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Old 15th March 2012, 05:01 PM   #11
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That's a lot of B+.....for a preamp....
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Old 15th March 2012, 05:07 PM   #12
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I beleive you are saying both the same thing in different ways.....
http://www.fourwater.com/files/spacecharge.txt
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Old 15th March 2012, 05:23 PM   #13
popilin is offline popilin  Argentina
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Hi DF96
Yes, electron cloud effect is the same as space charge, if you have problems with this, add another grid (tetrode) or elevate +B, if you still have problems add another grid (pentode) or elevate +B and so on.
Electrons that aren't absorbed by anode cotributes to space charge, in my childhood I read that one reason for tetrodes/pentodes was the space charge.
I'm sorry if I'm wrong.
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Old 15th March 2012, 05:33 PM   #14
popilin is offline popilin  Argentina
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Hi jmillerdoc
I didn'n know about Space Charge Tubes, thanks for the paper.
If you see ECC82/12AU7 datasheet, in SRPP connection a +B of 650V isn't a problem.
The idea is minimize the space charge with a more common tube.
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Old 15th March 2012, 05:41 PM   #15
DF96 is offline DF96  England
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Space Charge Tubes is irrelevant. Space charge in ordinary tubes is good, not a problem. It reduces shot noise (Google space charge shot noise smoothing) and protects the cathode from ion bombardment (Google temperature-limited operation cathode poisoning). You certainly don't want to eliminate it.

The transition from tetrode to pentode has nothing to do with eliminating space charge effects. It is all about eliminating secondary emissions effects - the tetrode kink. Some tetrodes deliberately use a space charge to achieve the same result. I think you have been reading the wrong books/websites.
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Old 15th March 2012, 06:14 PM   #16
popilin is offline popilin  Argentina
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Hi DF96
Exactly, that's the same I say in post #13, in your expertise words the effect is called secondary emission and increase space charge.
Space charge is almost impossible to eliminate, so I only try to minimize them.
It's true, space charge in a tetrode prevent secondary emission, but isn't so effective, so you need a pentode.
It seems to me you never done thermionic emission experiment, neither measurement of Planck constant and fight with space charge.
And yes, you are right, you are the genius physicist and I'm the stupid from the third world.
I don't know why you ever criticize all my posts, even if I'm right, may be I live in Argentina? or you are critic by hobby?
It's very difficult to obtain a good advise from you.
Came on, we are at the same planet, and at the same magnificent forum, dont ruin them.

Last edited by popilin; 15th March 2012 at 06:33 PM.
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Old 15th March 2012, 07:20 PM   #17
DF96 is offline DF96  England
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Quote:
Space charge is almost impossible to eliminate, so I only try to minimize them.
No valid reason to eliminate it, as I said. Space charge is good.

Quote:
And yes, you are right, you are the genius physicist and I'm the stupid from the third world.
I don't know why you ever criticize all my posts, even if I'm right, may be I live in Argentina?
Comments like that are too silly to answer. I hadn't noticed what country you are from; it is irrelevant.

If you are saying that you would prefer not to have your misconceptions corrected then that is fine. Most people on here like to learn, including me.
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Old 16th March 2012, 12:25 AM   #18
popilin is offline popilin  Argentina
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Hi DF96
I always thank you for your corrections, you can't say the otherwise.
Your critics are anoying, but make me think and this is good.
Isn't Landau-Lifshitz or Cohen, but can be useful

Electron-cloud effect - Wikipedia, the free encyclopedia

Space charge - Wikipedia, the free encyclopedia

Tetrode - Wikipedia, the free encyclopedia

Is an error suppose that space charge boundary is the grid.
When I measured Planck constant was a dicovery for me how much anoying space charge can be.
If not controlled can distort seriously a straight-line.
I can to look for the paper (It's in spanish) if you wish.
Without Child-Langmuir I knew the reason for nonlinearity in valves at Quantum levels. Planck constant is very little.
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Old 16th March 2012, 12:01 PM   #19
DF96 is offline DF96  England
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Wikipedia tells me that electron cloud effect is something which happens in particle accelerators, not thermionic valves, so this appears to be irrelevant.

Space charge around the cathode does not create distortion, it reduces noise and protects the cathode. It is an essential part of normal valve operation, as I keep saying.

I don't know why you keep mentioning Planck and quantum physics.

There are small numbers which matter: electron charge and Boltzmann's constant. If these were bigger valves would be noiser, but distortion would be unaffected
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Old 16th March 2012, 01:47 PM   #20
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Wikipedia! Come on now....thats your reference source? A library of stuff cobbled together by the mass public....

There are better references out there than Wiki...

Do a little digging a little deeper than Wiki and you wil find that what Popillin is saying is correct. But, again i dont think to guys are too far off the same point.

Basically space charge and electron cloud are the same thing. How can you deny that distortion is not related to linearity in valves?
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