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Thanks

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Tre'

In Reply to: RE: A lot depends on where the screen tap is placed. posted by elblanco on October 11, 2024 at 18:19:14

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I assume that when he uses the term "ultra-linear" he is meaning that the input signal is limited so as to not drive the tube into it's non-linear regions (near cutoff and near saturation)? Having nothing to do with an ultra-linear output transformer (as developed by David Hafler and Herb Keroes who started Acrosound ) having screen grid taps so that a pentode ( or beam power tube) is operated some where in between pentode and triode?
I think his words and this graph prove that. Notice the absence of "ultra-linear' operation.

Edit, I received answer to my question about his use of the term "ultra-linear" and I am correct.

That aside, he is saying the exact same thing I have been saying. He does a better job than I do.
By the way (and just for fun) I love that when he says "we need a true triode" he holds up a 6b4g. That's what I listen to! :-)

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

Edits: 10/11/24 10/11/24 10/11/24 10/12/24

Follow Ups:

RE: Thanks - elblanco 11:37:21 10/14/24 (0)
sorry.

no, he doesnt mean the H&K UL.

just short stroking the output tube to minimize distortion.

BTW, its been a long time , but the only UL amp I ever heard that sounded right had those Acro TO-300 in them.
RE: Thanks - PakProtector 06:26:37 10/14/24 (0)
Those are not particularly evenly spaced. Draw a circle centered on the idle point... :)

I have one on the boards not that is... :) from idle, +40V on the grid gives a delta V anode of 500V, and 40 vots negative changes V anode by 450. That is pretty fine IMO...:)

Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
RE: Thanks - elblanco 13:47:26 10/12/24 (4)
I think Ive posted this before.

turns everything upside down
- 3d tube graphs show the hidden monster (Open in New Window)
- I believe that is just.... - Tre' 16:32:33 10/12/24 (3)
  another way of looking at a dynamic curve.
  In 2D, once you pick your operating point and plot your load line, you can then plot a dynamic curve (transfer function curve).
  
  Here's a tube that is not very linear, with an operating point (and load line) that are chosen poorly making things worse.
  
  The non-linearity of the tube, coupled with poorly chosen operating points, cause one half of the wave form to be exaggerated and the other to be truncated.
  If the tube's operation were linear the ellipse would be symmetrical. Because of the distortion the ellipse is egg shaped.
  
  Tre'
  Have Fun and Enjoy the Music
  "Still Working the Problem"
  - https://www.youtube.com/watch?v=AYZvgAKpb38 (Open in New Window)
  - RE: I believe that is just.... - elblanco 16:53:35 10/12/24 (2)
    but its super cool.
    
    I have that Preisman book and it always winds up being low and hot is best.
    
    and not necessarily the flatness of dynamic line.
    - Low and Hot? - FlaCharlie 07:47:03 10/14/24 (1)
      I've seen operating points described like this many times over the years and always found it vague and confusing. I'm never even sure if those who use these terms even mean the same thing.
      
      Does "low and hot" mean lower voltage and higher current or does it mean lower current and higher voltage?
      - RE: Low and Hot? - elblanco 10:42:34 10/14/24 (0)
        
        In Reply to: RE: Low and Hot? posted by FlaCharlie on October 14, 2024 at 07:47:03
        
        yes. lower voltage higher current.

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