Sound Quality Vs. Measurements - Page 498 - diyAudio
Go Back   Home > Forums > Member Areas > The Lounge

The Lounge A place to talk about almost anything but politics and religion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 2nd May 2012, 06:56 PM   #4971
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
Quote:
Originally Posted by dvv
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.
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.

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.
  Reply With Quote
Old 2nd May 2012, 06:58 PM   #4972
dvv is offline dvv  Serbia
diyAudio Member
 
Join Date: Sep 2004
Location: Belgrade, Serbia
Quote:
Originally Posted by john curl View Post
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.
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.
  Reply With Quote
Old 2nd May 2012, 07:04 PM   #4973
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by dvv View Post

I do NOT understand why is it so important to some people to "prove" Otala's views wrong.
I'm not talking about views or opinions. He presents as an engineer and professional and should be able to take corrections of purely technical points in stride. I think in some cases (in-harmonics and PIM) the words were unfairly put in his mouth.
__________________
"The question of who is right and who is wrong has seemed to me always too small to be worth a moment's thought, while the question of what is right and what is wrong has seemed all-important."
  Reply With Quote
Old 2nd May 2012, 07:04 PM   #4974
dvv is offline dvv  Serbia
diyAudio Member
 
Join Date: Sep 2004
Location: Belgrade, Serbia
Quote:
Originally Posted by DF96 View Post
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.

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.
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.
  Reply With Quote
Old 2nd May 2012, 07:17 PM   #4975
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
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?
  Reply With Quote
Old 2nd May 2012, 07:25 PM   #4976
dvv is offline dvv  Serbia
diyAudio Member
 
Join Date: Sep 2004
Location: Belgrade, Serbia
Quote:
Originally Posted by scott wurcer View Post
I'm not talking about views or opinions. He presents as an engineer and professional and should be able to take corrections of purely technical points in stride. I think in some cases (in-harmonics and PIM) the words were unfairly put in his mouth.
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.
  Reply With Quote
Old 2nd May 2012, 07:28 PM   #4977
jcx is offline jcx  United States
diyAudio Member
 
Join Date: Feb 2003
Location: ..
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

Last edited by jcx; 2nd May 2012 at 07:38 PM.
  Reply With Quote
Old 2nd May 2012, 07:29 PM   #4978
dvv is offline dvv  Serbia
diyAudio Member
 
Join Date: Sep 2004
Location: Belgrade, Serbia
Quote:
Originally Posted by DF96 View Post
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?
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.
  Reply With Quote
Old 2nd May 2012, 07:33 PM   #4979
dvv is offline dvv  Serbia
diyAudio Member
 
Join Date: Sep 2004
Location: Belgrade, Serbia
Quote:
Originally Posted by jcx View Post
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
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.
  Reply With Quote
Old 2nd May 2012, 07:41 PM   #4980
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
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".
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Quality Control differences = variations in sound quality? KT Class D 3 4th June 2014 12:02 AM
Sound Card for Measurements Marik Solid State 2 2nd January 2012 08:59 PM
Sound Card Recommendations (For Audio Measurements) dchisholm Equipment & Tools 5 16th July 2011 09:40 AM
How to protect sound card during amp measurements? okapi Everything Else 13 2nd September 2008 03:06 PM
Sound cards - test and measurements jackinnj Everything Else 2 5th July 2003 03:02 PM


New To Site? Need Help?

All times are GMT. The time now is 03:48 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2