Vacuum Tube "grids"

[Phil Allison]

"Tim Shoppa"

It is not too uncommon to use tetrodes or pentodes in "triode mode" by
tying the grid and screen together.


** That is completely false and will not work.

In "triode mode" the screen grid is tied to the plate while the suppressor
grid or beam plates are tied to the cathode as usual. The screen grid is
crucial to the operation of a power tube - if tied to the cathode the tube
will barely pass current, if tied to the plate you have a triode. If the
screen supply voltage is insufficient, the tube will not pass full current
and lack gain.

If the screen supply voltage is set too high, it will become the final
destination for far too many electrons and quickly burn out from
overheating.


That doesn't mean the screen grid
is the same as the control grid, in fact in beam power tubes the
screen grid is sometimes better identified as a "beam forming plate".


** Nonsense - see any tube data book for how beam plates are connected
internally to the cathodes of beam tubes, eg;

http://www.pentodepress.com/tubes/6L6.pdf




....... Phil

 

[Eeyore]

FWICT, Jamie is several orders of magnitude ahead of JS when it comes to
"getting it" and acting civil, so I think you're being unfair to him. It
appears that JS is only happy when he hears what he wants to hear. It seems
that everything said that disagrees with his "understanding" or
wishes/fantasies is perceived as some kind of personal attack against his
intelligence.

I won't disagree with that but Jamie says some amazingly cretinous things too.

Graham

 

[Eeyore]

FWICT, Jamie is several orders of magnitude ahead of JS when it comes to
"getting it" and acting civil,

He never acts in remotely any civil way to me. Clearly he's fearful of people
with greater experience and intellect and compensates with hostile responses.

Graham

 

[Adrian Tuddenham]

You guys don't get it. I don't care about the output. It is for an audio
project ...

To call such a project "audio" is like calling astrology "astronomy".
You have a great opportunity to learn something here and, instead, you
appear to think you are doing something worthwhile by wallowing in
semi-ignorance.

For goodness sake start to tackle this project in an adult way and learn
something about it before you waste hours or even years of your life
pissing about with something which has already been well-researched.

If you carry on without knowing what you are doing, your project will be
treated with the contempt it deserves. ...but with a bit of serious
background reading and your interest in the 'artistic' side of audio,
you could gain a good understanding of valve distortion effects which
would serve you well in future.

 

[Eeyore]

To call such a project "audio" is like calling astrology "astronomy".
You have a great opportunity to learn something here and, instead, you
appear to think you are doing something worthwhile by wallowing in
semi-ignorance.

For goodness sake start to tackle this project in an adult way and learn
something about it before you waste hours or even years of your life
pissing about with something which has already been well-researched.

If you carry on without knowing what you are doing, your project will be
treated with the contempt it deserves. ...but with a bit of serious
background reading and your interest in the 'artistic' side of audio,
you could gain a good understanding of valve distortion effects which
would serve you well in future.

Starting by understanding the function of the control, screen and suppressor
grids would be a good start.

Graham

 

[Eeyore]

Another interesting tube type is the 'remote cutoff' or 'variable-mu'
pentode, e.g. the 6BA6, in which the control grid is wound with a
varying pitch. The tightly wound parts cut off before the loosely wound
ones, leading effectively to a modulation of the cathode area with grid
bias. They make pretty good AGC amplifiers, but have poor strong-signal
linearity.

That style of design always fascinated me. It's quite clever despite the defects
you mention.

Graham

 

[[email protected]]

For goodness sake start to tackle this project in an adult way and learn
something about it before you waste hours or even years of your life
pissing about with something which has already been well-researched.

This is Jon Slaughter you're talking about. Tomorrow he'll be asking
about something completely different and ignore you there as well.
Plus he'll never learn the difference between your and you're, and
he'll always be an apostrophe pluralizer...

 

[Eeyore]

This is Jon Slaughter you're talking about. Tomorrow he'll be asking
about something completely different and ignore you there as well.
Plus he'll never learn the difference between your and you're, and
he'll always be an apostrophe pluralizer...

Sadly this is likely all too true. In the UK we often call it the
'greengrocer's apostrophe' btw. As in Apple's, Pear's, Tomatos's etc.

In pubs I've even seen chalked up on the menu board, Fish and Chip's.

For USAans, chips here are what you call fries.

Graham

 

[[email protected]]

Slaughter is what should happen to him. Aside from Jamie, he must be the
dumbest here.

Graham

Nah, you forgot Skybuck Flying ...
Take away the "s" and you're left with LAUGHTER, which is how you
should look at it.

 

[Eeyore]

It depends upon where you order them. Same as in the UK nowadays.

Don't get out much?

Not to the USA. Mainly Asia. North Africa was intersting too as was Scandinavia.
I fancy doing Iceland some time too.

Graham

 

[Rich Grise]

For USAans, chips here are what you call fries.

I saw some travelogue where they showed a fish & chips stand, and it
was big chunks of potatoes (like we'd call "steak fries") and big chunks
of some white fish, served in a cone of newspaper, and incredibly greasy;
If I ever have an opportunity to see England, I'd like to try some. ;-)

(Yes, I like greasy food - Need to keep that ol' cholestrol count up in
the "normal" range so I don't wither away! ;-) )

Cheers!
Rich

 

[Glenn Gundlach]

researched.

This is Jon Slaughter you're talking about. Tomorrow he'll be asking
about something completely different and ignore you there as well.
Plus he'll never learn the difference between your and you're, and
he'll always be an apostrophe pluralizer...

You forgot their, there and they're.

GG

 

[Paul G.]

You guys don't get it. I don't care about the output. It is for an audio
project and and I am looking for different effects I can get which want
those different possibilities. I don't know how many times I have to say it.
I'm only concerned with the circuit topology used to drive the grids as
somehow having to be different or I'll end up fucking up the tube. But now
that I think about it it's quite obvious that the circuit topology can be
the same.

E = -phi_n+1 - sum(grad(phi_k)) - phi_0

where phi_k is the potential of the kth grid, phi_0 is the potential of the
cathode, and phi_n+1 is the potential of the anode.

phi_k might depend on material, temperature, geometry, etc... but since the
ultimate result is the potential(which is basically what I was trying to
ask) it doesn't matter. I just have to put a voltage across it and only make
sure I don't go over the current rating. That means that I'll get some
effect. THE TUBE MIGHT NOT OUTPUT ANYTHING but that is of no concern to me
as I mentioned I will be playing with "ideas". You guys seem to think I'm
going to randomly hook up the grids in some configuration for some
application then run it into mass production. You don't get that I am
simply going to play around with some idea(And it shouldn't matter) and see
what kinda outputs I get.

What is important too me is that I don't blow up the tube because one of hte
grids, say, happen to be created in a way that resonates at some frequency
and when I hook up my circuitry too it I end up hiting that resonance and it
creates an atomic explosion. I've mentioned many times before I'm not
interested in the signal output but the not ruining the components.

so, for you what works it's totally different from me. If I hook up
something to the grid and I don't ruin the tubes then it works... regardless
of the output. I guess this is a very difficult concept for people in this
group to comprehend but I guess then again they never "play around" with
circuit ideas and just copy shit out the book.

In your quest for vaccuum tube weirdness, look into the behaviour
of 6AR8 / 6JH8 / 6ME8 / 7360. These tubes use two electrodes that
steer the current between two adjacent plates. That allows you to
generate balanced modulation and other interesting effects.
Check this site: http://www.cgs.synth.net/tube/beam.html . Eric
Barbour has some interesting audio applications for some of these
strange tubes.
Check out the 6BN6, my old RCA tube manual doesn't say much about
it, but at heart it's a very weird little tube, and it's used for FM
quadrature detection, a neat little trick that was exploited in
probably millions of tube TV sets. Check out:
www.clarisonus.com/Archives/TubeTheory/6BN6_part_1.pdf and
www.clarisonus.com/Archives/TubeTheory/6BN6_part_2.pdf
If you thought tubes were pretty simple, the above articles will
change your mind! They play around with the "space charge".
There's a gold mine of info in the www.clarisonus.com/archives .
There are a number of vendors selling audio special effects boxes that
incorporate the 6BN6.

Paul G.

 

[Rich Grise]

There's a gold mine of info in the www.clarisonus.com/archives .
There are a number of vendors selling audio special effects boxes that
incorporate the 6BN6.

Haven't you figured out that JS doesn't _want_ to know the facts?

Thanks,
Rich

 

[Eeyore]

Nah, you forgot Skybuck Flying ...
Take away the "s" and you're left with LAUGHTER, which is how you
should look at it.

<chuckle> And I thought he'd even made some rational comments recently. (not
Skybuck that is) ;~).

Graham

 

[Eeyore]

I think my next trip will be to India, which is my wife's first choice.
After that, I want to do Greece followed by Ireland.

Where in India ? Be prepared to see some things that may shock, although the
tourist destinations are pretty clear of that stuff.

BIG tip: if you start giving the beggars money you will collect them like flies.

Graham

 

[Eeyore]

I saw some travelogue where they showed a fish & chips stand, and it
was big chunks of potatoes (like we'd call "steak fries") and big chunks
of some white fish, served in a cone of newspaper, and incredibly greasy;
If I ever have an opportunity to see England, I'd like to try some. ;-)

Oh it's not *that* greasy at all. It's cooked in vegetable oil and generally
the oil is allowed to drain well before serving.

It has to be clean new white paper now too.

(Yes, I like greasy food - Need to keep that ol' cholestrol count up in
the "normal" range so I don't wither away! ;-) )

Don't forget the vinegar and salt on the chips.

Graham

 

[rex]

You forgot their, there and they're.

GG

How about the random and interchangable use of then and than. That's the
one that drives me nuts, and from people I wouldn't expect.

If you think their ever going to change there ways than your more
optomistic then me.

Make's me want to go neucular.

 

[rex]

How about the random and interchangable use of then and than. That's the
one that drives me nuts, and from people I wouldn't expect.

If you think their ever going to change there ways than your more
optomistic then me.

Make's me want to go neucular.

I think its the fault of those special interest's and earmark's in
Warshington.

 

[Richard The Dreaded Libertarian]

I think its the fault of those special interest's and earmark's in
Warshington.

It's the fault of the unions and other socialists dumbing-down the
schools.

Vote None of the Above:
http://www.bobbarr2008.com/