Wavebourn said:
Hi Wavebourn,
Thanks for your interest in my PIM paper. It and my other papers can be found on my website at www.cordellaudio.com.
I chose to measure the op amps in the inverting mode so as to not muddy the waters with common mode effects. You are definitely right that more interesting distortion effects would have surfaced if the op amps were tested in the non-inverting configuration and/or at gains higher than 10.
Cheers,
Bob
john curl said:
That is certainly not true, John. I do recall saying to someone that Otala's wrong conclusions misled an entire generation of amplifier designers. That was probably unfair on my part.
I am very interested in seeing any new evidence on PIM, when it becomes available. If you have not seen that evidence, perhaps you were a bit premature in declaring victory. I will admit that I was perhaps prematurely skeptical. We're even. Let's see the evidence.
It is still a bit unclear to me whether the new thing is a new way of measuring PIM or whether it includes apples-apples PIM measurements of amplifiers with high and low amounts of NFB.
What was the story on the guy's patent? Were you referring to a patent that he got, or one that he has just filed?
Bob
I point out to others what Bob Cordell has concentrated on: Both TIM and later, PIM.
I might point out that Matti Otala gave his first paper on PIM about 30 years, ago, BEFORE Bob did his work.
As with all research, sometimes it is not complete, even if it is thought to be so, by the researcher and his colleagues.
When Walt Jung pointed out Barrie Gilbert's paper, it showed hope.
Now, I have an associate who has gone further, we shall see.
What is important to me is to see that Matti Otala's legacy remains intact, without post lifetime nitpicking and cheap criticisms.
I both knew and did research with Matti Otala in the 1970's and I knew both the good and the 'not so good' in him. He was very competitive, and pushed me aside on one occasion. Still, I know the effort he put forth, the sound of this little 'Otala' amp, and the repression of his ideas, ultimately not letting him publish in the AES, WITHOUT real cause, except politics, in the 1980's. That's all folks!
I might point out that Matti Otala gave his first paper on PIM about 30 years, ago, BEFORE Bob did his work.
As with all research, sometimes it is not complete, even if it is thought to be so, by the researcher and his colleagues.
When Walt Jung pointed out Barrie Gilbert's paper, it showed hope.
Now, I have an associate who has gone further, we shall see.
What is important to me is to see that Matti Otala's legacy remains intact, without post lifetime nitpicking and cheap criticisms.
I both knew and did research with Matti Otala in the 1970's and I knew both the good and the 'not so good' in him. He was very competitive, and pushed me aside on one occasion. Still, I know the effort he put forth, the sound of this little 'Otala' amp, and the repression of his ideas, ultimately not letting him publish in the AES, WITHOUT real cause, except politics, in the 1980's. That's all folks!
Bob Cordell said:
Spending money to protect simply a measurement technique of something virtually no one is interested in would surprise me.
Juergen Knoop said:
We designers love to see the whole picture to understand better how to implement more optimal solutions. Extrapolating helps a lot to find an optimum.
Bob Cordell said:
Hi Bob;
so, if you have the tool, why not to bring the whole picture on the surface?
I mean, including some very extreme cases of a single-pole compensation, for example. Gain itself does not matter; what matters, open loop gain when the pole is way below 20 KHz.
Isolating a single effect in an unnatural way does little to show what happens in the real world. I prefer to use 'reasonable worst case' that is: A real example of components, sources, etc, pushed to extremes. This is how I found the highest recorded slew rate from a phono stage, that was mentioned in our rebuttal to 'Another View of TIM' by Bob Cordell. This slew rate might not be the very fastest EVER found, but at least, it is representative of what CAN be in the real world.
The reason that Matti went on to PIM is that he came to realize that TIM was not enough to predict the listening differences between amps. He hated the use of the term 'Slew Rate' and even SID, because he felt that SID translated into 'clipping induced distortion' in Finnish. He told Walt Jung this, decades ago, and I had to work to get them to work together. It was some effort, I can tell you, but I knew they were both researching the same thing, and I told them so.
Now, Walt Jung is with Matti and me in that there is something about open loop and feedback that really counts, and it is NOT just slew rate.
We will stick to this, until something better comes along.
The reason that Matti went on to PIM is that he came to realize that TIM was not enough to predict the listening differences between amps. He hated the use of the term 'Slew Rate' and even SID, because he felt that SID translated into 'clipping induced distortion' in Finnish. He told Walt Jung this, decades ago, and I had to work to get them to work together. It was some effort, I can tell you, but I knew they were both researching the same thing, and I told them so.
Now, Walt Jung is with Matti and me in that there is something about open loop and feedback that really counts, and it is NOT just slew rate.
We will stick to this, until something better comes along.
john curl said:
Not to nitpick, but before making this bold statement, have you recently asked Walt Jung and got his permission to quote him in this matter?
Max, the problem here, is the 'blind' leading the 'blind', much like on some other threads. It really is pointless, with so little known or invested in Otala's research history, by so many.
Still, that little Electrocompaniet amp is still a marvel, so somebody did something right, even if by accident. I don't even think that Matti, produced a better design in later years. He was a sophisticated designer, however, far more than most here. I know, because I worked with him on 3 occasions, over the years. However, he was political, and this tends to smear the good, and not just the 'self promotion' or sanctimonious diversion that he sometimes did. Trust me, however, the people who went after him, are just as 'political' and Wavebourn is sticking out like a 'sore thumb' in his attempt to teach us what PIM is.
Still, that little Electrocompaniet amp is still a marvel, so somebody did something right, even if by accident. I don't even think that Matti, produced a better design in later years. He was a sophisticated designer, however, far more than most here. I know, because I worked with him on 3 occasions, over the years. However, he was political, and this tends to smear the good, and not just the 'self promotion' or sanctimonious diversion that he sometimes did. Trust me, however, the people who went after him, are just as 'political' and Wavebourn is sticking out like a 'sore thumb' in his attempt to teach us what PIM is.
john curl said:
No.
It is a case of "familiarity breeds contempt". I, for one, was foolish enough back in the mid '70s to believe he was some sort of "guru". When I read his articles now, I am amazed at both how agenda-driven he was, and the sheer number of errors in his work.
Andy, you might be right about 'mistakes' but I will say this:
When you are a 'pathfinder' you make 'mistakes' along the way, BUT you still find a path. Matti was always supported by a research lab when he was in Europe, including Philips Research Labs, in the early 70's and the Technical Research Centre in Finland where I worked with him on 2 occasions. He ALSO always had other younger, and competent engineers working along side him and helping him write the papers, including me, in one instance. He always got his stuff 'proofed' by others, and for the AES, he got some NASTY feedback from 'referees' on such weighty matters as the difference between 'overdrive' and 'overload'.
Experience shows us that 'Monday morning quarterbacking' is always easier, than playing the game itself. Please keep that in mind.
When you are a 'pathfinder' you make 'mistakes' along the way, BUT you still find a path. Matti was always supported by a research lab when he was in Europe, including Philips Research Labs, in the early 70's and the Technical Research Centre in Finland where I worked with him on 2 occasions. He ALSO always had other younger, and competent engineers working along side him and helping him write the papers, including me, in one instance. He always got his stuff 'proofed' by others, and for the AES, he got some NASTY feedback from 'referees' on such weighty matters as the difference between 'overdrive' and 'overload'.
Experience shows us that 'Monday morning quarterbacking' is always easier, than playing the game itself. Please keep that in mind.
Whoa , did I see a "pitchfork villager" (good one , andy) 😎
To counter the name calling and other "villager" behavior , why not a few more graphical representations combined with discussion to make the concept of PIM more digestible. Good thing this is only HDD space and not on paper. 😀
OS
To counter the name calling and other "villager" behavior , why not a few more graphical representations combined with discussion to make the concept of PIM more digestible. Good thing this is only HDD space and not on paper. 😀
OS
😎 I look forward to it. Hey, your avatar looks like my neighbor.
All we need now is torches..
OS
All we need now is torches..
OS
It does convey the proper mental image , doesn't it ?
The latest interpersonal exchanges have forced me to look around for PIM info...
http://www.angelfire.com/ab3/mjramp/pim.html
A lot of netizen's confuse it with TIM , making for harder search queries .
The author of the above article quantified this effect in his own maths...
http://www.angelfire.com/ab3/mjramp/pimcalc.html
I am still reading and rereading this to try to elevate above the "villagers".
OS
The latest interpersonal exchanges have forced me to look around for PIM info...
http://www.angelfire.com/ab3/mjramp/pim.html
A lot of netizen's confuse it with TIM , making for harder search queries .
The author of the above article quantified this effect in his own maths...
http://www.angelfire.com/ab3/mjramp/pimcalc.html
I am still reading and rereading this to try to elevate above the "villagers".
OS
john curl said:
What about the Dynamic Precision amps bought out by Electrocompaniet recently ?? Does anyone know much about them ?? Are they high feedback designs etc ?
http://www.electrocompaniet.no/news/DP_News.html
Is this a case of Electrocompaniet hedging their bets ??