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Re: Sweetness VS Load Lines

Posted by Tre' (P) on August 11, 2006 at 17:37:32

In Reply to: Re: Sweetness VS Load Lines posted by Naz on August 11, 2006 at 15:57:54:

"Doesn't this part of my statement mean that the remaining 2kHz distortion signal at the OP is still in phase with the 1kHz, matching the statement:

"Tre, 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".'

Yes. Where this is falling down is the idea that the " second tube cancels the 2Khz at its input BEFORE the input signal ever reaches the OP".

A tube is just a varible resistor. The current through the tubes goes up with a positive signal and down with a negative signal applied to it's grid. That current swing IS the OP.

There is no such thing as "before the OP".

A tube just amplifies all the signal at it's input and then adds distortion. If that distortion is the same frequency and in phase with a part of the input signal (at the output) then those two signals add.

One other thing. Two single ended stages, cascaded, are not push pull.

In a push pull circuit both tubes are driving and sharing the same load in opposite phase. And everything that you have been wrongly attributing to a two stage amplifier is true. The operating curves are layed back to back. The "up hump" (egg shape) of one shows like a "down hump" to the other and cancellation of distortion does occur.

I'm sure we would understand (not necessarily agree) each other better if we were face to face. Maybe I need a vacation "down under"? :-)

Oh well, take care. We can solve the worlds problems some other time.

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

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