John Curl's Blowtorch preamplifier part II - Page 102 - diyAudio
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Old 6th September 2009, 06:23 PM   #1011
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It is not BS, it is an error. Whether Matti made an error in presuming that a certain group of pips were caused by 2F-N IM, or Mitch Cotter allegedly made an error by seeing the same pips as FM, both were trying to find the 'truth' in the matter.
One thing that 'irks' me, and has for years, is that nay sayers can say NO to just about anything, and IF they are wrong, we are all supposed to shrug our shoulders and go on.
However, if I, or one of my colleagues, in pursuit of new knowledge, goes down the wrong path, or our 'hypothesis' doesn't pan out, we are vilified as BS'ers, troublemakers, and time wasters by the mob. Give it a break, will you? I can't personally PROVE everything, and I don't have the strength or interest to teach the basic stuff that has already been researched.
I can only offer 'audio wisdom' or whatever it is, at this point in my life. If that is not enough, or no one wants to take me seriously, then my time to contribute here is done.
I, too, have better things to do, at least that is what my associates tell me.
By the way, Jan, interesting amp you are making. We are not taking the same approach in our new amp, so we have no conflict, but now I understand your further interest in my new amp. Sorry, our schematics are still secret and patent protected. Take it, or leave it. Most likely, I will be doing a 'dog and pony' show with the amp at Denver Rocky Mountain, in Oct. Depends on the doctors clearing me to travel, by then.
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Old 6th September 2009, 06:49 PM   #1012
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Quote:
Originally Posted by john curl View Post
It is not BS, it is an error. Whether Matti made an error in presuming that a certain group of pips were caused by 2F-N IM, or Mitch Cotter allegedly made an error by seeing the same pips as FM, both were trying to find the 'truth' in the matter.
OK, understood.

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Originally Posted by john curl View Post
[snip]One thing that 'irks' me, and has for years, is that nay sayers can say NO to just about anything, and IF they are wrong, we are all supposed to shrug our shoulders and go on.
However, if I, or one of my colleagues, in pursuit of new knowledge, goes down the wrong path, or our 'hypothesis' doesn't pan out, we are vilified as BS'ers, troublemakers, and time wasters by the mob. Give it a break, will you? I can't personally PROVE everything, and I don't have the strength or interest to teach the basic stuff that has already been researched.[snip]
John, you are calling this off on yourself. Nobody is singling out you or your associates. But can't you get it through your scull that people WILL NOT accept an offhand remark like 'it's FM', and then when asked why, get some tapdancing like 'because Mitch told me and he worked for Marantz' or 'because Jack Bybee took me to lunch and he has a Bentley'. All totally irrelevant stuff, and only reinforcing the impression that you just blabber out something. I'm not saying you do, I'm saying you project that impression.

Edit: I'll get out of here. There's no point, and I don't want to project the impression I'm hunting JC. I'm not.

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Last edited by jan.didden; 6th September 2009 at 06:52 PM.
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Old 6th September 2009, 07:09 PM   #1013
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Before you go, Jan, PLEASE note the SYMMETRY or lack of it, of the pips that you labeled, and then recheck your math and the predicted frequencies of the 2F-N products that YOU put into the graph, and see if they ARE symmetrical as well. They aren't, by my calculations, how about yours? Did I overlook something?
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Old 6th September 2009, 07:20 PM   #1014
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Quote:
Originally Posted by john curl View Post
Before you go, Jan, PLEASE note the SYMMETRY or lack of it, of the pips that you labeled, and then recheck your math and the predicted frequencies of the 2F-N products that YOU put into the graph, and see if they ARE symmetrical as well. They aren't, by my calculations, how about yours? Did I overlook something?
John, they all line up. That's just the way it is. Let go of it and move on. I will also move on, the peanut gallery is agitated again and they should find peace.
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Old 6th September 2009, 07:54 PM   #1015
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I'm done too. There's no value in this debate.
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Old 6th September 2009, 07:58 PM   #1016
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I don't think so, check again. Please look carefully, this time at 2f2-8f1, and 2f2-6f1. Symmetrical to 2f2-9f1, and 2f2-7f1, respectively? I think not. Yet, the frequencies on the graph are symmetrical. Look, I don't mind being proven wrong, just do it properly. This is now between Mitch and Matti, I am only the messenger.

PS. Jack Bybee says hi!

Last edited by john curl; 6th September 2009 at 08:04 PM.
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Old 6th September 2009, 08:04 PM   #1017
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Hi John,
Quote:
It is difficult to separate AM from FM in the graph by anyone, that can be absolutely proven, without completely emulating the test.

Sooo, you're telling us that no one inspected the signal fed to the spectrum analyzer with an oscilloscope at the time? Good lord man! I'd think the very most important thing any researcher (especially one at the engineer level such as yourself) would do is to verify what it is that they are measuring. An oscilloscope would have clearly showed the presence of AM modulation, as I'm sure you are well aware.

Given the fact that you are somewhat unsure of what the graph is indicating, you would want to run that test again. Just so you could appear to know what you are pointing out to us. Maybe some time I will do this. I'll have to set up another signal generator so I can exactly duplicate what you fellas did way back when. I even have some 741s hiding out somewhere here. If you could, can you sketch out your test setup? I'm not exactly sure how you guys mixed the two signals at the time and I would like to exactly recreate your setup. Did you use a selective voltmeter, or a spectrum analyzer? My bet is on the selective voltmeter, but I'd like to be sure.

Again John, why wasn't the LM318 tested? It's absence is a glaring one.

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One thing that 'irks' me, and has for years, is that nay sayers can say NO to just about anything, and IF they are wrong, we are all supposed to shrug our shoulders and go on.
Then you should be able to understand why others are irked when you come out with a statement and use every trick in the book to avoid providing any proof. No one is chasing you John, you are merely being asked to back up your statements. In fact, we are even being polite about it.

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However, if I, or one of my colleagues, in pursuit of new knowledge, goes down the wrong path, or our 'hypothesis' doesn't pan out, we are vilified as BS'ers, troublemakers, and time wasters by the mob.
Actually, that is patently untrue. Your statement reflects exactly what you do if someone else makes a statement in your presence that you want to pick apart. Stop throwing bricks my friend, you do live in a glass house as it were. If you'd like to have an error slide, try admitting to it and allowing others to err as well. Otherwise you, will tend to receive the treatment you give others.

If you'd rather, you can email me a sketch of the test setup. I will then send you a sketch of the test setup as I have constructed it for your inspection. I can even take a picture if you'd rather. Then I'll run the experiment and we can talk back and forth in order to confirm it's done right. I am happy to report the actual results without drawing any conclusions at all. I'll be more than happy to allow those with a professional background to assess what is going on. It may take me some time, but we can get through this. John, I am absolutely sincere about my offer.

If you have a problem with me doing this, pick someone else. Either way, let's get some results you can be sure of. No one has to be embarrassed by returning to some earlier work to verify everything. Sound good to you John?

Anyone else interested in re-examining this critical work? I'm sure we'll come out with the same findings as the original tests, they were conducted carefully so as to withstand peer review.

-Chris
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Old 6th September 2009, 08:07 PM   #1018
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For everyone else, it is important to do the math and calculate what Jan (and even Matti) thought these pips to be, and then compare them to the real measurements on the graph, and check through interpolation between the measured points if the measurements exactly match the calculations. It's high school math!
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Old 6th September 2009, 08:16 PM   #1019
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We tested just about everything, Anatech. We published maybe 1000th of the actual measurements done at the time. I personally took home a stack of several inches thick of measurements, done by myself.
The 318 is fast, so it doesn't show TIM effectively. It appears to have other problems. We later proved, in fact, that any slew rate of 5V/us or more for a preamp, was probably good enough, but that was a few years later. THIS paper was to show a TEST PROCEDURE to measure TIM. We used our most obvious examples to prove it to measure what it is supposed to measure.
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Old 6th September 2009, 08:28 PM   #1020
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Hi John,
Thank you for the explanation. That's all I really asked for. You have to admit, mentioning this device in the text, then excluding it does make people wonder. It appeared as a device that would support the statements made in that paper, to have it missing raised questions. I would have thought that including it would show the test itself wasn't creating some of what you were seeing as TIM. A control if you will.

If you don't mind me asking, any idea of the other issues the LM318 had?

I'll assume that stack of data you took home was lost in your fire. Too bad really. I'm sure there must have been a wealth of information in there.

Quote:
We later proved, in fact, that any slew rate of 5V/us or more for a preamp, was probably good enough, but that was a few years later.
Walt Jung actually stated that the needs were more modest than that even. That was in his earlier book around that time. I would agree with that depending on how high you wanted your frequency response to go.

As for high school math, I have no wish to revisit that experience. Math was not my strong suit and I avoid it if possible. I also see working things like that out as a waste of time. If you're wondering, I really hate fishing!

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