Multi-stage and very low cutoff freq. well below any signal which is releted to music......
Drift in dc output is usually very slow and thus so should the dc servo. 0.5 Hz or less is good. There is No bleed thru of a 'signal' at drift freq. And if well buffered, no HF bleed thru either.
Besides doing the drift correction by applying dc correction at the same point as audio feedback is the most popular way but I have seen better and less sensitive places to control dc drift in output offset. Especially in the newer CFA designs.
We should look at those carefully, as well.
DC offset at the OPS should be minimized by reasonable matching of the transistors and then after warm-up set by trimmer to zero. After that the dc servo controls any drift in dc offset.
THx-RNMarsh
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I know for fact that isn't true. Provide proof, the old twenty questions sessions that went round and round don't count. I think the folks here have enough respect and deserve that. I don't mean an odd mistake or oversight either.
As for experts this is no different than the continued linking to the Bateman articles or the picking capacitor articles neither of which saw peer review.
There is certainly a dearth of expertise here. Anyone seriously trying to advance the art on this would take more care in experimental setup. Using windowed magnitude only FFT's throws out valuable phase information. Using harmonically related tones to try and measure both THD and IMD makes no sense.
Harmonically unrelated test tones synchronized with the FFT clock so a single bin holds both magnitude and phase information is trivial to instrument. Some here understand this stuff.
So is that your test setup generator, R/C, measuring instrument? I'll gladly repeat the measurements (I think I have some Vishay S102 resistors somewhere). , not that you would pay any attention.
I want deescalation of the personal affronts, and more civil discourse instead.
I was speaking in the context of responding to someone else, and I way trying to say what might be needed to convince one particular person while at the same time trying to be careful not to escalate anger and personal attacks.
To be clear regarding my position on capacitors: I remain unconvinced that high quality capacitors always cause audible problems if in a signal path and should never be used. That opinion is subject to change in the future should I be presented with good evidence to do so.
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Hum. Whatever the point where you return the DC feedback, you will modify the current's balance between a pair of symmetrical transistors. If this DC correction is applied right where is the unbalance that produced the DC offset, you will reduce distortion. If it is in an other point, you will add a second unbalance, then, increase distortion.
Matching transistors and minimizing DC offset in absence of the servo, then applying the servo in the audio feedback point don't look so bad, don't you think ? Even if applying the servo output voltage to modify current sources, as an example, can seem further from the signal/feedback path. In fact, where is the difference ?
Sure. Understood, in theory. Like the idea, but haven't gone though a process of figuring out how to implement it, given what equipment I have available.
Sure would be nice if someone who has done it using a plain old sound card would write it up so that the technique can be more readily available to all who would like to use it.
EDIT: Like many other things, what is "trivial" depends. There are some things that might be trivial to others that might take some thinking on your part if it's out of what you normally do every day, or you haven't done something of that exact nature for some time. This is true even for the smartest and most accomplished people I know.
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Not so much misunderstanding but most probably more like ignorance. It is very common for people 'in audio' having no clue on how they hear, how they perceive sound. Many have the naive view that what moves your eardrum, that is what you hear.
If you are really interested in these issues and study the body of knowledge, it becomes very quickly clear that what you 'hear', i.e. what comes to the forefront of your consciousnesses as what you hear, is only partly based on what moves your eardrums. Expectation, experience, the shape, color, price, prestige of the item you listen to, the situation with your friends, how you feel at that moment, all determine to some extend the total of your sound perception. That is also why your ears are totally unreliable as to what is audible, except in carefully controlled tests. That is also why in carefully controlled tests, where you are thrown back on your ears only, many previously experienced differences disappear.
IF you are really interested in these things, please do yourself a favor and read the attached. It is a section from a larger study, which I have but is too large to attach. BLIND vs. SIGHTED TESTS – SEEING IS BELIEVING. - you owe it to yourself to educate yourself about what interests you.
Jan
May-i ask-you the same question ?
When we design, measurements, simulations, etc... helps to improve the performance of the work in progress. But it can be as useful as increasing the speed of a car when everywhere it will be used the speed will be limited at half this value.
This permanent arrogance !!!!
This certainty of holding the absolute knowledge and truth...
To know how to listen, in a conversation as in the matter of audio, it has to be learned.
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That's why looking at a second order passive lowpass on the output of a servo is a good thing. Belt and suspenders. Of course that gets us back to using caps in the system.
Apropos nothing of what I quoted above, it's important to note that a 1uf coupled into the input impedance of an AP (100 k impedance? How flat over bandwidth?) is a different test to a 3.3 uf capacitor coupled to the parallel impedance of 10k and the input impedance of the AP. Long and short, the knee of that filter should be about 1.6 and 5.3 Hz respectively. Also, Sy's sweeps are across the audio bandwidth versus solely focusing on where a 5.3 Hz filter is actually somewhat active.
And, man, am I not the only one who found SY's writing style humorous? Have we sucked all the fun out of language with nannying?
Hi Mark,
I know SY personally.
So while SY is fair and open minded, he won't consider a change in point of view that depends on conjecture or lack of experimentation if he has already proved something to be a certain way. He also does not suffer fools who are very vocal and do not provide anything that can be considered as solid evidence.
In person, and on the web, SY is very articulate with a great sense of humor (that can be dry at times). His sense of fairness and right and wrong does put him at odds with anyone trying to fleece the public selling or recommending anything that attempts to claim special characteristics or benefits that either can't be proved, or have been proved to be false. This will put in conflict with people around here that we know push those kinds of products. Bybee comes to mind instantly as a good example of this. I share this trait with SY.
To suggest SY is anything but straight forward and honest demonstrates that that person doesn't know SY, and that they are probably engaged in selling or recommending products that claim something that is counter to the evidence that testing for those claims has shown. SY's integrity is what keeps him employed at jobs that sometimes do require testing to prove an idea or concept. He can't afford to be anything less than completely honest.
-Chris
I know SY personally.
Actually, he is extremely fair and objective when it comes to these issues. Agree or not, SY follows the clues and test results. He is extremely good at setting up experiments and will always report the truth. If you could figure out a test that is reproducible to support your point of view, SY would recreate your test and honestly report even if it was at odds with his previously held beliefs. But that is only if your experiment controls all variables except the parameter in question (otherwise the experiment is flawed and a waste of time).
So while SY is fair and open minded, he won't consider a change in point of view that depends on conjecture or lack of experimentation if he has already proved something to be a certain way. He also does not suffer fools who are very vocal and do not provide anything that can be considered as solid evidence.
In person, and on the web, SY is very articulate with a great sense of humor (that can be dry at times). His sense of fairness and right and wrong does put him at odds with anyone trying to fleece the public selling or recommending anything that attempts to claim special characteristics or benefits that either can't be proved, or have been proved to be false. This will put in conflict with people around here that we know push those kinds of products. Bybee comes to mind instantly as a good example of this. I share this trait with SY.
To suggest SY is anything but straight forward and honest demonstrates that that person doesn't know SY, and that they are probably engaged in selling or recommending products that claim something that is counter to the evidence that testing for those claims has shown. SY's integrity is what keeps him employed at jobs that sometimes do require testing to prove an idea or concept. He can't afford to be anything less than completely honest.
-Chris
Wait a minute, please. It seems like Jan is maybe half right or more. Just not completely. There is a lot of truth to what he says, but its not the whole truth.
You know. There are audiphiles who buy expensive wood cable lifters and other stuff that is hard justify, either by measurement or by use of learned listening skills.
Where Jan has thrown out the baby with the bathwater is by appearing to be overconfident that all he knows is all that exists.
Jan: There are skilled listeners which maybe you have never personally encountered. They have not to my knowledge ever been properly tested. Earl Geddes has said that existing hearing research probably applies to about 95% of the population. He said new tests would have to be developed to test the other 5%. So, you are right that some hearing abilities have never been proven, but please don't say it in a way that leaves a reading impression you are sure it can never be proven.
EDIT: A couple of posts by Anthony Bisset in another thread explain some things about listening skills rather nicely, I think.
http://www.diyaudio.com/forums/digi...le-difference-whatsoever-154.html#post5336603
http://www.diyaudio.com/forums/digi...le-difference-whatsoever-159.html#post5342324
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Hi Chris,
I don't know Sy, I have only read his words here in the forum and in his articles.
With regard to Sy, he may be a fair and unbiased when in an experiment, but to say that he does not suffer fools, is to say that he is very biased when not experimenting. Most people are not fools and don't deserve to be treated like bad people, and not everybody that disagrees with Sy is fool either.
Regarding what you said, I was going along with you pretty well until you said "and that they are probably engaged in selling or recommending products that claim something that is counter to the evidence that testing for those claims has shown." To be clear, I don't think Sy is always right, and he appears excessively and unjustifiably rude. In addition, I don't sell anything at all.
Mark, I agree that there are surely lots of things I don't know, also that all I know is not all that exists.
But let us start to learn to crawl, walk then run. If people would understand that hearing is NOT just what moves your eardrums, we can crawl. We can then move to more advanced topics like: how can I train myself to do better in attempting to take into account the fact that my brain draws in all kinds of things that have noting to do with the sounds, and still be able to report on the sound alone.
And this is hard to do: you are up against millenia of evolutionary selection, that shaped the operations of your brain in interpreting your senses. In the attachment I gave, it is said that his own trained listeners told Toole that they knew how to listen, they wouldn't be fooled, they knew the traps. Professional listeners. Yet they fell for it big time.
So Earl says he can. Well, as long as he remains human, I am very skeptic.
Jan
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Okay, thanks. That's one data point. As another data point, I am a self-trained listener and freely admit I can be fooled. But, I figured out how to tell if I am being fooled or not. I use my own system of blind testing that I find works, and it does so comfortably for me. Until I can reliably pass my blind test, I never come here and make a claim as to what I can hear. But, I sure don't use Foobar ABX for it. It's fine for easy to hear things, but too distracting for things that require deeply focused listening. Such listening might be likened to playing a musical instrument with good or more than good skill: It requires practice, focus, and a lack of distraction to do one's best.
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No. The opposite- they are connected to our brains, which are highly flawed and open to suggestion.
Yeah, that's back to the "but, but there's a CHANCE someone's out there that can". Of course we cannot prove a negative nor do we have a complete characterization of the human population (through all time and situations).
I'm reminded quickly of what a (senior) coworker of mine said at a meeting, "the likelihood that you've exactly picked all the wrong people is pretty slim, so we can't expect that a bigger study is suddenly going to show something new".
Also, I didn't read a lick of what Jan wrote as "knowing the whole truth", but "this is a better picture of the landscape as we know it". So, be careful not to snap judgement (we're all guilty, right?) about some sort of intonation.
I gladly change my mind and admit to mistakes when I make them (I have made some real boners). John posted my findings on DA from a long time ago and I have changed nothing about my opinions.
The classic R/C ladder model of DA includes no non-linearity the fact that there can be some non-linearity in some capacitors also is besides the point. The statement was made that the DA model with ideal capacitors has some IM distortion mechanism hidden from conventional analysis. That is the differential equations with R and C as constants don't give the "right" answer.
Why can't folks simply say, "I was wrong on this", and move on. No one would think anything less of their contributions.
As for your second point, the issues are completely separate for me and I'm not that interested in what is audible to some unless it is backed up by more than the usual weak evidence. Ed mentions J.J. IME he would never publish findings that he stood behind professionally without rigorous DBT evidence that would stand up to peer review. From what I saw years ago on USENET he spent more time telling folks what they probably can't hear.
As for experiments there were the faster than light neutrinos as well as two famous challenges to relativity. They all fell to bad experimental practice one taking decades until better data reduction techniques were discovered. The criticisms all were aimed at the findings not the people, in fact they bent over backwards to respect the care in taking data of the original experimenters.
Look, I am trying to avoid coming straight out and saying it's more than a chance, it is quite real. I can do it blind myself and have many times. All of which is true.
Why not say it in that way? Because then people just shift their arguments to what I say isn't proven and I may be hallucinating and not know it. But, of course, Sy always performs his science perfectly!
Anyway, if by now you trust me to be honest and not self-deluded then you can believe me, or otherwise not. I don't want to talk and argue about me personally! That's not what this is about.
Maybe I can say it this way: There is more than a chance, IMHO. There is an almost certain probability that many people can sometimes hear more than they are currently given credit for based on prior hearing test protocol evidence, again, IMHO.
Now that I've said it straight out, I don't want to argue about it. I have given an opinion, that's all.
Well, you know the answer of Peter Walker about *hi end* cables: "I tend to prefer the ones that conduct electricity."
I had several conversations with Rupert Neve about the best methods to design. And we agreed on this: Listen, measure and listen.
As we have to learn how to run measurements, if we want them to be accurate, listening is something to be learned as well.
The first thing is to know what you are listening to. (Face of your wife in a crowd)
The second is to avoid situations where you have to listen back and forth to figure out a sonic difference: you will loose your time, get tired and open the door to deception, fooling yourself.
Having spend half of my professional life designing commercial audio electronic gears, both in consumer and professional areas, and the other half in producing records, I tend to consider I am not so unwashed as Jan seems to suppose I am.
And I can be a little upset, and feel insulted, when he write things like "Not so much misunderstanding but most probably more like ignorance".
The guy is often right, when he talk about electronic theory. But he seems to feel himself engaged in a war against "audiophiles", considering all those who use their ears as superstitious naïves, believing in snake oil.
I don't need to loose my time in measurements to figure out how grainy can be a electrolytic cap, used in the signal path, compared to a good (industrial) film one. As well as good metal film resistances compared to carbon ones. And no need hours neither to decide that any subtle difference between this film cap and an audiophile one at ten time the price, if any, is not worth the price.
This said, I could use "wood cable lifters" if you offer them to me and if they look good in my listening room... after all I buy chairs or tables for their beauty and can even sacrifice some comfort for the price of their beauty. ;-)
I will certainly not even try to listen to any difference with/without.
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And nobody will argue about an opinion, me included. Or I should say: nobody should argue about an opinion. It is personal and up to the, ehh, person. It may or may not have a relation to reality, but that is beside the point.
Jan
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