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Old 22nd December 2012, 11:08 PM   #11
DUG is offline DUG  Canada
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Gost22:

Three cheers to someone who knows how to put a load line on a plate characteristic graph.

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Old 23rd December 2012, 04:55 AM   #12
Gost22 is offline Gost22  Bolivia
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Hi kevinkr!
CCS in the plate circuit-define what you mean this?
I let the schematic.
thank you!
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Old 23rd December 2012, 05:33 AM   #13
Gost22 is offline Gost22  Bolivia
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Hi all!
How about something like this for source constant current at the cathode?
Or you can offer something better.
thank you!
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Last edited by Gost22; 23rd December 2012 at 05:57 AM.
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Old 23rd December 2012, 06:50 AM   #14
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Read what Kevinkr wrote.
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Old 23rd December 2012, 07:11 AM   #15
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op, why do you want a ccs in the cathode?
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Old 24th December 2012, 07:55 AM   #16
Gost22 is offline Gost22  Bolivia
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Hi all!
Merry Christmas and happy NEW YEAR!
Cheers!
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Old 24th December 2012, 02:57 PM   #17
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What post #9 says. LED in the cathode is all good.

See the 6SN7 stage in the attached schematic.
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Old 24th December 2012, 03:25 PM   #18
EUVL is offline EUVL  Europe
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Just to see if I can find a solution to the problem, without trying to justifying it.

Problem to solve : low noise CCS 7.5mA at 2V headroom.

Proposed solution :
5x heavily-degenerated 2SK246BL with matched Idss in parallel,
and 1x 100~125R common source resistor (for all 4 FETs) to generate the negative Vgs as required.
Adjust resistor value to achieve 7.5mA.

Should be lower noise also than a BS170, and without the added complication of an opamp-based circuit.


Patrick
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Old 24th December 2012, 04:30 PM   #19
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Quote:
Originally Posted by zigzagflux View Post
What post #9 says. LED in the cathode is all good.

See the 6SN7 stage in the attached schematic.
Do you have a drawing of or can you describe the CCS you used for the 6SN7? I didn't see it on the drawing.

My new years resolution is to build a 6SN7 stage with a horizontal load line to drive an 845 transmitter triode. I have some DN2540s on order now but am still reading up on the subject and am interested in other schemes.

Last edited by Captn Dave; 24th December 2012 at 04:56 PM.
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Old 24th December 2012, 05:00 PM   #20
kevinkr is offline kevinkr  United States
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Take a look at SY's "His Master's Voice" article for a good example of the cascode CCS I am thinking of: His Master's Noise: A Thoroughly Modern Tube Phono Preamp
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