John Curl's Blowtorch preamplifier part II - Page 103 - diyAudio
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Old 6th September 2009, 08:37 PM   #1021
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What about letting this discussion rest for a while and find a new topic?

At the moment we are all done and need a break. Itís a very interesting topic so Iím sure (and hope) it will be back on the arena within a couple weeks.

I hope thatís ok by you as well John.

Cheers
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Old 6th September 2009, 09:07 PM   #1022
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The keyword is asymmetry of sidebands. John said that finally.

It reminds me an old story about one professor: "They are dumb! I've explained them, but they did not understand! I explained them once more, but they did not understand! I explained the third time; I even myself understood, but they still did not!!! How dumb they are?!"
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Old 6th September 2009, 09:34 PM   #1023
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Thank you, Wavebourn.
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Old 6th September 2009, 09:38 PM   #1024
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Stinius, everyone wants to 'bail' but not yet. We have to look at which it is: Matti's or Mitch's explanation that is ACTUALLY being measured?
i.e. is it IM or FM(or AM) that is showing up on the graph? It's easy, just do the math yourself and try to fit it to the graph. Rough fits are NOT OK.

Last edited by john curl; 6th September 2009 at 09:52 PM.
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Old 6th September 2009, 09:44 PM   #1025
gerhard is offline gerhard  Germany
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Quote:
Originally Posted by Wavebourn View Post
The keyword is asymmetry of sidebands. John said that finally.

It reminds me an old story about one professor: "They are dumb! I've explained them, but they did not understand! I explained them once more, but they did not understand! I explained the third time; I even myself understood, but they still did not!!! How dumb they are?!"
I heard that Buddha said most people need _many_ explanations how to
achieve nirvana; very wise men would need only abt. 50000.


Is this an acceptable input voltage for the amplifier test?
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Old 6th September 2009, 10:22 PM   #1026
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Quote:
Originally Posted by john curl View Post
i.e. is it IM or FM(or AM) that is showing up on the graph? It's easy, just do the math yourself and try to fit it to the graph. Rough fits are NOT OK.
Rough fit's all you're going to get.

The graph doesn't even fit its own numbers.

I created a simple graph using the numbers given but it doesn't scale so as to fit the published graph.

Click the image to open in full size.

se
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Old 6th September 2009, 10:22 PM   #1027
gerhard is offline gerhard  Germany
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reconstructed test circuit.
The second stage was necessary because the 5K load requirement
prevented getting enough signal into the 50 Ohm spectrum analyzer.
Its influence should be negligible.
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Old 6th September 2009, 10:51 PM   #1028
gerhard is offline gerhard  Germany
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I hate this Canon PowerShot Pro!!!11!!!

The spectrum is close to the one in the paper.
Sorry, I have abused a RF spectrum analyzer.
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Old 6th September 2009, 11:05 PM   #1029
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Gerhard:
Is that the input or the output of the opamps? Or is there an input sensitivity issue preventing looking directly at the input?
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Old 6th September 2009, 11:21 PM   #1030
gerhard is offline gerhard  Germany
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That's the output of the Lt1028.
I could loook at the first op amp with a Tektronix FET probe,
but that has probably to much IMD.

BTW R7 was intended to be 1K only but I won't change this again.

The peaks are at

1.370 KHz
2.270 KHz
3.180 KHz (center)
4.080 KHz
4.990 KHz

(by moving the crosshair cursor)
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