Its not a mater of belief, it's taking someone's work and claiming it is a technical proof of their theories. The particular connection between high open loop BW and distortion as stated is provably wrong, Bob Cordell has done it and so did that link I posted. If you build amps according to Otala's rules and subjectivly like them that is a different thing.
It was better than that, Wayne. I came to ye olde England in September 1967, and started my grammar school (high school) education there. At the time, the system required you to pass O (ordinary) level exams after two years, and then A (Advanced) levels after the other two years.
Your choice of subjects at both O and especially A levels determined your chances of enrolling at a university of your choice, as per the list of requirements each one of them had.
So, in 1969, I passed my own seven O levels, and much to the surprise of my English teacher, actually got a grade 3 in English language. Official O level diplomas carried no grade then, but the initial notice did have the marks. It turned out he was uncertain I'd even pass, and I not only passed, but got a very high grade (grade 6 was a pass, grade 1 was as rare as wisdom teeth), and my British friends scraped by with grade 5 being the best.
Next, I enrolled for the A level courses, did the first year, but went back home to Yugoslavia in July 1970, as my dad's tour with UNESCO was over. This turned out to be most fortunate for many reasons, but that's a long and very convoluted story up Alfred Hitchkok's alley.
Then dad went on to complete his work for the UN in Cairo, Egypt, leaving me to study at home and visit every three months or so. So, just for a change, I was allowed to actually complete my university studies in one, straigh run, with no funnies in between. Sometimes, it's just great doing things the plain vanilla way.
Americans. You Americans are actually resposnible for teaching me just how relative things can be, and often are. When dad first started working for the UN, his first post was Ankara, Turkey, where he taught meachine elements, probably the hardest part of being a mechanical engineer. Mom and I joined him in February 1964. At the time, my "knowledge" of English boiled down to reciting "Twinkle, twinkle, little star" - literally. At home, we had just started learning foreign languages at school.
Then I found out that we lived in a part of Ankara which was almost all inhabited by US Air Force personnel and their families. Remember, in 1964, the Cold War was on full force. Ankara alone had an Air Force and Army population of over 30,000. So, who did I have to play with, at a tender age of 11? Americans, that's who.
Thank God I was blessed with an ear for languages, because I went from zero to hero in 3 months flat. From nothing to fluent (at that age). Half of that was sheer inborn talent, the other half hard work. I won't bore you with details, but trust me on this, February-July 1964 was the hardest part of my life, get up at 6 AM, work, work, work all day, go to bet at 10 PM, free time Saturday afternoon. I did it all, and rather well at that. But I wouldn't wish that on any child.
Believe me, you cannot even imagine the cultural gap between those kids and me. Enormous! But still doable. Without actually realizing it, or being able to vocalize it, I learnt that there is a world of difference between a country's policy and actual people behavior. Like Air Force mothers serving us kids afternoon sandwiches without bothering to even ask who's who. I was just another kid on the block, who just happened not to be US made. I even got stitches, courtesy of Uncle Sam and the Air Force, at their hospital, after my head happened to be in trajectory of a rock; Dave, the guy who threw the rock, had a very unpleanst close encounter with his dad's service belt right there, on the street. I reckon he got off worse than I did, but we still stayed friends.
As for your comment on education capabilities, don't write the US off so quickly. In 1991, I helped a professor from Babson College near Boston organize a seminar for young enterpreneurs. This resulted in a month's worth of a seminar, mostly in Boston, but also in NYC. Walk down their alumini lane and you will see some far from insignificant faces hanging on the walls, for example, people like Ken Olson (who invented Vax and established Digital as a company), Charles Wang, and so forth. True, that is very much a rich man's school, but quality is NOT an issue. Some of their concepts were, though, but hey, what's the academia to do but argue concepts?
Yep , I know about "O" and "A" levels
... I took my O Levels in 77 ......
Interesting take on the vinyl stuff , I'm of the same disposition , I have no problems with digital either , but I do hear what analog does so well. As for selling Hi-Fi, you have to be a member in that club , nothing to do with product, they will make it the best after acceptance ..
Head Phones Needed
Celestina Boninsegna - TOSCA (1908) - Truesound Transfers - YouTube
You will hear the impossible . If you don't understand you don't love Tosca .remember she has never been corrupted by recorded sound .
This is time travel and proves I am no digital hater .
Celestina Boninsegna - TOSCA (1908) - Truesound Transfers - YouTube
You will hear the impossible . If you don't understand you don't love Tosca .remember she has never been corrupted by recorded sound .
This is time travel and proves I am no digital hater .
Dvv, you and I both have some experience of 'what works', and we are not alone.
Bob Cordell has been 'after' Matti Otala for more than 3 decades. He likes to say that Otala was NOT first, that he made mistakes about the necessity of requiring high open loop bandwidth to remove TIM, and that Bob's measurements of PIM, which did not show much, to be the last and final nail that closed the subject.
Well, it isn't exactly all there is, and subjective listening has shown this to be true. We are working on 'objective' tests to show, in future, what we already know by listening.
However, people here will not see this work, before its time, because of the natural resistance to rebut it, out of hand. Hang in there, dvv.
Bob Cordell has been 'after' Matti Otala for more than 3 decades. He likes to say that Otala was NOT first, that he made mistakes about the necessity of requiring high open loop bandwidth to remove TIM, and that Bob's measurements of PIM, which did not show much, to be the last and final nail that closed the subject.
Well, it isn't exactly all there is, and subjective listening has shown this to be true. We are working on 'objective' tests to show, in future, what we already know by listening.
However, people here will not see this work, before its time, because of the natural resistance to rebut it, out of hand. Hang in there, dvv.
No, I did much better than that, I psted a model of what I cinsider capable of becoming a high quality audio amplifier, designed with Otala's principles in mind.
You see, to me, the proof - or not - is in the pudding. If you do smething according to somebody's guidelines, and it ends up working well, then it's safe to assume that somebody's principles are all right when the above happens for the 11th or 12th time in an unbroken row.
And it becomes a bitch to disprove. And the bitch is all yours, Mr Cordell's and whoever else you want to call in.
(Bold and red by DVV)
Scott, that is all and precisely what I have been saying. I do not think of Prof Otala as a Higher Being, an idol or whatnot, simply as a man who walked down a certain path, came to certain conclusions and laid them out for all to see, read and make their own conclusions. I read them, thought about them and concluded that he was right - strictly in my view. You may differ.
I then proceeded to make 11 or 12 units, for various purposes (i.e. not all were power amplifiers), all of which simply convinced me beyond reasonable doubt that Prof Otala was right. Certainly not 100%, nobody is 100% right, but in essence.
Obviously, I did like what I got, or I wouldn't have kept on. Moreover, others liked it as well, so some models slod well, fetching very reasonable prices.
All of which is completely meaningless and irrelevant to you, if you should happen not to agree. We all hear things our own way. Many times I have heard units and entire system which sounded godawful to me, but their owners loved them. So what? We're still friends.
I am too old and too experienced to even think of trying to change peoples' minds, let alone try it. I do NOT understand why is it so important to some people to "prove" Otala's views wrong - if I don't agree and/or like X, I simply ingnore him altogether.
Some people like the priest, others prefer his wife.
Yep , I know about "O" and "A" levels
There you go, Scott. We have now earned the right to address each other as "colleague".
Although, of course, much depends on whose turf you did it, Oxford or Camebridge. Bob Stuart and I are Camebridge men.
Something working well is a necessary condition but not a sufficient one to demonstrate truth. It could be a matter of correlation rather than causation. It could be that X's prescription works (much of the time), but not for the reasons X believes to be true. Any change to a circuit is likely to have several different effects.dvv said:
Let's be clear: my understanding is that the central claim is that Otala et al are wrong (in fact) about certain consequences of feedback theory, not that an amp based on their prescription will necessarily be 'bad'. Therefore any number of amps which turn out 'good' does not prove them right.
John, by now, you must have noticed that formulas and 'scope pictures don't mean diddly to me. What my ears tell me is EVERYTHING to me, with all respect to everybody.
That's not because I think them a waste of time, no, God forbid, we need them as well, but they are not the point, nor the goal, they are SUPPOSED to be simply tools to help us improve ourselves. Take them out of that context, and you may as well stop talking to me.
Specifically here, I have "heard" (read) a lot of theory, but I have seen prescious few of those objections turned into a concrete circuit. Regarding you, I can understand why, but if Thorsten could do it, if I could do it, why can't other scientific philosophers show at least something in aid of what they claim?
My friend of old, Milan Karan, has a great solution for this type of situation. Many times, I have witnessed people coming up to him and asking why did you use that transistor, why not another one, blah, blah. He has developed a response to such people. He simply says (BTW, he is 6'6" and must weigh in at least 300 lbs, a giant of a man, with the widest smile I ever saw): Look, when you show me something you have done with your own two hands, even if it's a variable power light switch, THEN we can talk.
I will gladly change my mode of operation when it is demonstrated by ACTUAL UNITS, not formulas, that Otala is essentially wrong. I believe there is nothing man has done that cannot be improved on, and Otala's theory is no exception. But it has worked brilliantly for me, and I can't think of a single reason why I should change.
So, until something better appears, it's Otala's theory for me. You don't swap a great running and winning horse in the middle of the race.
Ho-hum.
More empty words and phrases. It could be, it might be, it may be ...
Why is this so important to you, DF96? If you feel he's off course, why not simply ignore him? Why is it so important to prove him wrong?
I feel no compunction to prove him right. I think he is, so I do accordingly. And will continue to do so as long it works for me.
If it's that important to you, by all means, lay down your own theory, explaining the right reasons. I welcome any opportunity to learn something new, which will help me be better yet.
It is not at all important to me to prove him wrong, especially as it seems others much smarter than me have already done this. I could ask, why is it so important to you to assert that he is right? I do like truth to emerge from a discussion, as I was brought up to have a deep respect for truth.
Otala has made certain statements. Others (e.g. Cordell) say they are false. The issue there is truth.
Then along comes people who say that following Otala results in 'good' amplifiers so therefore he must be right (faulty logic) or who cares (utilitarianism - its useful even if it turns out to be false). Can you see why this might create a clash with those who are interested in truth?
Otala has made certain statements. Others (e.g. Cordell) say they are false. The issue there is truth.
Then along comes people who say that following Otala results in 'good' amplifiers so therefore he must be right (faulty logic) or who cares (utilitarianism - its useful even if it turns out to be false). Can you see why this might create a clash with those who are interested in truth?
Completely agreed, Scott.
So, what's the current "score"?
Has anyone shown that his views of wide open loop bandwidth is detremental to sound quality?
Has anyone proved that his views on more local and less global NFB is actually wrong? Taste aside?
As a matter of fact, I have proved it to myself beyond any reasonable doubt in the simplest possible form. I built an amp in two versions, one using more local and less global NFB, and another using less local and more global NFB. Then I sat down and listened for a solid month, day in, day out. And concluded that the less global and more local NFB version sounded considerably better, more open, with more "air", detail and space.
Obviously, one topology is hardly any conclusive proof, but since that's the topology I use, it was proof enough for me. A classic, fully complementary Bongiorno type of topology.
In another topology, this might not be so, no matter how much I doubt that, but the difference between the two may well be smaller - but may also be bigger.
I agree with John on this - for reasons I cannot explain, there are people out there who take it as their life's mission to prove one Prof Matti Otala wrong. To me, that's filming "Mission Impossible" for the n-th time because, unlike most purely academics, he pulled off the one magnificent trick which is the hardest to put down. He not only stated what he believed was wrong, but provided a living model to support his theory.
Then he added insult to injury by working for HK for several years, a result of which was the one and only Citation XX. The other long term result have been all of HK's popular products since then, some more, some less. Both my units were built along those lines, and they work like few mass produced items can.
Arguing that this may well be so, but for different reasons, is, to put it mildly, childish and vindictive (I don't mean you, Scott). Throwing a tantrum.
your reading must not have included Cordell - he built amp, and measurement hardware, showed Otala's PIM, "FM" IMD can be low in a high loop gain amp
no hand waving - Hardware
it is important to actually understand the technical issues - the claim that reduced PIM "explains" "good sound" in low, flat loop gain negative feedback amps needs to be tested against high feedback amps with equal (or lower PIM as is in practice unavoidable)
so in any of your listening did you use any high feedback amp with low PIM?
often "simplest possible" comparisons confuse/conflate multiple factors - you really need to design high feedback, low PIM amps from the ground up - not just tweak a VAS load or such
no hand waving - Hardware
it is important to actually understand the technical issues - the claim that reduced PIM "explains" "good sound" in low, flat loop gain negative feedback amps needs to be tested against high feedback amps with equal (or lower PIM as is in practice unavoidable)
so in any of your listening did you use any high feedback amp with low PIM?
often "simplest possible" comparisons confuse/conflate multiple factors - you really need to design high feedback, low PIM amps from the ground up - not just tweak a VAS load or such
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If they can back up their words with hard deeds, I can see it.
Otherwise, on a purely philosophical plane, no, I do not see, nor do I care about the great cosmic truth. I care about what I hear, and what others seem to hear as well, since they are paying their own good money to get it.
If it bothers you that I do as this False Prophet preaches, then by all means, do stop reading my postings.
I never claimed, or believed, otherwise. That's because I ran into exceptions to each and every rule I know of sometime in life.
A general rule is by deafult not absolute, or it wouldn't be general.
Let me phrase it this way - I can get the sound I want easier using Otala's approach that Cordell's. MUCH easier. That's why I use it, but that doesn't make Cordell's approach wrong in the sense that it is impossible to get good sound with it.
Ultimately, look back a few pages to the LAS amp schematic I posted, and reread my comment on it.
We are clearly talking about different things. I am interested in truth. You, by your own admission, are interested in utility. No point in arguing, although it would help communication if you did not express your utility in the form of truth statements. From now on, perhaps I should assume that when someone says "X is right" he may mean "I find X to be useful, so please don't tell me that X is wrong".
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