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Old 5th September 2009, 05:10 PM   #991
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Quote:
Originally Posted by Steve Eddy View Post
Well, if I'd have known that, I'd have worked much harder this past year at being an even bigger ******* so that you could have netted enough to fly everyone to Hawaii for BAF2010.

se
There's a limit to the size of *** holes. Even for you

jd
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Old 5th September 2009, 05:41 PM   #992
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Extra thanks Scott, for posting that graph. Mitch Cotter asked me to refer to the ITT Reference guide, in order to clarify FM modulation questions that I was asking him over the phone just this week. Unfortunately, mine got destroyed in the firestorm, and I was forced to use another reference, that I put up here (p15-26).
Your graph is even better, although mine would have worked as well.
FINALLY, we are on same page.
Now, what are those extra 'inharmonic' extra pips? Are they AM, FM, or what, and what is the most REASONABLE explanation for them? (Hint, remember your colleague, Barrie Gilbert's findings?)
In any case, they have remained there for 34 years, untouched by any critic or colleague, EXCEPT by Mitch Cotter, who mentioned them to me, just recently, and I tried to put this 'mystery' up for everyone to see and wonder about. Why Mitch? Because he designs FM systems and has done so for the last 60 years, and he is good at noticing these things. Thank goodness. Now, can we discuss this and perhaps resolve it more deeply.
At the same time, as I designed the AD797 in my new Parasound phono stage using your suggestion for pin 8, instead of Dicks' approach, I sincerely hope that my other associate, a design engineer for more than 30 years, finds little or no PIM in that IC. However, I think that it should be tested for, just to know. We already know that it is almost perfect in AM distortion as well as low noise. It is just that nagging feeling that FM distortion could be present in small quantities, at least at a subliminal level.
Now, isn't this worth a look?
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Old 5th September 2009, 06:10 PM   #993
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I have been able to duplicate, at least visually, one set of sidebands, by FM modulating a 3.18KHz sine wave (Fc) with a level controlled amount of 1.8KHz, and I get an amazing correlation to the sidebands on Fig 3. Why 1800 Hz or so, I don't know, BUT it is the same graphical results CAN be shown with this scheme.
I used a Wavetek 166 function generator with an FM input, set at 3.18KHz and an ST oscillator for finding and setting the level at 1800Hz or so.
It should be noted that we usually never go beyond the first order of sidebands although it is easy to do with this test set-up.
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Old 5th September 2009, 06:12 PM   #994
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Originally Posted by janneman View Post
There's a limit to the size of *** holes. Even for you
Ooooh. I love a challenge.

BAF Hawaii 2011, here we come!

se
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Old 5th September 2009, 06:23 PM   #995
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Originally Posted by Steve Eddy View Post
Ooooh. I love a challenge.

BAF Hawaii 2011, here we come!

se


Now back on topic pls...
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Old 5th September 2009, 07:12 PM   #996
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Quote:
Originally Posted by john curl View Post
Extra thanks Scott, for posting that graph. Mitch Cotter asked me to refer to the ITT Reference guide, in order to clarify FM modulation questions that I was asking him over the phone just this week. Unfortunately, mine got destroyed in the firestorm, and I was forced to use another reference, that I put up here (p15-26).
Your graph is even better, although mine would have worked as well.
FINALLY, we are on same page.
Now, what are those extra 'inharmonic' extra pips? Are they AM, FM, or what, and what is the most REASONABLE explanation for them? (Hint, remember your colleague, Barrie Gilbert's findings?)
In any case, they have remained there for 34 years, untouched by any critic or colleague, EXCEPT by Mitch Cotter, who mentioned them to me, just recently, and I tried to put this 'mystery' up for everyone to see and wonder about. Why Mitch? Because he designs FM systems and has done so for the last 60 years, and he is good at noticing these things. Thank goodness. Now, can we discuss this and perhaps resolve it more deeply.
At the same time, as I designed the AD797 in my new Parasound phono stage using your suggestion for pin 8, instead of Dicks' approach, I sincerely hope that my other associate, a design engineer for more than 30 years, finds little or no PIM in that IC. However, I think that it should be tested for, just to know. We already know that it is almost perfect in AM distortion as well as low noise. It is just that nagging feeling that FM distortion could be present in small quantities, at least at a subliminal level.
Now, isn't this worth a look?
John,

Those unlabeled blips near 1 kHz and 5 kHz appear to be at 1.38 kHz and at 4.98 kHz, being the 2f2 - 9f1 and 11f1-2f2 combinations. The blips lie +- 1800 Hz about the 3.18 kHz carrier.

They are harmonically related to the test tones, and are definitely in the category of expected spectra for this test, especially when one is pounding the cr@p out of a 741, driving it essentially to slew rate limiting with even the 30 kHz filtering.

BTW, it was unclear in my reading of the paper whether the test for Figure 3 was using 30 kHz or 100 kHz; I suspect and assume 30 kHz, but I could not find where it was stated.

The authors themselves stated the following: "... the measurement result of the popular operational amplifier uA741, which represents a case of very strong dynamic intermodulations, where also second-order products such as 2f2 +/- nf1 ... rae generated. Traces of these can be found in Fig. 3." The authors did not label these traces that you seem to think are mystery blips. Not a single 2f2 spectral line is labeled in Figure 3.

No mystery here.

Cheers,
Bob
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Old 5th September 2009, 07:16 PM   #997
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This looks remarkably like spinning side band contamination of an MRI spectra.

http://www.diyaudio.com/forums/attac...1&d=1252100293

OK, that was suppose to be a picture.

Try here.

John Curl's Blowtorch preamplifier part II

Last edited by Steve Dunlap; 5th September 2009 at 07:21 PM.
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Old 5th September 2009, 07:34 PM   #998
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Point well taken, but look at the levels, are they not a little too much to ignore? I would have to do the entire test over, just to be sure, because the actual waveform frequencies are guessed at (by Janneman, I presume), and not measured. Also, we don't have the spectrum changes with level, that are not put on the paper. This is unfortunate, because I did many of the tests, myself, and this would bring out any real deviations.
However, I give it over to you, that the added IM byproducts 'could' be accounted for, perhaps. I still am not sure about this, because FM modulation of the the fundamental test frequency would create the same sort of symmetrical sidebands. Perhaps, my other associate will resolve this dilemma in a few months (that is what he told me, last week) when he decides to show me how to measure PIM by HIS method.
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Old 5th September 2009, 07:47 PM   #999
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Quote:
Originally Posted by Bob Cordell View Post
John,

Those unlabeled blips near 1 kHz and 5 kHz appear to be at 1.38 kHz and at 4.98 kHz, being the 2f2 - 9f1 and 11f1-2f2 combinations. The blips lie +- 1800 Hz about the 3.18 kHz carrier.

They are harmonically related to the test tones, and are definitely in the category of expected spectra for this test, especially when one is pounding the cr@p out of a 741, driving it essentially to slew rate limiting with even the 30 kHz filtering.

BTW, it was unclear in my reading of the paper whether the test for Figure 3 was using 30 kHz or 100 kHz; I suspect and assume 30 kHz, but I could not find where it was stated.

The authors themselves stated the following: "... the measurement result of the popular operational amplifier uA741, which represents a case of very strong dynamic intermodulations, where also second-order products such as 2f2 +/- nf1 ... rae generated. Traces of these can be found in Fig. 3." The authors did not label these traces that you seem to think are mystery blips. Not a single 2f2 spectral line is labeled in Figure 3.

No mystery here.

Cheers,
Bob
You're welcome:

John Curl's Blowtorch preamplifier part II

jd
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Old 5th September 2009, 07:51 PM   #1000
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Originally Posted by john curl View Post
Point well taken, but look at the levels, are they not a little too much to ignore? I would have to do the entire test over, just to be sure, because the actual waveform frequencies are guessed at (by Janneman, I presume), and not measured. [snip].
It's all in the paper, John. It sometimes pays to read your own paper from time to time; your memory can play dirty tricks on you after so many years.

jd
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