initial question..
But, consider the effect conversion efficiency..When the hot to cold difference is greater, the peltier efficiency goes down..So, for higher amplitudes, less conversion occurs. Yes, for Seebeck, it goes up with difference, but for the lengths of material on either side of the junction being discussed, thermal conductivity plays the great dissipator role.
That modulation of Peltier efficiency will happen at audio rates very near the junction (remember I Wag'd about 10 to 100 microinches??).
Those distances are verifiable for silicon, just look at the transient thetaJc stuff in the IR hexfet books...
Hmmmm..consider this...Assume a junction...Then, instantly apply lots of current....
Immediately, the peltier efficiency is some value (nano time frame).
As heat is absorbed(gradient forming), the peltier efficiency starts to go down.
As the structure continues to settle in, the peltier eff. still goes down..
Eventually, the eff. will stabilize at some structurally related number..But, before that happens, it is dominated by diffusivity of the materials. Before it stabilizes, it is horribly non linear..
But the efficiency is actually tracking in some fashion the slew rate of the current...which is the derivative of the voltage.
So, the dissipative loss is a function of the current slew rate, and that is quite non linear..
If we can really calculate the possible peltier/seebeck losses, we have to compare them to the joule losses of the IC..and those are definitely low..30mV/10Kohm/milliohms....
I wonder if the thermoelectric conversion losses are really that low compared to the resistive losses of an IC..in series with the load resistance of 10K..
You said Cu at 400w/mk. there's gotta be a length in there somewhere..Cu is 10.2 watts/inch-degree C. (sorry about the units, they say memory is the second thing to go)I found a couple of references to this number:
4 Watts per cm per degree C, which agrees with your 10.2 watts per inch per degree. Converting to MKS should give 400W per meter per Kelvin, unless I got the conversion the wrong way round and it's 0.04 W per meter per K....
Let me think this through....
The equation is actually something like:
dQ/dt (watts) = -k dT/dx (degrees/meter)
(the whole assumes unit area, BTW...)since dT/dx is degrees/distance, I think k has to be watts per degree per distance to be dimensionally correct....
Example: a 1 degree per centimeter gradient = a 100 degree per meter gradient, so....
I GOT IT THE WRONG WAY ROUND.... the thermal conductivity if Cu is 0.04W/m/K. Damn! So what effect does that have.....
The right calc is:
1.5x10 -7 Watts = 0.04W/mK x 10 -6 m2 x (temp gradient)
(using 0.04W/mK for the approximate thermal conducivity of CU and Ag at 300K)So, temp gradient is 1.5/4 x 10 = 3.75K/m .
Ok, now I need to go think about your Seebeck effect theory here...
Maybe tomorrow!
Peter
Again, havin fun with the subject line....When you said 400 w/mK, I thought you meant millikelvin...sorry..the guys here use millikelvin numbers in the dewars..ya had me major confused..that and a martini..
Ya gotta admit...it is interesting, isn't it??
Tomorrow, I gotta figure out how an optical encoder at 216,000 counts per revolution is losing 7.5 counts per turn..the magnetic analysis guy is roasting me cause of some harmonics on a serpentine quad I made using a computer thingy.....
I'm running out of things to test to find the drift error..pissin me off..big time..It must be the mechanical engineer's fault..it's always their fault...:-)
Peter, it's been a pleasure..later..
Cheers, John
Well folks, I didn't get an answer to my question. I got 'doubletalk' instead. What I want to know is how higher order harmonics can be generated by different cables of the same length and with similar RCA connectors, yet some others don't have much harmonic distortion. This effect diminishes at higher input levels. Also, I can 'corrupt' the my best cables somewhat, if I have 'dirty' connectors, so I clean them and all the associated components with industrial grade isopropyl alcohol, and other cleaners when I suspect any problem.
""Well folks, I didn't get an answer to my question. I got 'doubletalk' instead""JCI think I understand you now John..Your definition of "doubletalk" is any technical information you have not provided.
How many times will it be necessary to say it?????
THE SEEBECK/PELTIER EFFECT RESULTS IN A NON LINEAR I/V TRANSFER FUNCTION!!!!!!!!
Hellooooooo...are you there John??????
Non linear means that the voltage across the junction is not a linear function of the applied current..
Will it be necessary to explain how a pair of antiparallel diodes can affect a signal???? they have non linear I/V charachteristics..
Oh, maybe you didn't understand what I/V characteristic meant...if so, my apologies...It means that, when viewed on a curve tracer set to AC mode, the line produced is not a straight one, but shows the actual transfer characteristic.. I figured you knew what I/V meant...and it ain't for replacing body fluids.
Let's say, for the sake of the argument that Peltier effects can cause distortion like I am measuring. Well, why do some cables have it, and other cables not have it? Could it be that some cables are more 'distortion free' than others? That is what I am measuring. Of course, there is the matter of Dr. Van den Hul, who measured this effect, first, about 20 years ago. He couldn't know something about it, could he? So many questions, so many circles to go around. ;-)
""Let's say, for the sake of the argument that Peltier effects can cause distortion like I am measuring. Well, why do some cables have it, and other cables not have it?""JCHmmm...as I've said, it would be because of metal junctions in the current path. Plating junctions, connector junctions, dirty contact junctions(remember, your the one who said cleaning can affect it).
""Could it be that some cables are more 'distortion free' than others? That is what I am measuring.""JC
We wouldn't be having this discussion at all if I had simply discounted the possibility that some cables are more distortion free, as so many others have done...I am basing my discussion of Peltier/Seebeck effects on the possibility that what you are reporting is indeed happening.
You simply dissed me, attacked me and my motives, because you have gotten used to people attacking you and your results just because you are you, with your garbage attitude.
I came into the game late, so I don't know all the history of you..I do know that you have blindly sunk into a pattern of "if anybody questions you, then it is a personal attack", so you always see "commies" wherever you turn.
I choose to question the technical merits of what you are reporting..If you wish to discuss them, fine..I like that. If not, it's not my problem to deal with.
""Of course, there is the matter of Dr. Van den Hul, who measured this effect, first, about 20 years ago. He couldn't know something about it, could he?""JC
I wouldn't know...I've never heard the name "Van den Hul" in scientific circles, unlike Seebeck and Peltier....who is he? Has what he claimed to have measured been supported by other rigorous testing?? And, does he have a vested interest in the outcome of the tests??
And the worst question of all...did he use the same equipment you are now using? As I told Peter..it's useless to duplicate the exact same test using the exact same equipment using the exact same methodology if one takes into consideration the possibility that it is because of the equipment that the effect is being seen.
Why do some cables have it??? If you recall, I asked you if you had correlated the cable construction and materials and shield resistance with the results you obtained.. It was then that you attacked..so, to answer your question? I don't know, as I don't know what the cables you tested are made of..
It would appear you are getting close to actually discussing the technical stuff..I hope that is real.
Cheers, John
Of course, it could be a matter of junctions, but it could be internal junctions in the cable as well. Why not? Dr Van den Hul measured even more distortion than me, so far as I remember, and he measured at even a lower level with even quieter equipment. Of course, he only has a Ph.D in physics, what could he know or understand?
""Of course, it could be a matter of junctions, but it could be internal junctions in the cable as well.""JCI cannot discount the possibilities..that's why the models, the assumptions, the tests, the discussion..
""Dr Van den Hul measured even more distortion than me, so far as I remember, and he measured at even a lower level with even quieter equipment. Of course, he only has a Ph.D in physics, what could he know or understand?""JC
Hmmmmm....Didn't Fleishmann And Pons have Phd's?????? And what of Poletnikov with his PhD???. Who is the guy selling shares in free energy, he has a PhD also, doesn't he??? Oh yah, he's still avoiding federal fraud charges...runnin like hell, if I remember correctly..
Far as I know, cold fusion is still a pipe dream...as is gravity shields...Where did those PhD's get these people??? How many people get snowed by the fact of a PhD????
Yes, in most cases, a PhD does indeed show an elevated level of education, knowledge, and understanding...But it certainly doesn't guarantee it.. There are predators out there who will use a PhD to baffle others...that's why I asked...Does Van der Wall (sorry, van den hul) have a vested interest in the results he provided?? Is it possible that he is selling something that is decidedly better because of a test he performed and reported on, one which has never been duplicated???
I can't answer that question, as I've never heard of the man..so I can't speak of his legitimacy..
Course, he is not the director of a college program that has a faculty of two grad students and two visiting professors. Now THAT would be impressive..
Fleishman and Pons are still working scientists. Or didn't you know that? Ok, let's see it's now: Dr Hawksford, Dr. Van den Hul, Jon Risch, and me. Anyone else? Anyone see a pattern here?
""Fleishman and Pons are still working scientists""JCAh, yes...but would you buy a used car from them...especially if they claimed it got 54 million miles to the gallon (of water?).
Imagine the response from the rest of the scientific community if they said "gee, now we really have cold fusion...trust us"
How many centuries do you think it would take before another paper they write on cold fusion would even get looked at, nevermind published??
John...you forgot Politnekov...he claims that he has discovered antigravity. Something called a politnekov gravity shield..a spinning disk of superconducting material that seems to reduce the weight of any object suspended above the spinning disk by two percent..Of course, in the five or ten years since he claimed it, scientists from around the world have been unable to produce even a hint of the effect he said he measured..So, who do we believe...All the other scientists from around the world, with their millions of dollars of re-testing the setup politnekov published(NASA included, with 1.5 million)....or politnekov??? Why don't you invest some money in the scheme, John???Surely you trust he has discovered antigravity??
How much money do you have invested in cold fusion there John???
What about free energy John...That guy had a PhD...Did you get in on the ground floor???
""Anyone see a pattern here""JC
They should, John...
The pattern is: it is not very smart to believe everything that is told to you by someone who is, or claims to be a scientist, physicist, engineer, designer, doctor, professor, lawyer, used car salesman, (name the profession there John) without so much as a questioning glance???
More of the pattern: anyone who claims that e/m field theory is as they say in an article printed for a select readership, with the intent of that article clearly stated within (let's play for the gallery), when half the theory and premises and conclusions are incorrectly pulled from various subsections of e/m theory...should be looked on with reservation...as some of the worlds smartest e/m field theorists laugh at the mis-steps. I notice you have never answered any of the questions I posed of the article..of course, you can't, can you..
And even more of the pattern: Anyone who claims that they have 30 years of experience, so their word is gospel....regardless of the foolishness of their attitude, or the ridiculous dismissal of nobel prize winning theory....should be considered suspect. The fact that you swerve the dialogue to "you're being mean to me" every time it gets too technical is not lost to all here.
And more: When someone claims to have measured an effect, then makes money selling you something that avoids that effect, and yet nobody in the entire friggen world has been able to either duplicate or scientifically support their claims....they should be considered suspect.
Let's talk pattern here John...
Every time, without exception, that I have raised a technical point or discussion of a technical nature with you, you run and hide, yelling over your back "Boo hoo, you are being mean to me, to hawksford, to van de hull, to Jon," That's the third time you've invoked that in this thread alone..
Be a grownup, John..Either discuss the technical issues, or state the obvious fact that you don't understand them. Cmon, now, John..You can do it...everybody sees what's going on here..
It's not a crime to not know there, John..Everybody does it at one time or another..
At least Peter is engaging the technical side of what I talk about..I'm not sure if he is correct that the energy levels are significant for what I've been saying, but he's not running away like you are.. He may prove me wrong..and that's OK. But he's certainly discussing it, which is what I was hoping for.
You...You seem to be a waste of a moniker..I have remained open to the possibility that what people tell me about you is simply slanted and biased...but you do nothing to prove them wrong.
Hope you re-discover the technical side of the world, John. It would be nice to see you not turn tail and hide when technical details show up.
Cheers, John
What, does he own a cable company? Or write articles? Who is he?Should I just accept with blind faith whatever it is he said he measured? How? what did he measure??
If he has discovered some kind of micro-diode-current-thingy, that's incredible!
Why is it none of the big equipment manufacturers like HP, Tektronix, IBM ever mention the effect in any of their nanovolt and picovolt measurement equipment, you know, the 10 digit accuracy stuff that can damn near measure you farting in another county.. They've had twenty years to incorporate those findings in the most advanced measurement equipment in the world..
Perhaps you should give them a call? Tell them about your 30 years as a designer..Then they'll believe you. I know I would..
Cheers, John
you seem to have a definite opinion about John Curl. My opinion about you is that you are behaving abominably.I find your attitude offensive. You are talking out of both sides of your mouth, trying to have it both ways. On the one hand you are saying that Van den Hul should be written off because the effect he found was never found by "big equipment manufacturers like HP, Tektronix, IBM" blah, blah, blah. And yet you expect us to believe a bunch of *your* techno-babble about Seebeck and Peltier, which I'm willing to bet was also never found by "big equipment manufacturers like HP, Tektronix, IBM".
I think you are a big blowhard trying to impress people with your "knowledge" about the world of superconductors at (I guess) Brookhaven. Well, in my book there is a big difference between your theory and Van den Hul's. His has been corroborated by thousands of customers and dozens of reviewers. Your is apparently some off-the-cuff nonsense with no backing whatsoever, of any type. Who cares about that? Not me.
Furthermore, your attacks on Van den Hul are ridiculous. The fact that he sells cables does in no way nullify his findings. That is akin to saying Edison's theory of the phonograph should be discarded because he sold them. If by some miracle it turns out that you have stumbled onto something valid with your thermo-electric effects, you *should* sell a cable based on those theories. More power to you. In the meantime, I find your "theory" to be a big yawn.
""I think you are a big blowhard trying to impress people with your "knowledge" about the world of superconductors""CHI reviewed the entire thread...and can't seem to find anything about superconductors...what are you talking about??
I make no apologies for where I work or what my experience is, nor my knowledge..
And still state "for the record", none of those facts should be considered as reasons to blindly believe any hypothesis I propose. I continue to request dialogue and challenges to what I've proposed..
I do not consider "bullshit" to be an adequate challenge at a technical or intellectual level. Nor deflection of the discussion towards bashing me.
Note of course, I didn't deny the "blowhard" description..:-) And I'm not big (yet), but those big mac's ain't helpin. Nor the Denali Moose tracks.
""On the one hand you are saying that Van den Hul should be written off because the effect he found was never found by "big equipment manufacturers like HP, Tektronix, IBM" blah, blah, blah.""CHNo, no, no.. I have asked why it is the big manufacturers have not used, nor concerned themselves with an effect that was found by VdH 20 years ago. On which should be affecting the measurement technology on the leading edge..
""And yet you expect us to believe a bunch of *your* techno-babble about Seebeck and Peltier, which I'm willing to bet was also never found by "big equipment manufacturers like HP, Tektronix, IBM".""CHActually, the King of Sweden gave medals to some guys for finding the effect I speak of..
And, the effect I speak of is in constant use by Omega instruments in their entire product line. You should peruse their catalogs (boy, have they got some) to see the extremes they go to in order to maintain accuracy of their product against bot peltier and seebeck.
And why are you deflecting the issue here? running interference?? As I've stated quite a few times here, I have only proposed the effects as a possible solution to the measurements being reported.
So, if your gonna post your opinion, tell the truth instead. The truth being (go ahead, review the posts):
I am proposing a strange combination of known effects to explain the distortion being measured...
I am discussing levels of possible effect with Peter.
I have stated Peter might find me incorrect, which I state again, is OK.
Peter at the moment feels the effect may be at the levels necessary, and I have questioned that feeling (even though it's supporting my hypothesis.)
And, I have said outright, the statements and theories of all supposed guru's, salesmen, scientists, engineers (included because I'm one) must be questioned, and gave some classic examples of higher level guys who, even thought they had Phd's, were wrong.
You, in your "buddy buddy" post, have neglected to mention the fact that I have invited technical discussion of my hypothesis. Hello!! I'm inviting criticism and discussion of my hypothesis!!! Are you there? Can you read this? That would appear to be an entirely new concept to you as well.
""Well, in my book there is a big difference between your theory and Van den Hul's.""CH
I totally agree..My theory is being tossed up here with the intent of discussing it, modifying it, learning it, it's level of interaction, if any. That includes tossing it out if it indeed fails to explain what it is being used for.
Curl, and apparently you also, are revering VdH's theory, placing it abov reproach.. While, at the same time, you come up with this gem:
""His has been corroborated by thousands of customers and dozens of reviewers.""CH
I note with interest that you did not say that the theory has been corroborated by anybody with a high level of technical background. So who has duplicated his result? You failed to provide that information..
""Your is apparently some off-the-cuff nonsense with no backing whatsoever, of any type""CH
That is the way all good theories start. And all bad theories..Course, peltier and seebeck theory is adequate backing, don't you think?
The difference you are missing is the step in the middle, where the theory is hashed out, re-worked, used to provide predictions, and then tests devised to confirm or deny those prediction.
That is how science progresses Charles..not the bellicose "Phd, 30 years, nonsense..
I've no ties to my hypothesis..it's either right or wrong. but I toss it up for all to discuss. That's the way it works.. Not some "pay no attention to the man behind that curtain".
""Furthermore, your attacks on Van den Hul are ridiculous. The fact that he sells cables does in no way nullify his findings""CH
AHA. So he sells cables, and has a vested interest in maintaining an edge over others, which he does so with his theory and results.
Where have you been, Charles??? As I posted to Jon Risch with respect to blue jeans cables and their tests..Yes, they indeed have a vested interest in the outcome of their tests, but that does not necessary nullify the validity of their results..AND I stated that Jon WAS ABSOLUTELY CORRECT in that the vested interests are to be concerned with.
So Charles, you call pointing out a conflict of interest w/r to VdH an attack here, while you allow the exact same thing Jon Risch stated about blue jeans cable to go right on by?? Talk about selective vision.
""That is akin to saying Edison's theory of the phonograph should be discarded because he sold them.""CH
Geeze, Charles....not only did he have a theory, he clearly demonstrated it and sold it..
Why not use a far more fitting example here Charles?? Try free energy. It's being hawked, sold, and yet it has never been duplicated by anybody anywhere..Like the gravity shield..But, investors are buying into it..
""If by some miracle it turns out that you have stumbled onto something valid with your thermo-electric effects, you *should* sell a cable based on those theories""CH
Hmmmm. not interested. And, quite impossible to patent, as posting it in the public domain makes that impossible..
So, I do not, and cannot have a vested interest in this theory of mine..I've only posted it as a possible mechanism for distortion.
""In the meantime, I find your "theory" to be a big yawn.""CH
You are also entitled to your opinion..
I find your unimaginative attempt at distorting the entire history of the thread to be a yawn..But, it was fun reading fiction..
You are also welcome to participate in a technical discussion of the theory if you wish..as is everbody. Even Curl, the one I first proposed the theory to, hoping for a technical discussion..
Cheers, John
PS.."you seem to have a definite opinion about John Curl""CH
No, I have an opinion about the content of his posts..I do not know him, nor will I accept the rather low opinions of him others have provided me..My opinion of him will be formed on his behaviour towards me.
""My opinion about you is that you are behaving abominably""CH
Again, your opinion...but you really should review all the posts before you glibly toss garbage up here.
My example of cold fusion and free energy and gravity shields was introduced solely to show that a title, or an education, or experience in some instances, does not make what is said gospel.It was provided with the intent of stating that all results, theories, hypothesis, pronouncements, should be questioned.
Not discarded, but questioned..
So do not erroneously assume that it was mentioned to categorize VdH's results as fraud or nonsense...but to question all..
That is how I view skin theory, grain boundary collisions, micro-diodes...that is also how I view my own hypotheses..with a questioning eye..
As to Edison...bad example..He provided a product, that of converting acoustic waves into physical modulation on a storage media..easily seen..easily tested, easily done in different ways, like flat disks. His technique fell into disfavor because each cylinder had to be recorded one at a time, and he had a hand in deciding what was to be recorded. At least the disks could be stamped. (imagine singing a tune a million times?)
VdH has measurements that have never been duplicated by the big boys, and after 20 years..never even considered as viable or valid..
I've not stated he is a fraud or charlatan..just that the big boys don't seem to even see the necessity.
It is possible his test was confounded by something the big boys have addressed, I wouldn't know..But, I would certainly question..
As for my theory being a big yawn? Most of this techno crap is a big yawn to the vast majority of the population. That's the downfall to being a geek..
which suggests that the net effect should be zero for AC current. The junction is heated on one half-cycle, and cooled on the other.However, you're saying that the transfer function is changed during each half cycle, which is a cause of non-linear behavior.
In that case, shouldn't the non-linear component increase with increasing signal amplitude? As the current increases, the total heat increases before reversing (the difference in the Peltier coefficients times the current integrated over the half cycle)
According to John, the effects he's seeing disappear at higher amplitudes, more akin to a crossover distortion effect.
Not really, just wanted to lighten it up a bit, that last post to you gave me a headache..Read my post to you above, then this one.
""which suggests that the net effect should be zero for AC current. The junction is heated on one half-cycle, and cooled on the other.""peter.
Because of the delta T, the carnot efficiency will be low..and it's Seebeck effect for the opposite way..
I think the most important thing is that because the carnot efficiency is so low, there will be energy lost to the conductor, which will not return..
And because the energy conversion goes as current, the transfer occurs in a non linear fashion..It's that non linear part that got me thinking about the applicability to JC's results.
""However, you're saying that the transfer function is changed during each half cycle, which is a cause of non-linear behavior.""peterYes, I'm saying that it is a combination of Seebeck, peltier, and thermal conductivity coupled with finite heatflow speed away from the junction that gives the non linear behaviour.
""In that case, shouldn't the non-linear component increase with increasing signal amplitude? As the current increases, the total heat increases before reversing (the difference in the Peltier coefficients times the current integrated over the half cycle)""peter
Peltier and seebeck coefficients with carnot efficiency..
And don't forget, the levels of energy loss we are talking about are actually small, as is the joule heating loss..But, as the levels increase, the joule loss increases faster than the peltier/seebeck effect, so the effect gets smaller as the drive goes up..
""According to John, the effects he's seeing disappear at higher amplitudes, more akin to a crossover distortion effect.""peter
I know..that's why I've given so much thought to thermoelectric type effects and how they would have to fit into what is observed. It would be silly for me to try to fit it otherwise..
I visualize the problem as a pair of antiparallel diodes in series with a 1 Kohm resistor..at milliamp levels, the diode dominates (say, half a volt plus 1 millivolt of resistor drop)..but at one ampere, the diodes disappear (actually, about one volt out of one thousand)
It's good to actually discuss the technicals for a change. Thanks
Cheers, John
Since the HP 331 doesn't have a built-in oscillator, I've been using my old signal generator. According to the HP, it has about 0.04% distortion. I had wondered about filtering it. Seems like a simple passive bandpass could work. I haven't done the calcs yet to figure out component values, but I might get a chance to do that this weekend.The spectrum analyzer should arrive on Wednesday, so I will be able to see what the distortion actually looks like in another week or so.
You might be better off with an adjustable filter. If I remember correctly, and this goes back quite a few years, Krohn-Hite used to make something for this purpose.
That's the direction Im thinking about. Either bandpass or lowpass filtering the oscillator output to get rid of the harmonic crap
I consistently find it amazing that you defend the undefensible, and then have the nerve to insult those who question the obviously flawed.
I'm curious as to why you don't use steel wire in your interconnects like you apparently do inside your products. It seems like the strength of the steel conductors would be much more important in a cable that is exposed to a fair degree of handling, compared to zero handling for cable inside the product.
If you had any reasonable command of theory as opposed to high end marketing I would bother to respond to your ridiculous post.
I have missed it, and you're correct about the reason, too. While I wouldn't pin blame on any particular party for the bickering I've seen, I generally opt not to read Prop Head threads once any bickering starts - I find it too difficult to extract useful information from those threads.I'm not doubting that John has found some useful measurements, but I do have to question whether those measurements are widely accepted or not. It would seem the answer is no. If these are indeed valid measurements for detecting small differences, how do we convince the skeptics of this?
-Pete
PS - If my assumptions about the acceptance of existing measurements are wrong, please do point me in a direction where I could learn more about them if possible.
Let's get real here. We need 'better' measurements than what is conventionally assumed to be adequate. I tend to work in that direction, but you will not get Dan, Steve, or Jneutron to get off their duffs and do so. It is easier for them to nit-pick or whitewash over the whole thing. They won't either try it themselves or accept my efforts, so we are at a stalemate. It will never change, as long as SE is on this website.
One must always determine the accuracy of the equipment used when doing a measurement..That accuracy includes the entire setup, with all it's foibles and limitations.
John....from your posts to date, that is not something you subscribe to.
Tell me John..did you ever make a real high bandwidth load resistor, or are you still using the caddocks?
Instead of detailing your efforts at characterizing your equipment, you constantly complain about other's questions.
Your attitude is not conducive to imformation exchange, as the closer people get to seeing your setup errors, the more you clam up..and inform us of your 30, 40, 50 years experience..
I welcome you providing some technical input...as I've said, I'm a patient man..
I detailed at great length how to calculate the thermal resistance of a semiconductor die all the way to the heat sink..that is what this site is all about.. technical exchange, not your bellicose barrage of bravado..
John:It seems to me this is a bit one-sided.
Could you please describe the test set up YOU use to make measurements on AUDIO equipment?
I know you work on a lot of very exotic projects at work, but I'm curious how much of that transfers over to actual hands-on work with audio gear. If you get to use the facilities of the national lab for making audio measurements, then you're a very lucky guy. Perhaps you would like to duplicate John's set up, and report on your results?
It's easy:
Set up low distortion oscillator feeding a distortion analyzer via the DUT. Use analyzer to null out the fundamental. Take output of analyzer and view on a spectrum analyzer. Look at harmonics of fundamental. Simple.
Since you could clearly set this up with a lot more care than JC, given your far greater expertise, this should be child's play for you.
I am also setting up a similar environment to examine the same thing. Which one of us will have some real results first?
Peter
In trying to find out what John is doing, I was brushed off..There is some equip here I could glom, but don't know if it's any better or worse than what JC has. No info has been forthcoming from JC to determine the relative merit of the equip I have access to.
I want to characterize the equipment for the task, but wanted to know how JC did such for his setup, only to find he didn't.
I resigned myself to designing up an IA setup, using the CMMR of the device to null out the drive and cable signals, but find that the resistors TCR makes the circuit very sensitive to thermal variations on the order of bout half a degree. So, started work on a thermally controlled plate in an insulated package, with the intent of keeping temp variations down to about a tenth of a degree or better. (at work, they typically measure to within a millikelvin)
And, I am also wrestling with the fact that the cable under test forms a ground loop, and how to keep the shield resistance differences from altering the response of the setup..Then summer hit, and I hit the road for a show here called wiz bang. 'Taining about 1000 people every sunday, this sunday the last of the year.. Then I can get back to play..
So, although it seems that just pluggin the stuff in should work, there are quite a few gotcha's that will throw the measurement off, and some of those gotcha's will be cable specific and repeatable, while actually artifacts of something that is not being accounted for..
""Which one of us will have some real results first?""peter
You, my guess...I'm gutting a kitchen to put up s'rock, cabinets, and tile floor..leaving about 30 minutes at lunchtime every day for play, when I'm not jogging or swimming.
""Since you could clearly set this up with a lot more care than JC, given your far greater expertise, this should be child's play for you.""peterThe detail required for this measurement is not child's play. And my "expertise" is in getting smacked in the face with the fine detail things not accounted for. Hence my desire to actually understand the test equipment and it's weaknesses. and to explain those weaknesses to all.
Cheers, John
My idea of using the IA CMMR seems to get around the worry of the distortion of the oscillator, and the distortion of the nulling circuit, while concentrating on amplifying the difference between what goes into the cable and what comes out. I'm not sure if it will work as I think it will, but had posted the idea before here, with no criticism of the technique from anyone, so I still stab in the dark here.Near as I figure, if my osc had 1% distortion, that 1% would be nulled out at the IA by it's CMMR to say 120-130 db down (assuming I can tame the resistors down), leaving the cable error to be amplified. This vs trying to get the osc to have distortion 120 db down, or a really tight null.
I'll actually use an HP 3325A for source, but don't have it's specs available as I type.
It's a pity that you (like all of us) have a life other than audio (well, maybe not all of us....) ;-)If you can create a new measurement system that gives us a better way to look at cable signatures, then that is real advancement.
Good luck with it.
I also like the IA approach because I also want to use it to difference the signals at either end of a speaker wire run into my 18 pole resistive load. Kill two birds, so to speak.
nt
I believe this post should be over at Music Lame (sic), or some-such... ;^ )
Wow, love that answer! Sorry to see anyone blaming anyone else for disagreeing with them, but the "good riddance" type post is ludicrous. As I see it Prop Plaza is failing because everyone is pretty fond of pointing out how little is supposed to be known about sound reproduction and how everything remains a mystery wrapped in an enigma. Why is it that no engineer or designer from the very large concerns that have the financial wherewithal to actually come out with significant advancements such as CD, SACD, DVD, multi-channel or whatever are never heard from?
CD was *not* an advancement! ...Except insofar as noted in the article liked below. It was a marketing ploy, to get people to buy a whole new record collection, sound be damned.And if one of those Sony/Phillips guys could explain why tweaking a CD produces superior results, I for one would be *very surprised*. I don't think they really understand digital audio.
clark
For those of us who are too young to have ever bought more than a few silly records, the CD freed us from the cassette tape. We need to keep in mind that not too many people ever listened to vinyl in their cars or on easily portable systems. In that context, I think the CD is a pretty damn good solution. Sure, it could have been much better for the audiophile, but us loons are a small part of the market and difficult customers to boot.Regardless of the countless techincal sonic issues with CDs, it is a much more convenient medium than anything else available in the mid-80's, and we all know the mass market loves convenience.
Of course, you're probably multiple decades older than I, so I wouldn't expect us to have the same context on an issue like this :-) If I had any sort of meaningful vinyl collection when CDs emerged, I would probably think/feel differently, too.
As for your wish, if I remember correctly, I believe a Sony rep did chime in on one of the threads regarding CD track sequencing versus jumping. The gentleman stated that he had heard the effects of this phenomenon, and that his rig was immune to it due to the numerous pieces of expensive gear in his digital front end. I don't recall his name and can't find the post for the life of me though, so I may be nuts.
CDs are certainly an improvement over cassette.The only problem from an audiophile perspective is that it lowered the absolute maximum attainable sound quality.
It acted sort of like a compressor; it brought the lowest fidelity systems up to a pretty high level (witness what's now possible in a car), but it also lowered the top end slightly.
It's taken until very recently to get CD playback up to the level of vinyl.
I abandoned vinyl (mostly) in favor of CD, and my 750 records say unplayed for the last 10 years. A month ago, I invested in a reasonably high end table, and I am completely blown away by (or maybe just reminded of) the musicality of vinyl.
Just a reminder Clark; this is 2003 not 1983. The CD has exposed more flaws in recording techniques than most people care to imagine. However, people like you are essentially dysfunctional because you are so accustomed to the high noise and distortion of 78's , tape, and poorly designed tube gear, that you really have lost any grip on what live unamplified acoustic music is really all about.
Many of the recent recordings I've heard are compressed to death; the only goal seems to be to get the level as high as possible. This (unfortunately) also seems to be the norm for concert PA management -- crank everything up until it's simply a wall of distortion with zero dynamic range.With a few exceptions, it seems like we're going backwards, not forwards...
I wonder if the convenience/portability/durability of CD has contributed to this? For example, lots of people (including me) play CDs in their cars, where you have to use compression or you lose music down in the noise.
BTW, in the CD-is-good-or-evil debate, there's one thing that is rarely talked about:
The CD was pushed to market with whatever sample rate was possible given the silicon available at the time, not the sample rate that was determined to be appropriate for good sound. Given the Moore's Law rate of chip improvement, a 12-24 month delay in the release of CD might have given us a far better medium with less sonic compromise.
Anyone who looks you in the eye and claims that a brickwall filter at 20kHz and a 16-bit sample rate is "perfect sound" is deluding themselves. Anyone looked at the distortion spectrum of a CD player at -40dB (where a lot of the music is) instead of at 0dB?
Notice that Sony is now touting the audibe benefits of SACDs extended bandwidth? But wait, we can't hear anything above 20kHz.........
Stop listening to pop music which tends to be deliberately done in this fashion. Listen to some TELARC classical discs and then tell us what you hear. You may want to check out this article I wrote for Audioholics.com which may help you understand what's going in in the studio.
http://www.audioholics.com/techtips/specsformats/CurrentFormatTrends.php
I just wish it was a bigger percentage....We've got two different directions happening:
The people who care are making better and better recordings; those who don't are getting worse and worse.
a
""But wait, we can't hear anything above 20kHz.........""peterProve it....
Human hearing directionality response is capable of 20 microsecond ear to ear delay, with some actually able to discern to 10 uSec.
That is the realm of 1 foot side movement of a source ten feet away. So it is my expectation that 44Khz sampling rate is unable to duplicate soundstage with total accuracy.
The timing resolution of a 44.1kHz system is greater that the sample rate ie 22us.
Agreed. But the transient information within the recording can only be in 22 uS time steps.On a sample by sample basis, that could blur the soundstage, a transient could be very close to the sampling time, and on occasion show up in the stream one sample later.
HowdyNope, if you for a moment assume that there is no level quantization, an appropriately bandlimited transient can show up in any phase and be correctly reconstructed. E.g. the sampled point isn't necessarily the peak, the correct peak will be there after the reconstruction filter.
I wasn't talking peak level.What I was getting at, is that an analog transient that crosses zero (arbitrary point of course) at any instant can show up in the sampled datastream up to 22 usec later. In fact, any analog transient superimposed on a slower signal can have the temporal relation shifted between the two waveforms by a max of 22 uS..
HowdyFine: it's also true that with the same assumptions a zero crossing can have any phase after the appropriate reconstruction filter. The phase isn't quantized by the sampling rate. The sampling rate affect the highest representable frequency.
Think about it, with no quantization of level, any appropriately bandlimited signal can be reproduced accurately. Putting it more simply, any sine wave with a freq less than the Nyquist rate can be easily represented and reconstructed and only if it's freq is rationally related to the sampling rate will there not be all possible phases of zero crossings present.
The real fun starts when you start quantizing the levels and/or you try to time limit the signal.
Ted:When you say
an appropriately bandlimited transient can show up in any phase and be correctly reconstructed. E.g. the sampled point isn't necessarily the peak, the correct peak will be there after the reconstruction filter
You're right, but doesn't "appropriately band limited" mean containing no signals with a component at more than half the sample rate?
So a 44.1kHz stream can't contain any anything above 22.05kHz, i.e nothing with a period of less than 45uS.
If there is information in the original signal that the ear/brain can discriminate down to the 20uS range, does bandlimiting (and therefore the subsequent A/D/A) have the effect of eliminating/smoothing/smearing that information?
HowdyMy whole point is that the sample rate isn't in and of it's self responsible for quantizing phase. As I point out in my response to John, with no quantization of level, all phases are possible. When you quantize the level things are more interesting and the sample does come into the picture, but it's been many years since I took DSP courses and my books are packed so I won't even try to come up with the relationship of quantization of level to resultant phase effects.
Perhaps Werner or some one else who does this stuff actively for a living will chime in.
you're right that anything up to half the sample frequency will be perfectly reconstructed (assuming no jitter, of course....)Now how does that jive with the fact that we can apparently hear arrival time differences down to around 20uS, or half a sample period? Doesn't sound like a CD has that level of time resolution.
I know I'm mixing up a bunch of concepts here, which is why I'm having trouble connecting the dots....
Peter
HowdySince you can represent any given sine with an arbitrary phase, you just add enough up to give you the attack or transient you want with what ever phase you want. (Limited by Nyquist for highest freq and ultimately the level quantization introducing enough errors which smear the time resolution.)
CDs can represent left and right channel phase differences which are quite small, smaller than a sample period. This is probably how great CD players with low jitter get a precise soundstage, even for higher freq instruments like the triangle, etc. (I'm just hand waving here.)
I don't know the exact time resolution of Redbook, but the simplistic argument that it's one sample period is clearly hooey.
""If there is information in the original signal that the ear/brain can discriminate down to the 20uS range, does bandlimiting (and therefore the subsequent A/D/A) have the effect of eliminating/smoothing/smearing that information?""peterMy take? absolutely.
In fact, take a look at a 44Khz sample rate of a 15 Khz sine wave..The reconstructed waveform looks like three 1 Khz sines superimposed in three phase..so the peaks are riding three crests..
The only way to get back to the real wave is to reconstruct with a wide window, whereas cd replay is point to point..Blowin Nyquist theory out the window..
Cheers, John
HowdyNope, if you use a proper reconstruction filter a 15k sine will be precisely a 15k sine after reconstruction.
CD is not point to point.
Look at the waveform..You will see what happens..I wish I could post a pic here.
HowdyI have. I used to write software for digital audio workstations.
Be careful what hardware and software you're using. Many software programs display samples connected by lines not what the waveform will look like when run thru the reconstruction filter.
that was fast..Yes, by looking at the dac immediately before any filtering, you see the step waveform. And the peak values at that point are visibly riding three sines. But, post filtering cannot reconstruct the peak value of the 15Khz signal on a cycle by cycle basis unless the filter is resonating at 15Khz.
Nyquist theory assumes the ability to reconstruct using more than one sample, much as an FFT requires many points.
It would be nice to have someone chime in who can support the math to show how point by point reconstruction is not really pure nyquist theory. I can't.
How do I get pics here?
HowdyHere, for example is a 14kHz tone (actually to keep your #'s correct I used a 14031.81818181Hz tone at 44.1kHz) displayed by a real program Cool Edit Pro.
HowdyPoint by point reconstruction introduces higher freqs than the Nyquist rate.
Anyway, we are off track. The whole point is that a proper filter allows finer time resolution than a naive 1/sample rate argument would indicate. An improper filter is more sloppy on the time resolution.
HowdyAs I said we are assuming band limited signals. If you are talking about only one cycle of a wave form that is decidedly not bandlimited.
Nyquist shows that as long as you have incrementally more than 2 samples per cycle of your wave you are OK unless you are extremely unlucky, e.g. you have a signal whose freq is exactly a rational relationship with the sample rate. Since the rational #'s are sparse in the real #'s this is rare :)
And if you are bandlimited you have many cycles of your signal so you see the correct peaks, etc.
If you have a picture host you just put the URL for your picture in the 'Optional Image URL' when you post. You can also put in the HTML IMG tag, if you want it somewhere other than at the top of your post. If you don't have an image host, the Asylum provides inmate picture galleries for contributors.
Thanks for the pic info Ted..""And if you are bandlimited you have many cycles of your signal so you see the correct peaks, etc.""ted
Agreed..but look at your 14 khz waveform...you really have to wait around to see the sample coincide with the actual peak of the waveform. You are making the connection in your thinking that when the two coincide, that is the actual wave amplitude..
Reconstruction of that signal by a DAC...For the dac to really output the correct amplitude of that signal, it has to look over many samples to get the right amplitude..Hence, my point..
Now, if you were to "connect the dots", so to speak, with some filtering, you should see some envelope modulation..what is interesting is that the top of that envelope is not symmetric with the bottom one, there will be a frequency component there. And, nyquist math does not produce that artifact, unless you include the FIR response of real filters, representing the very few samples that are actually available to the filter. Also, don't forget, Nyquist math requires sample lookahead in order to work..
Thanks Ted
John
HowdyHave you read all of my responses on this thread?
You don't have to wait for the peak. Look at the waveform that Cool Edit Pro displayed. The program had no idea what I gave it. Here's what I gave it:
#include#define _USE_MATH_DEFINES
#includeint main () {
const double sr = 44100;
const double sp = 1/sr;
FILE * h = fopen("out.pcm", "w");
for (double t = 0; t < 1; t += sp) {
double a = sin(t * (M_PI * 2) * (sr / (44000.0l/14000)));
short s = int(a * 32767);
fwrite(&s, 2, 1, h); }
fclose(h); }
Cool Edit Pro (and your DAC) have no idea what waveform I gave, but the peak is reconstructed accurately from the samples present.
Anyway go listen to your 14kHz sampled and reconstructed at 32k, 44.1k, 48k, 96k, etc. They all sound the same to my ears and have the same amplitude. It also agrees with theory. Why would I believe yours eyes instead of mine and my ears and the theory?
HowdyShould anyone want to play with this stuff to recreate my examples you might want this slightly corrected code. If you don't open the file in binary you'll get weird extra bytes now and then :)
#include#define _USE_MATH_DEFINES
#includeint main () {
const double sr = 44100;
const double sp = 1/sr;
FILE * h = fopen("out.pcm", "w+b");
for (double t = 0; t < 20; t += sp) {
double a = sin((2 * M_PI) * (t * 154350.0l/11));
short s = int(a * 32767);
fwrite(&s, 2, 1, h); }
fclose(h); }
""Cool Edit Pro (and your DAC) have no idea what waveform I gave, but the peak is reconstructed accurately from the samples present.""TEDTed...try presenting it the samples from .19625 to .19655 only.
Bet it doesn't give you the correct peak..
Looked at the notation you provided..fraid I'm clueless as to what it says..my fault, not yours..
What is the math cool edit pro uses to reconstruct the underlying waveform? is it the same math that is applied to the output of a CD??
At first, I had thought the oversampling techniques did that, but apparently not.
""Anyway go listen to your 14kHz sampled and reconstructed at 32k, 44.1k, 48k, 96k, etc. They all sound the same to my ears and have the same amplitude.""ted
The only thing I have to play it back on here is cd type stuff..so I can't yet do that..My newer 24/192k card may support that, but it's still in the box..I think I'll just build a new computer around it instead of the infernal problem of "new hardware found".
""It also agrees with theory.""ted
In theory, yes..but the application is not up to the theory. My DSP prof's never used truncated signals to support nyquist. They did, however, show how truncated signals cannot provide optimal reconstruction. Some kind of convolution between the sampling window and the signal of interest, from what I recall..definitely fuzzy on that, though.
""Why would I believe your eyes instead of mine and my ears and the theory? :)""ted
Ummmm because I'm such a nice guy???. :-)
A really cool test of what we speak? Take the pure file, .wav it, play it into a typical CD player, and scope it..Then use a parametric set high Q, look for the artifacts I see with my eyes..by scanning the parametric across the 500 hz to 5 k range.
You're correct..It's my eyes here, not my ears..And I also think I wouldn't hear a diff over the rates..
I love this crap....
Thanks Ted,
John
BTW, does 25 dollars get me the ability to put pics on AA? Cause I really like AR for that capability.
HowdyIf you give a DAC or the program too few samples you are convolving a rectangular window which by definition has infinite bandwidth.
The code I gave is C++ and it generated the .wav file I used as input to Cool Edit Pro and that I played out my DACs.
Cool Edit Pro is simulating a DAC by applying the correct brick wall filter and then resampling at the rate dictated by the number of pixels on the screen (or thereabouts) to draw the waveform.
Sorry I don't have to do your parametric filter test, I've been there, done that, etc. If I had my Digital Audio Workstation alive I would do the experiment just to humor you, but then you'd need to understand it's algo's to believe that it's doing the experiment you want. On the other hand I don't happen to have this kind of analog equipment laying around at my house to do the experiment in the analog domain. But like I said I used to do this stuff for a living and remember people arguing about this till the cows came home. I also have bad memories of people not getting it in school when they were only doing the math and clearing things up for them in another lab where I had the equipment to demo things for people. In a previous life I've written similar display code to that of Cool Edit Pro, just so customers didn't get confused.
Just because I thought you might ask, tho, I did play this file thru three of my DACs and got the same answer, no 1k envelope modulations (boy I'm glad my daughter wasn't here when I played that, she'd be complaining that I'm deaf at that freq.)
Yep, make a donation to the Asylum and get hosting for anywhere. Rod doesn't limit the pictures to just be displayed at this site.
Did you try the limited sample size on the program? When you do, please post the pic..I remain unconvinced...But I'm really enjoying the conversation..thanks Ted..
When I get the chance, I'll put together the analog stuff to prove it either right or wrong..but I fear my time budget makes for a large queue.
I don't know if it's 1k envelope mods, or some weird thing. But I'll certainly think about all you've said..
Donation? Cool, I'd love to post some pics..got my 100 foot linecord/mike/snake that doesn't hum..my 18 pole resistive high bandwidth coaxial load..and soon enough, my IA setup..along with the pc test setup.
HowdyHere's a selection:
Here's the display after pasting that selection into a new waveform:
You can see the window effects caused by assuming that the other samples are zero.
I know..that's what I've been talking about..The DAC does not have the information from the future, nor the past..The output filter will only have the past..
And note..how would a filter output a signal that is higher in amplitude than the sample? points 4.5 and 9 come to mind.
Ted...thanks for this cool discussion..going offline now, be back monday..gotta take the kidlets to see medallion..
HowdyOf course a reconstruction filter produce outputs higher than the input, otherwise how could they reproduce the original waveform without waiting for a peak :) A reconstruction filter isn't just a smoothing filter. Anyway ever hear of filters ringing? If you hit a reconstruction filter with a single non-zero sample, you'll not only get an output of some amplitude at that point but also non-zero outputs at other points, when there are more than one sample those other "spurious" outputs can overlap constructively or destructively and cause the output at any given point to be higher or lower than you might otherwise expect.
The reconstruction filter is a part of the DAC.
To do a proper brickwall filter it must look into the future a little, (by delaying the output a little) but that has it's own problems...
There is no such thing as an ideal implementation of a reconstruction filter, but in any case the better the filter, the better it's time resolution... which is what brought the whole thing up in the first place.
is the idea that you can completely create a sine wave at or near the Nyquist freq with only a couple of points.I think the key concept is that the data points allow only one waveform to be reconstructed that does not have components above the Nyquist freq. In other words, in order to create any sharper curvature in the waveform, you would need higher freq components that cannot exist.
This also means, of course, that you don't need to have the peaks, or any other particular part of the waveform, sampled in order to recreate the band-limted wave (as you said before).
Boy, this is easier to understand than it is to explain.....
Howdy"Boy, this is easier to understand than it is to explain....."
You said a mouth full there. There is a reason some (well motivated) people drop out of signal processing theory classes :) And here on the internet you don't even have the advantage of knowing the audience and the audience having the requisite background.
Agree on mouthful and audience.To recover the peak signal, the reconstruction math has to work quite hard, and requires samples around the peak of interest.
There will be a tradeoff between the window size and the ability to reconstruct the waveform beyond the simple DAC hold between samples.
I make the assumption that most CD outs are simple filtering of the staircase DAC output signal after the hold circuit.
I do like the thought of a digital brickwall filter, as that could easily include a large sample delay for better implimentation and reconstruction. My thinking has been only on analog filtering.
I don't know what is right, because I don't do digital,but thanks for the info. Ted. I can learn something from this exchange.
You may well be right, but the 44.1kHz sampling rate issue pales in comparison to loudspeaker/room issues. Also note that most microphones roll off very quiclky above 20 kHz. The few that have extended frequency response are rarely used because the noise level is too high.
But, with two identical speakers, with their identical foibles (identical being relatively so), soundstage can get mucked up if the system delays some of the info in the 20 usec range.How do typical cd players run?..My soundcard, at that rate, alternates channels for A/D conversion. So there is a built in right to left time shift. My vinyl does that when my cartridge is not tangential to the groove.
You've got interleaved converters? If that's the case, my suggestion is to get something with uniform group delay. I think you'll appreciate it.
I don't know about my cd players or my denon 1800..Just my soundblaster platinum live..That's why the 24/192 card...
I have a The Phillips CD1 test Disc which has about 99 different tracks for CD test, including delay. Should I get you a copy? That and a scope will tell you what you need to know.
I'll be taking you up on that at a later date. thanks..
about the 20kHz limit. I think extended bandwidth is intuitively better, provided you don't start running into interference/EMI/ radio pickup issues. Less chance for causing unintended problems.I find it funny that the same company that claimed you didn't need to go past 20kHz (when they couldn't) now claims the benfits to going to 100kHz (because they can).
And yes, I also believe that steady state sine wave hearing tests don't tel you much about how we hear music.
nt
I really can't hear a direct tone much above 14Khz.
Which makes me think that how we "hear" above 20Khz is
by changes in image location and size and shape.Why else have two ears, if not to hear these subtle
timing differences?
I'm close to 17Khz.But, I'm really surprised by the ability to hear 20 microsecond timing delays, cause that implies that audio systems need to be phase accurate way over hearing BW to keep directional information intact, otherwise soundstage is compromised..but we actually don't hear the freq's up there..
""But, I'm really surprised by the ability to hear 20 microsecond timing delays, cause
that implies that audio systems need to be phase accurate way over hearing BW to
keep directional information intact, otherwise soundstage is compromised..but we
actually don't hear the freq's up there..""
What has time delay to do with freq's up there?Is it not to totally different things?
A 20 Khz sound has a period of 50 microseconds, for reference.Many systems are described by either the bandwidth, expressed as the frequency where the response is 3 db down, or by the risetime of the system, how fast it can respond to a change of signal. The relationship between the two is inverse, as in Freq is proportional to 1/slew rate.
A system which is capable of responding to a 5, or 10 uSec transient usually is a system that has a very high bandwidth, one which is far beyond human hearing capability.(I've been saying 20 uSec, but the study I saw had several subjects clearly distinguishing down to 10uSec.
To say that a human can distinguish a 10 uSec difference in delay almost implies that we can hear in the 50 to 100 Khz range, which is clearly not possible.
But to get 10uSec response from an audio device requires the designer make the amplifier capable of very high bandwidth response.
As John Curl said, he claimed he heard the diff between a 35 Khz filter and a 100Khz filter..But, he is not saying he can hear up there. My take is that he can hear the transient response differences, although some would try to take him to task as saying that he is hearing 35Khz stuff, which he did not say.
Take 3 kHz as referance.
Take two signals, and delay one 15 deg.
Take stereo, and a very good radiating speaker, one would have no problem telling the shift in location of the signal.The brain can tell what ear is first. What has that to do with very high bandwidth? That is what I do not understand. I do find it to be two totally different things.
is that the fact that we can localize sounds using delays in the 10-20uS range, which is less than the period of a 20kHz sine wave. In your example, both signals are arriving at both ears, separated by very small delays. How does the brain distinguish one signal from the other?The conventional 20kHz upper limit of hearing is based on tests using (I believe) steady state tones.
Doesn't this imply that the notion that we don't need info > 20kHz because we can't hear sine waves over that frequency may be a gross oversimplification?
So, you are right that there is not a CLEAR connection between these two things, but one does seem to contradict the other.
It is a gross simplification that because we cannot hear over 20Khz, that 10 uSec information is useless..Calculate the difference in time between right and left ear for a source ten feet away, and one foot off axis..that seems like a reasonable thing for a species that used to depend on hunting to survive..Course, it also is a reasonable thing for the existance of a soundstage between two speakers 10 feet apart, and ten feet away from the listener.
Mtry on AR (or was it Radar) gave me some links to the studies that showed the human subject response to L-R delays...Some subjects ran down to 10 uSec capability, statistically valid..And yes, it certainly does seem to contradict..
So I certainly wonder how a 22 uSec sampling period can be capable of conveying 10 uSec information necessary for soundstage.
Your example of 3K, 15 degrees..1/3k is .33 milliseconds per cycle, 330 microsec's.
15 degrees is 15/360, or .041 of 330, 13 uSec...good example...
For a stereo amp to reproduce that with R-L coherency..yes, it doesn't need 100 Khz capabilities..in fact, 3 Khz would do, as long as the channels match..
But, for an amp to faithfully follow a complex audio signal without introducing transient delays at that speed? Hmmm..each channel has to faithfully reproduce the audio signal, without affecting the time relationships between, regardless of the signal content..I do not know how to design an amp that is low bw. but still faithfully passes 10 uSec transients..
To answer your question...some believe it is necessary to have high bandwidth in order to maintain the time relationship between the lower frequency information and the higher freq stuff. I think I belong to that group. :-)
I am absolutely confident that I have not answered your question to your satisfaction...I'll think about it...Sorry...
NT.
It removes the tension between the "tests have shown you can't hear > 20kHZ" crowd and the anecdotal reoprts that extended bandwidth matters.I think there is way too little attention paid to the time-domain behavior of audio systems, and the impact on sound quality.
As Dan B. would certainly point out ;-), the time domain errors of most speakers are much worse than those of the upstream electronics.
However, if you could look at the cumulative time delay errors of the entire chain from microphone to speaker terminals, I bet it would look pretty horrific. I suspect that 44.1kHz A/D and D/A makes that even worse.
Peter
Peter, I would like to inject in here, that in 1974, Jon Meyer and I had our really good research lab. We used B&K 4133 condenser mikes that had an extended response to 40 KHz or so, and a pretty good pulse response, better than 9us risetime. This is better than most microphones then or now, BUT Mark Levinson, Stellavox, The Grateful Dead, and others used these mikes as their working reference. We found that they sounded 'more extended' DUH ! ;-) They were quiet enough, thanks to me, because I lowered their noise by about 10dB in the electronics.
Better than this is difficult, but it sure beats CD's, even perfect ones. We found that our hearing is not completely limited to what people say: Many people, especially when young, can hear extended respose to about 25KHz, but what seems to be really important is 'transient response' . I have run 'informal' tests myself where we could easily tell the difference between a 35KHz single pole filter and an 100KHz single pole rolloff. Tough nuts to those who have never tried it, properly.
""but what seems to be really important is 'transient response' . I have run 'informal' tests myself where we could easily tell the difference between a 35KHz single pole filter and an 100KHz single pole rolloff""JCAnd that is of course, consistent with the oversampling crowd with their use of higher breakpoint filters.
The only writeups I've seen so far on the oversampling didn't actually say we could hear way up there, but they also didn't mention any transient response things that are bonafide proven, like the ability to hear 20 uSec L-R delay changes. Perhaps they should..
20usec is 50Khz.In order to accurately preserve timing info,
does that mean 10x... so 500Khz?
I wonder what the entire audio chain looks like viewed from this perspective?pretty ugly...
I don't think I can emphasize the difficult part enough. I can't blame big buck manufacturers for not wating to take a beating here, much as I'd like to learn from their input....
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I mean, *of course* there are differences!
even a fairly casual DBT.Surely some people must have better ideas.....
I like my idea....:)page 9 of this manual diagrams it.
That seems like a good test for amplifiers and preamps (I didn't yet look at the reaction to your post to see what others thought of it).I'm not sure that the method could be applied to sources and cables, however, but it certainly wouldn't be the first time I was wrong about something.
I think that amp design represents some real progress in the measurement arena, though. I especially like that it puts some power in the hands of the consumer and only involves a mild amount of tinkering.
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