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More. Please read

Posted by Tre' (P) on August 9, 2006 at 00:17:27

In Reply to: Re: Sweetness VS Load Lines posted by Tre' on August 8, 2006 at 23:22:34:

From section 4 of Eduardo B. E. de Lima's "Why single ended amplifiers?"

"If two devices have only second harmonic distortion in the same quantity (lets say 1%) what happens if we connect them one after the other ?

The result will depend on the phase of this second harmonic in relation to the fundamental in each of the devices.
............
-If the two devices are just equal, with the same phase relation between the distortion and the fundamental, the result will be a total of 2.0% of 2nd harmonic distortion. [this is what my graphs show]

- A 30° difference in the relation of the 2nd harmonic and the fundamental between the two devices will produce a total of 1.93% of 2nd harmonic distortion.

- A 60° difference will produce a total of 1.73% of 2nd harmonic distortion.

- A 90° difference will produce a total of 1.41% of 2nd harmonic distortion.

- A 120° difference will produce a total of 1.0% (exactly the same distortion as any of the devices alone)

- A 150° difference will produce a total around 0.52% (about half of the distortion of any of the devices alone)

- If there is 180° difference in the relation of the 2nd harmonic and the fundamental between the two devices the sum will be zero 2nd harmonic (yes that is right, in this ideal situation there would be NO 2nd HARMONIC DISTORTION)......."

So if in the first stage the phase relationship between the distortion and the fundamental is 0 degrees (as you have just told me) and the phase relationship between the distortion and the fundamental in the second stage is 0 degrees (as you have just told me) then no canceling takes place. This is what my graphs show.

Common cathode tube stages always invert. This is not at play. You have positive going in and negative coming out. Negative going in (to the second stage) and positive going out. This is not the relationship
Mr. Lima is talking about. I hope that is clear.

What I want to know is how do we know and control the relationship within a stage so we can design to achieve distortion cancellation?

Thanks....Tre'

.
Have Fun and Enjoy the Music
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• distortion and phase   (Open in New Window)

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