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SET Asylum Single Ended Triodes (SETs), the ultimate tube lovers dream. |
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In Reply to: RE: another commentary... posted by Tre' on April 30, 2012 at 21:52:36:
Good idea to go through the calculations on this assertion.
You wrote:
"Let's say we have two hypothetical gain stages. Each with a gain of 10 and having only 2nd order harmonic distortion. Let's say the percentage of 2nd order distortion is 10% (each stage).
If we apply 1 volt of 1kHz to the first stage we get 10 volts of 1kHz and 1 volt of 2khz feeding the second stage.
The second stage amplifier the 10 volts of 1kHz to give us 100 volts of 1kHz.
The second stage amplifies the 1 volt of 2kHz to give us 10 volts of 2kHz.
The second stage distorts the 1Khz and gives us 10 volts MORE of 2khz for a total of 20 volts 2kHz.
The second stage also distorts the 1 volt of 2kHz input signal, to give us 1 volt of 4kHz.
What have I missed?"
I will now edit all those lines to correct the errors, one by one:
"If we apply 1 volt of 1kHz to the first stage we get -10 volts of 1kHz (polarity inversion needs a minus sign) and 1 volt MAGNITUDE of 2khz feeding the second stage, phase not found due to not knowing the distortion transfer function completely. It could be -180 degrees, where it is likely. That means we might assume it is actually -1 volts of 2khz midband.
The second stage amplifier with -10 volts of 1kHz then gives us (1)(-10)(-10) = +100 volts of 1kHz. Note two polarity inversions for inverting common cathode stages.
The second stage amplifies and inverts the -1 volt of 2kHz to give us +10 volts of 2kHz.
The second stage distorts the 1Khz and gives us -10 volts MORE of 2khz for a total of a magnitude of (+10)+(-10) = 0 volts 2kHz!"
It gets complicated quickly when the order is increased to calculate % distortion of a single even order harmonic. But you can see that it's doing it quite well to the 2nd order in terms of cancellation.
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Follow Ups
- RE: another explanation... - commentary 22:02:08 05/04/12 (4)
- RE: another explanation... - Tre' 09:53:43 05/05/12 (2)
- RE: another explanation... - commentary 19:16:33 05/05/12 (1)
- RE: another explanation... Editing all of "NEXT QUESTION" reply - commentary 19:38:21 05/05/12 (0)
- I forgot important details in the above explanation. To remove my mistakes... - commentary 02:59:56 05/05/12 (0)
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