Re: Line Stage Kit - Dave Davenport - K&K Audio / Lundahl Transformers

K&K Audio / Lundahl Transformers

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Re: Line Stage Kit

Posted by Dave Davenport (M) on October 20, 2003 at 07:42:19

In Reply to: Re: Line Stage Kit posted by pushpulltriode on October 20, 2003 at 03:47:49:

Hello PPT,

The crossover distortion that you talk about is a characteristic of the class of amplifier, class-A, Class-B, class-AB, and not the method of coupling. In a class-A amplifier, the tube is always conducting and never cuts off. This is necessarily the mode of single-ended amplifiers. In a push-pull amplifier, the designer often takes advantage of the fact that one side can supply all of the power while the other is cut off for part of the cycle. In class-B each side of the amplifier cuts off for one-half of the cycle while the other half bears the load. In class-AB both are conducting at low levels while one cuts off at higher levels. You could design a push-pull amplifier where each side operates in class-A and never cuts off, so each side is working all of the time contributing to the output. In my opinion the very best push-pull amplifiers are fully class-A. Believing this, of course I designed my Line Stage to be fully class-A so there is no crossover distortion. Think of it as two separate single-ended-triode amplifiers, each amplifying the opposite phase of the signal. A differential output (transformer primary) is taken from the plates of the two SET amplifiers.

The TX102 is an excellent transformer and I considered doing exactly what you suggested. In fact, Lynn Olson and some of his audio companions have tried using the TX102 as an input transformer and phase splitter for a push-pull amplifier. They reported that there was a problem with balance between the two split signals. Therefore I have set that project aside for a while.

There are no coupling capacitors, only a single parafeed capacitor. That capacitor was chosen empirically to provide the best frequency response. With a pair of 6N1P triodes driving an LL1674 I found that a 2uF capacitor was optimum.

Dave Davenport

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Follow Ups Full Thread

Topic - Line Stage Kit - pushpulltriode 02:48:23 10/12/03 (17)

Gain vs. Dynamics - Kuei Yang Wang 11:55:30 10/12/03 (3)

Congratulations!!! - Bas Horneman 05:55:23 10/16/03 (1)

Re: Congratulations!!! - Kuei Yang Wang 23:58:59 10/17/03 (0)

Re: Gain vs. Dynamics - C.Y. 08:58:11 10/14/03 (0)

Re: Line Stage Kit - Dave Davenport 11:29:07 10/12/03 (12)

Re: Line Stage Kit - pushpulltriode 22:30:46 10/12/03 (11)

Re: Line Stage Kit - Dave Davenport 10:22:45 10/13/03 (10)

Re: Line Stage Kit - pushpulltriode 03:47:49 10/20/03 (9)

Re: Line Stage Kit - Dave Davenport 07:42:19 10/20/03 (1)

Re: Line Stage Kit - pushpulltriode 08:56:32 10/20/03 (0)

Re: Line Stage Kit - pushpulltriode 07:24:01 10/20/03 (6)

Re: Line Stage Kit - wiligruen 08:57:54 10/20/03 (2)

Re: Line Stage Kit - Dave Davenport 10:28:10 10/20/03 (0)

Re: Line Stage Kit - KevinC 10:03:51 10/20/03 (0)

Re: Line Stage Kit - Dave Davenport 08:55:28 10/20/03 (2)

Re: Line Stage Kit - pushpulltriode 04:24:22 10/22/03 (1)

Re: Line Stage Kit - Dave Davenport 08:21:35 10/22/03 (0)

Follow Ups

Re: Line Stage Kit - Dave Davenport 07:42:19 10/20/03 (1)

Re: Line Stage Kit - pushpulltriode 08:56:32 10/20/03 (0)

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