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Origin of the so-called "Blumlein Garter"
Origin of the so-called "Blumlein Garter"
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Old 12th October 2017, 08:28 AM   #31
Merlinb is offline Merlinb  United Kingdom
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The nice thing about cross-coupled cathode bias is that it almost guarantees matching idle currents no matter what the gm is. This is great for tube rolling -you can make a PP output stage that will take loads of different tube types with no adjustment necessary, even dissimilar tube types if you're feeling wacky!

Personally I wouldn't call it a 'Davis' anything. It's just cross coupled, with different iterations produced by different people. Broskie does have a habit of making up new names for common things, but then, the man thinks current flows the wrong way so

All credit to Stephen Keller for hunting out the earliest patents. The man's a blood hound.
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Last edited by Merlinb; 12th October 2017 at 08:36 AM.
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Old 12th October 2017, 08:53 AM   #32
jazbo8 is offline jazbo8
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Quote:
Originally Posted by Merlinb View Post
Personally I wouldn't call it a 'Davis' anything
Anything is better than "Blumlein"... At least it is in the ballpark. Were you able to get the full copy of the Martens patent? Google only shows the synopsis.
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Old 12th October 2017, 09:01 AM   #33
Merlinb is offline Merlinb  United Kingdom
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There are more things in heaven and earth, Horatio, than google...
https://worldwide.espacenet.com/publ...R=64203E&KC=E#

Last edited by Merlinb; 12th October 2017 at 09:15 AM.
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Old 12th October 2017, 09:05 AM   #34
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Got it, thanks!
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Old 13th October 2017, 05:55 AM   #35
jazbo8 is offline jazbo8
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Reading both the Davis and Martens patents, it seems that Martens' is more relevant to the garter concept.
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Old 22nd January 2018, 12:44 PM   #36
Lingwendil is offline Lingwendil  United States
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Stepping in here a little late, I'm glad someone got to the bottom of things and found the original Martens info. I'm a huge fan of this circuit, and getting some concrete info on it's origins is neat.
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Old 26th May 2018, 05:43 PM   #37
gorgon53 is offline gorgon53  Finland
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Funny, I knew this circuit as Blumlein-Garter circuit for ages, long before I ever heard of Broskie
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Old 26th May 2018, 05:47 PM   #38
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It was wrong then, and Broskie probably made the situation worse...
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Old 26th May 2018, 05:49 PM   #39
Lingwendil is offline Lingwendil  United States
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Yup. I sidestep all that skullduggery and simply call it garter bias.

My current EL86 design uses it, and it works great! As does the flea amp in my signature. Past experience shows it's great for low mu types like the 6AS7G as well.

Anybody that is skeptical should definitely try it. It's perfect for bulk lot Russian tubes that may be all over the place in gm. I'm going to work on a PCB design using it on the output stage that will work for EL84 types, good way to use the nice affordable 6p14p, and I might do an octal version for 6V6/6L6 types too.
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Last edited by Lingwendil; 26th May 2018 at 05:52 PM.
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Old 27th May 2018, 03:25 AM   #40
6A3sUMMER is offline 6A3sUMMER  United States
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None of you are newbies, but for their sake: Be sure to put in the grid leak resistors too. And if the one tube is gassy, or if the grid leak resistors are too high of a resistance, then we can remember the old lyric "run run run run runaway".

Incomplete schematics like the one at post # 3 get the newbies in trouble.

I am sure all of what I said now has already been said on this thread, but I started reading it today from the beginning. Could a newbie do that too?

As far as having balanced currents in the output transformer, you can use a couple of current sources for the cathodes with a couple of bypass capacitors. Oh, wait, that may not be true for tetrodes, pentodes, and beam power tubes. That is because the screens of two tubes do not necessarily draw the same current. Oh, are we back to either matched tetrodes, pentodes, beam power tubes. Or you can triode wire them, and the cathode current will equal the screen plus plate current. Or more simply a pair of unmatched triodes (they will have the same quiescent current, even though with signal the unmatched nature of the two will show up). Hmm, I guess there is a reason to use matched tubes.

Last edited by 6A3sUMMER; 27th May 2018 at 03:37 AM.
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