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Re: Sweetness VS Load Lines

Posted by Tre' (P) on August 10, 2006 at 07:55:16

In Reply to: Re: Sweetness VS Load Lines posted by Naz on August 9, 2006 at 21:17:40:

"The simple answer is that the 2ndH produced by the tube in the second stage is always in antiphase with the signal at its input "

Yes it is. But that does lead to cancellation. What we're interested in is the phase of the distortion from the first stage and the distortion from the second stage as they both appear at the output of the second stage.

You said that the distorion product of a tube is IN phase with the fundamental at the output of a stage.

http://www.audioasylum.com/forums/tubediy/messages/107015.html

So the 2K at the input of the second stage (in our example) is in phase with the 1K at the input of the second stage. They are both out of phase with the input 1K, but in phase with each other as they now feed into the second stage.

The 2K (the distortion of the first stage), will be in phase with the 1K at the output of the second stage. Both out of phase WRT input of second stage, but still in phase with each other.

The 2K distortion of the second stage, at the output of the second stage, will be in phase with the 1K at the output of the second stage.

So the 2K distortion of the first stage and the second stage 2K distortion are in the same phase at the output of the second stage. Both are in phase with the 1K.

You said it yourself.

" in a normal well designed gain stage there should be no phase shift between 1kHz and it's 2nd harmonic as measured at the OP"

Every thing I have said is built upon this statement of your's.

Please forget your preconceived ideas and follow the phases at each stage and you will see that I'm right.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

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