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Old 4th September 2009, 01:17 PM   #931
iko is offline iko  Canada
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Oh no, I don't think of you, as a person, as repulsive; in all honesty, I don't know who you are, we never met, we never spoke. I was only talking about the way you addressed other people in this thread. To your defense though, quite a few people addressed you likewise. I think it's the tone of the discussion that sometimes very much puts me off. As an outsider one gets the impression of little people squabbling, and I know you are not.

Anyway, the fact that you're sharing some of your knowledge is nice. At times it looks like you guys are almost trying to do some research.

I actually think that the people you mention might not want to contribute here because there's little in it for them. What can they get out of posting in these forums? If they wanted to collaborate with well known technical guys, they can be found in other places. If they wanted to teach other people about their great knowledge, they'd either write books, or articles for publication. And probably one other factor; they want to be paid for their time, and I see absolutely nothing wrong with that. It can take lots of time and effort to develop ideas and products. We can't expect everyone to be charitable or to have the same business model as Nelson Pass. Freebies are nice but I wouldn't want it if I knew it was taken from time with his family and kids. Hence I do appreciate the effort you put here; hard to tell what you're trying to do sometimes. But yeah, it'd be nice if everyone put attitude aside and stay focus on the ball.

And here ends my zero contribution, thank you all
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Old 4th September 2009, 01:20 PM   #932
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Well stated Pooge, at least you have clued me in as to your concerns.
First, I shown something, previously ignored in my own measurements.
Two, I have attempted to share my previous oversight and access its importance to audio design.
Three, as I stated to an 80+ year old man, who knows 100 times more than me on this subject, just last night, that I wished that I had studied my complex math better in school, so that I could more easily absorb FM modulation theory and be able to 'prove' its presence to my colleagues here.

Has anyone come to my aid on FM theory? I don't think so, even though we have some PhD's out there.
Bessel functions are a mathematical term, nothing more. This is not 'name dropping', any more than mentioning something regarding Hertz or Ohm are name dropping. Should I convert to 1000 cycles/second, rather than 1000 Hz, in order not to mention a famous name?
Kind of absurd, isn't it?
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Old 4th September 2009, 01:31 PM   #933
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Iko, your contribution has been significant to me.
It reminded me of my background, how I was raised, and why I don't so mind the 'rough and ready' dialogue of the bickering on this thread, compared with many others, perhaps raised differently.
I note that you come from Canada.
I haven't been to Canada for more than 55 years, but I remember 3 summers there, living on a horse race track with my father in Vancouver, BC. You should have heard the language spoken there, and then you might understand that words are just words to me and I am fairly immune to being 'shocked'. Your sensitivity is probably very different. I have to continually remind myself of this, in order not to through everything out, because of the sensitivity difference.
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Old 4th September 2009, 01:33 PM   #934
jam is offline jam  United States
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I am with ikoflexer here........sometimes you might not like Mr.Curl's attitude (believe me, I have been on the wrong side of it a few times ) but I have learnt a lot from him.

Most of you armchair quaterbacks need to stop and consider that there might something to be learned here , or maybe trying to prove your own credentials is more important. If you disagree with Mr.Curl you are free to leave or better still prove him wrong with your own experiments. Sniping at him does no one any good and is counterproductive.

Mr.Curl has taught me a lot and almost always has been correct but always admitted when he has made a mistake or made a wrong turn..........something which most of his critics won't do. If you have concrete experimental proof that he is wrong ,please present it..........my bet is that he will be the first to acknowledge it. Let's make this discussion constructive for the benefit of all.

Now if we can only get Mr.Curl to Charm School.............

Jam
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Old 4th September 2009, 01:42 PM   #935
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I'm too old for Charm School, but I will hire you to be my spokesman, first chance I get.
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Old 4th September 2009, 02:10 PM   #936
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[QUOTE=john curl;1915445]
I have been shown that these are FM products, NOT IM products. How do we know? We know, because these products are NOT harmonically related to the test signal components and appear is completely unrelated to the test signal itself. [QUOTE]

I posted a link to a fairly easy to read derivation of an FM signal yesterday and I will repeat this is just plain wrong. Your measurement could be contaminated by mains or any subharmonic (FL lights have a spectrum out to over 3000Hz BTW), any horizontal or verticle display frequency, and ALL their subharmonics. I have a test CD from SONY labs that is clearly contaminated with 15,750Hz (made under strict laboratory conditions).

I am reminded of cold fusion results, or maybe some of the free energy presentations.

You should also chose what you say more carefully, think for a second how the claim that the output has no relation to the input sounds.
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Old 4th September 2009, 02:14 PM   #937
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Quote:
Originally Posted by john curl View Post
Anatech, I really don't need this, and you, a moderator too.
The problem is with an intimate understanding of FM modulation, how it happens, what it looks like on a spectrum analyzer. I only have a partial understanding of this, so I am reluctant to 'teach' others about it. Yet, I have 'hit the books' and maybe the test equipment in future, to get a better understanding, so that I can even teach a wider audience, what we have found.

Hi John,

We probably have a bit of a case here of the blind leading the blind. I suspect that you and I are equally ignorant of the details of fm. We each perhaps know enough (or think we know enough) to be dangerous.

I would really like to have somebody more knowledgable step in here and explain how fm with very small deviation creates inharmonic spectral lines. I was always taught that narrowband fm is essentially like am but with the phase of the sidebands just different. I completely understand that this is not the case for high-deviation fm, where Bessel functions are essential to a proper understanding (but I do not believe that PIM falls in the category of high-deviation fm).

All of this does not mean that we should not ask each other tough questions. All of this does not mean that the person making an initial assertion should not back it up as much as possible and try to directly answer the tough questions.

This kind of interchange is how we all learn, including both those more experienced and those who are less experienced.

There are many things you and I disagree on. Those discussions have always challenged my thinking. What doesn't kill you makes you stronger. I have probably learned more from discussions (and arguments) with you than from most any other people. In some cases it is self-taught in trying to examine arguments to put forth myself in those discussions. I can say exactly the same thing about Matti. I certainly did not agree with many of his assertions, but I learned a lot from him and a lot from challenging him.

So let me ask a few direct questions.

Do you agree that what we are dealing with in PIM in at least semi-decent amplifiers is essentially narrowband fm? If not, why not?

Do you agree or disagree that the application of Bessel functions is necessary to gain an even decently approximate understanding of narrowband fm?

How can Bessel functions create in-harmonic spectral lines?

How do you know the EXACT frequency of that blip. It would seem to me that you would have to know that frequency with fairly high precision to know that it is not an N/M frequency (even if you did not EXPECT it there).

In how many other DIM tests did you see the presence of this frequency component that you did not "expect"?

You personally may not know the answers to some of these questions. That's OK, but I would still like you to let us know what you think the answers might be. Even more importantly, if you have been discussing this topic with others much more strongly versed in fm theory you should be able to get those answers from them and relay them accurately to us.


Cheers,
Bob



The 'smoking gun' is FIG. 3 of my Matti's and my AES paper on TIM. It is OBVIOUS from looking at the measurement, that there are extra distortion products that DO NOT REPRESENT what we would EXPECT from the test itself. Not knowing what they were, we just IGNORED them. After there was plenty of other distortion products in the same figure that showed what we were trying to measure and point out, at the time.
I have been shown that these are FM products, NOT IM products. How do we know? We know, because these products are NOT harmonically related to the test signal components and appear is completely unrelated to the test signal itself. Any engineer would get nervous over this, because that is not supposed to happen.
All I can ask of anyone or everyone, is to read up on IM distortion products, before telling me that I don't know what I am talking about. That is all I ask here.
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Old 4th September 2009, 02:20 PM   #938
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Good questions, Bob. I will get back to you, but now I think that I need to get back to sleep for awhile.
Scott, please look at Fig. 3 in detail, before making such assertions.
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Old 4th September 2009, 02:34 PM   #939
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Standard text book derivation of an FM signal, the Bessel functions describe the magnitude envelope of the spectra. The frequencies present are all harmonically related to the input.

No, you need to do due diligence in finding the unexpected lines before making extraordinary claims.
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Old 4th September 2009, 02:42 PM   #940
jam is offline jam  United States
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That's Mr.Bessel to you Bob..............dropping names again?

Sorry, I couldn't resist.

Jam

Last edited by jam; 4th September 2009 at 02:45 PM.
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