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Old 24th June 2008, 06:45 PM   #21
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Hi Darius;
do you remember about amplification?
Without it we have simpler solutions, wit no any active elements at all.
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Old 24th June 2008, 09:36 PM   #22
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Linearly spaced pentode curves? Sorry, no emulating the IGBT!

Besides: G1>Cathode resistance is a negative feedback.
You know the rules about feedback!
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Old 25th June 2008, 07:51 AM   #23
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Default #22

Quote:
Originally #22 posted by kenpeter
...
Besides: G1>Cathode resistance is a negative feedback.
You know the rules about feedback!
Hello kenpeter,
please tell me the diyAudio feedback rules,
I am happy add them to the diyAudio technical forum rules, thanks.

Darius
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Old 25th June 2008, 12:43 PM   #24
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Ignore intrinsic negative feedback. Cathode resistance is evil.
No emulating anything, especially technical forum moderator.
Makebelieve sigline rules apply only to Darius.
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Old 25th June 2008, 01:13 PM   #25
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Quote:
Originally posted by kenpeter
Ignore intrinsic negative feedback. Cathode resistance is evil.
No emulating anything, especially technical forum moderator.
Makebelieve sigline rules apply only to Darius.

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Old 25th June 2008, 04:05 PM   #26
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Default #15 curve shapes

"
Output curve 1 shows a linear resistor.
Curve 2 shows a diode or a triode at negative grid voltages.
Curve 3 shows a pentode, tetrode etc., transistor FET BJT or a triode at
positive grid voltages.
"

Darius, I am a little confused by your hand-drawn plate curves.

You show both the "pentode" and "triode" curves converging at both ends of the resistor curve.

I'm more familiar with the attached curve which shows the plate curves asymptotically parallel with the "resistor" curve.

edit -- what I think the parallel plate curves show is relatively constant plate resistance for different grid voltages in the straight region of the curves, implying at least some of the triode-ness is retained at +ec1

This chart is for a 6F6 though. Maybe different tubes behave differently; I have not tested this myself.

Cheers,

Michael

PS
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File Type: jpg triode plate graph-6f6.jpg (85.0 KB, 206 views)
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Old 25th June 2008, 04:24 PM   #27
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Looks like a load line placed at right angles to the 6F6 plate curves would have fairly constant gain versus grid voltage around -10V to +10V on g1 (would have to deal with the grid current though). But this could be an illusion without some finer measurements. Two obvious counter effects of compression are occuring at larger + and - grid1 voltages, but they may just produce a peaked gain curve at the center (rather than flat), giving odd harmonic distortion.

Don
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Old 26th June 2008, 06:43 AM   #28
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Default #26

Quote:
Originally #26 posted by Michael Koster
"
Output curve 1 shows a linear resistor.
Curve 2 shows a diode or a triode at negative grid voltages.
Curve 3 shows a pentode, tetrode etc., transistor FET BJT or a triode at
positive grid voltages.
"
...

Darius, I am a little confused by your hand-drawn plate curves.

You show both the "pentode" and "triode" curves converging at both ends of the resistor curve.
... Michael

PS
Hello Michael,

see attachment.

Kind regards,
Darius
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File Type: jpg triode plate graph_123-6f6.jpg (74.7 KB, 185 views)
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