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Old 16th September 2008, 10:21 AM   #11
SY is offline SY  United States
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I'm impressed that a Dutch guy knows Lewis Carroll!
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Old 16th September 2008, 12:35 PM   #12
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Quote:
Originally posted by SY
I'm impressed that a Dutch guy knows Lewis Carroll!

It's impressive that anyone still living knows Lewis Carroll...
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Old 16th September 2008, 01:25 PM   #13
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I had considered driving G1 from the lower 533R, but I didn't have
a published set of curves to say exactly what might happen. It was
not my intent to hand Zob a design I couldn't be reasonably sure
would work on the very first try. There is room for later experiment.

Nobody has complained yet that I use too many capacitors?
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Old 16th September 2008, 01:37 PM   #14
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Default coupling triode

Quote:
Originally posted by kenpeter


Nobody has complained yet that I use too many capacitors?
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Old 16th September 2008, 01:39 PM   #15
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Quote:
Originally posted by Wavebourn
I am going to try a double-drive such a way:
1. Differential phase splitter,
2. 2 asymmetrical Concertinas (higher value of resistors in anodes) coupled to each anode of a diff stage directly;
3. Source followers from their anodes to screen grids of output pentodes,
4. Capacitive coupled cathodes of Concertinas to control grids of output pentodes.
The result should be kind of opposite to UL mode.
If you find yourself needing to adjust the overall amount of UL,
resistive plate to plate (output plates back to the concertinas)
feedback might be handy.
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Old 16th September 2008, 01:50 PM   #16
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Default triode transformer current multiplier arrangements

Hi kenpeter,
I am sure this is helpful for you: triode transformer current multiplier arrangements

Kind regards,
Darius
http://oldeuropesblogs.blogspot.com/
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Old 16th September 2008, 01:59 PM   #17
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Quote:
Originally posted by HollowState
I have seen threads about this paralleling of grids before and just shook my head and kept silent. This is not the way a tube was designed to be used. To make a triode out of a tetrode or pentode, the screen gets tied to the plate. That is the proper way. And in so doing, the gain characteristics of the tube are changed such that the screen can operate at a higher voltage because it is in league with the plate and has less controlling effect. Screen and control grid do not get connected together. This is the way I was always taught.

Yet every so often people will go against the grain and try making a triode by tying them together. Has no one told them that is incorrect? That the usefull characteristics of a tube are destroyed? Perhaps I am too set in my ways and too old to learn new tricks. But I think not. IMHO using a tube in this maner is about as cockamamie as inverted tube operation. Maybe it's the fun of doing something one shouldn't or the joy of an exercise in near futility. I just don't know.

Ok, end of rant.
Victor

the Tung-Sol 3D21W delivers g1=g2 curves on the data sheet. Admittedly not too useful looking, but if you trace them, they will come.
cheers,
Douglas
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Old 16th September 2008, 02:11 PM   #18
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Quote:
This is not the way a tube was designed to be used......Perhaps I am too set in my ways and too old to learn new tricks.
As I have been told before, every possible connection that could be done with tubes has been done already. I remember seing a schematic a long time ago that ran 807's with G1 and G2 tied together in "class B" mode. This is where I got the idea. I can't find the schematic on the web but I have a paper copy somewhere.

Quote:
I am going to try a double-drive such a way.....I would suggest driving g2 directly with a resistive divider down to g1, so that each grid has drive voltage scaled to 1/gm.
OK, why not one typical P-P driver with each output feeding a pair of mosfet drivers (4 total). Each mosfet has independent gain and DC bias adjustments.
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Old 16th September 2008, 02:24 PM   #19
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Type 46 was also double grid drive too. For a three tube amp, one with g2 to anode as the input tube feeding a phase splitting driver TX, and two Class B finals grids tied together.

given that I kknow of two...there must be more...
cheers,
Douglas
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Old 16th September 2008, 02:42 PM   #20
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Hi Tubelab,

Quote:
I remember seing a schematic a long time ago that ran 807's with G1 and G2 tied together in "class B" mode.
Maybe you mean the schematic as attached below.

The "current trickler" configuration you get by connecting g1 and g2 together makes pretty much sense in such a zero bias class B design. Probably just decent enough for train platform public adress systems... at least such a design has its merits regarding power-efficiency, when no drive signal is applied...

Regards,

Tom Schlangen
Attached Images
File Type: jpg 807pp_6l6g.jpg (33.0 KB, 720 views)
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