Once upon a time, decades ago, a number of circuit designers researched what it takes to make a proper RIAA EQ, without overloading, either it amplitude or frequency.
Shure Brothers published a paper in the 1960's or 70's that gives the amplitude of virtually every record ever made. The frequency sweep was measured by me, in my 'Omitted Factors for Audio Design' for the IEEE in 1978. If you need a copy, I will try to send it to you.
Shure Brothers published a paper in the 1960's or 70's that gives the amplitude of virtually every record ever made. The frequency sweep was measured by me, in my 'Omitted Factors for Audio Design' for the IEEE in 1978. If you need a copy, I will try to send it to you.
Hi Jürgen, nice to have you around.
PB2 : yes, the time segment is shorter, that was a typo. I try to get a paper or some other information from Test Factory about that test. I called ones but they did not call back and then i was too bussy. Sorry for letting you in the shade. I will try to collect some information tomorrow. My opinion on the Null test is that a speaker should be connected and the test should be made at very high volume with very dynamic material.
To make that test, you whould need a soundproove chamber or you can really hurt your ears. I do not know if tests like that have been made. Usually the level is much lower on null tests. I do not think that an exotic distortion mechanism will show up but the interplay between amp and spaeker is not fully researched. Dr. Klippel works on that probem since 30 years and i see in his software updates that he is still refining his model. There is a lot of hysteresis and energy storage going on that is extremely hard to model. One provocative statement : maybe a technical perfect amp does not sound as good to the ear because recordings, rooms and speakers are not perfect but we are working on it.
By the way, i saw your website. You have been involved into some serious high tech.
I am genuinly impressed that a man like you got interested in what i am doing here as a hobby.
One last thing. I had a somewhat strange idea for a DC coupled FET Low Z MPP.
PB2 : yes, the time segment is shorter, that was a typo. I try to get a paper or some other information from Test Factory about that test. I called ones but they did not call back and then i was too bussy. Sorry for letting you in the shade. I will try to collect some information tomorrow. My opinion on the Null test is that a speaker should be connected and the test should be made at very high volume with very dynamic material.
To make that test, you whould need a soundproove chamber or you can really hurt your ears. I do not know if tests like that have been made. Usually the level is much lower on null tests. I do not think that an exotic distortion mechanism will show up but the interplay between amp and spaeker is not fully researched. Dr. Klippel works on that probem since 30 years and i see in his software updates that he is still refining his model. There is a lot of hysteresis and energy storage going on that is extremely hard to model. One provocative statement : maybe a technical perfect amp does not sound as good to the ear because recordings, rooms and speakers are not perfect but we are working on it.
By the way, i saw your website. You have been involved into some serious high tech.
I am genuinly impressed that a man like you got interested in what i am doing here as a hobby.
One last thing. I had a somewhat strange idea for a DC coupled FET Low Z MPP.
Sure, I'd like to have a copy if it's not too much trouble. I'll PM you my email address.
It seems to me that the null test can be used to prove/disprove many theories. If the claim is that we do not have a measurement instrument to measure some new form of distortion - we know that a null test will reveal all types of distortion. If it is that a more complex test signal is required - it will work with nearly all test signals or even music. If the claim is that it is a speaker interface issue then yes as you note it can be hooked up as in the Hafler test.
I really don't see the amplifier speaker interface as any sort of a mystery. As I'm sure you know the mechanical parameters can be "pulled" through to the electrical side and then simply appear as a reactive load to the amp - it is nothing more than a reactive load. Energy storage? All reactive components store energy. Yes, the non-linearities are complex, however iron core inductors also have complex non-linearities. We have to keep in mind that we are driving a motor and from that perspective it is fairly similar to rotational motors.
By the way, have you looked much at the XBL motor drivers?
My passion is audio, it is what sparked my interest in electronics as a very young boy starting with tubes. My emphasis in college was analog and RF design, but then got pushed into digital at my first job. Most mysterious issues with high speed digital implementations are analog and transmission line related so all of my past interests applied.
I like projects that can be built in an evening or a weekend and it is refreshing to use parts out of our junk bins for prototyping. I would much rather design or build a simple circuit than do a crossword puzzle, lol! Low noise design is also challenging so I have found your thread interesting - thanks for sharing your work.
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When i can trust the work done at Meridian and also Würzburg University the ear can be compared to a 21.5 Bit 96kHz sampling digital system at least in the upper midrange where it matters most. That kind of performance from source to ear is not awailable right now. So null tests should be done with that resolution at least. How that can practically be done escapes my vision. The null you see on the screen may not be a null in reality.
Actually a null whould be not posible on the quantum level because it creates a singularity.
I learned in University when i studied Telecomunicatione that the ear actually is so sensitive in certain parts of the spectrum that it is even exepting some noise from air molecules hitting the tymphany. When you go to sleep late at night in a rural place you still hear some noise from that effect. Peope in remote aereas of Norway call it "Roaring Silence".
There are a lot of well edjucated engineers on this forum that have perfectly sound arguments but i never heard a sytem so far that resembles the life experinece of unamplified music. That is also the reason i beleave that a perfect amplifier has not been build yet whatever your test equipment will tell you. A perfect amplifier whould be something with inteligence build in to compensate for flaws in the chain. DSP is only childs play at the moment but i like the idea to know the flaws of the reproduction chain. If we whould know that flaw and whould be able to work to very close tolerances, a "perfect" amp could compensate it. But that is a totally different system theory. Just adding "perfect" elements just does not work because the ear-brain is not a microphone.
Actually a null whould be not posible on the quantum level because it creates a singularity.
I learned in University when i studied Telecomunicatione that the ear actually is so sensitive in certain parts of the spectrum that it is even exepting some noise from air molecules hitting the tymphany. When you go to sleep late at night in a rural place you still hear some noise from that effect. Peope in remote aereas of Norway call it "Roaring Silence".
There are a lot of well edjucated engineers on this forum that have perfectly sound arguments but i never heard a sytem so far that resembles the life experinece of unamplified music. That is also the reason i beleave that a perfect amplifier has not been build yet whatever your test equipment will tell you. A perfect amplifier whould be something with inteligence build in to compensate for flaws in the chain. DSP is only childs play at the moment but i like the idea to know the flaws of the reproduction chain. If we whould know that flaw and whould be able to work to very close tolerances, a "perfect" amp could compensate it. But that is a totally different system theory. Just adding "perfect" elements just does not work because the ear-brain is not a microphone.
This is not true a repeated measurment with the same stimulus will have the same output + noise each time which will yield to averaging. Think about it, please.
Reference please? The sound of your own nervous system and circulation is far above the Brownian noise limit.
"John Cage found that he had heard two sounds while in the chamber,
one was a high-pitched sound and the other a low-pitched sound. The engineer
he was working with informed him that the high sound was his nervous system,
and the low sound was his blood circulation."
I am just testing this :
http://www.analog.com/static/imported-files/data_sheets/ADA4898-1_4898-2.pdf
it has a very low 1/F corner frequency but there seen to be issues with the feedback resistor.
The AD797 is the best low noise chip i know so far. In the right circuit it is hard to measure distortion, belcher test and noise modulation included.
http://www.analog.com/static/imported-files/data_sheets/ADA4898-1_4898-2.pdf
it has a very low 1/F corner frequency but there seen to be issues with the feedback resistor.
The AD797 is the best low noise chip i know so far. In the right circuit it is hard to measure distortion, belcher test and noise modulation included.
That refers to single frequency threshold. I have been 30mi from everything in the northern woods myself (@-30F) and in an anechoic chamber and I still feel the circulatory system accounted for all the low frequency "rushing' noise. Here is an interesting reference but I'm not about to spend $31.50 to satisfy curiosity.
The influence of stochastic behavior on the human threshold of hearing
References and further reading may be available for this article. To view references and further reading you must purchase this article.
Ilse Christine Gebeshubera, b, ,
aTU-BioMed, University of Technology, Wiedner Hauptstr. 8-10/1145, A-1040 Vienna, Austria
bPhysics Department, University of California, Santa Barbara, CA 93106, USA
Ok, i will go more deep into it and will be better prepared to answer.
What researchers at Würzburg told me is that the ear sensitivity goes up by 40dB if a short
high frequency pulse hits the ears so there is some diferentiation of the input signal going on. They measured the nerve firing rate with high frequency pulse input. To avoid impulse disturbance from the loudspeaker they used Manger Transducers (MSW) in a kind of big headphone arangement.
Tomorrow i will call Daniela Manger for more information.
This thread get´s hard work !
What researchers at Würzburg told me is that the ear sensitivity goes up by 40dB if a short
high frequency pulse hits the ears so there is some diferentiation of the input signal going on. They measured the nerve firing rate with high frequency pulse input. To avoid impulse disturbance from the loudspeaker they used Manger Transducers (MSW) in a kind of big headphone arangement.
Tomorrow i will call Daniela Manger for more information.
This thread get´s hard work !
I live in deeper countryside and often hear the passage of blood in/around my ears; most often in the early morning should I wake from sleep unexpectedly. It is not the same as that deepest silence of truly remote locations in still-air conditions when the silence is deafening. At times I also fish in very remote areas and am now well used to the experience! [It can also create unexpected emotional response.]
My own experience is that when either sound or vision reception has no external reference of any sort that one becomes disorientated. Walk deep into a photographers infinity vision chamber - I've forgotten the proper name - and one's whole sense of physical balance and even existence appears threatened. Having seen six sheep being photographed in the total whiteness of this chamber - which is an inverted half oblate spheroid with a totally matt-white finish... it was obvious that they were very distressed indeed by the altered visual context. [They had refused to enter and had to be carried in. Once on their feet again they refused to move and had to be manually placed in position.]
If an object is placed at the correct point in this chamber it visually appears to float. The lighting is such that no shadows are thrown, and there is simply no line or point of visual reference. I have also been in an anechoic chamber, and I imagine that if all visual stimulus were also removed one would would go quite mad in a short period of time!
The point of these observations is that they show, me at least, that a real time reference is a requirement for any form of normal visual or sound experience to be valid.
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We used to walk about 1/2 a mi into the storm drain system to get total sensory deprivation. I understand the feeling. I still think the brain is reacting to the confusion and it is not simply the "noise floor". Ikoflexer sent me a link to that paper on how stocastic resonance figures into this. This is clearly beyond a casual discussion of anecdotal experiences.
