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Old 4th June 2012, 10:15 AM   #21
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Quote:
Originally Posted by audiodesign View Post
I don't like the cross feedback
What is from your view the main disadvantage by circuit from post #18 in opposite to that one from post #17 ?

The input cascode (at first look a differential amp) from post #17 provides rather an advantage compare with a normal one-stage input section from post #18.
OTOH - crucial should be the audible differences between both solutions.

Last edited by tiefbassuebertr; 4th June 2012 at 10:23 AM.
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Old 9th June 2012, 07:33 AM   #22
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Originally Posted by audiodesign View Post
I have got a copy of Linear Audio magazine - volume 0 (Linear Audio | your tech audio resource) to read the article of Frank Blöhbaum about New Low-Noise Circuit Approach for Pentodes.
I am selling this book
LInear Audio book volume 0 | eBay
In the Frank Blöhbaum article it described only a useless configuration called "best pentode"
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Old 9th June 2012, 07:42 AM   #23
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tiefbassuebertr,
yes the differential is not a bad solution about feedback

Actually I am working to a servo loop to have no dc offset because after some test with the hybrid configuration with mje15032 I have seen a very low stability using only a trimmer.
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Old 15th June 2012, 06:13 AM   #24
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new version in testing phase
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Old 18th June 2012, 06:23 AM   #25
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new version schematic to test and previous version driver stage measurements
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Old 18th June 2012, 09:43 AM   #26
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Some photos
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Old 19th June 2012, 07:16 AM   #27
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last version with driver meaurements
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Old 19th June 2012, 09:53 PM   #28
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Nice project!
Any plans to try the Semisouth JFETs in the output?
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Old 20th June 2012, 08:12 PM   #29
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Quote:
Originally Posted by Nelson Bass View Post
Nice project!
Any plans to try the Semisouth JFETs in the output?
Here two other circlotron topologies:
My JFET project
The Amazing Fet Circlotron by Mike Rothacher

I would try to replace the tube with a VAS stage like this (introduced magic resistor and cascoded cascode):
http://peufeu.free.fr/audio/memory/memory-5-vas.html
This topology must actually clearly beat all exist small signal tubes in all respects, as long as high supply voltage is still present.

Last edited by tiefbassuebertr; 20th June 2012 at 08:20 PM.
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Old 21st June 2012, 07:11 AM   #30
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Quote:
Originally Posted by audiodesign View Post
I am selling this book
LInear Audio book volume 0 | eBay
In the Frank Blöhbaum article it described only a useless configuration called "best pentode"
Why is it useless in your opinion?
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