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Old 19th June 2008, 03:05 PM   #1
oldeurope is offline oldeurope  Germany
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Default pse help, unity triode as a phase inverter

Hello,
I am searching for a unity triode as a phase inverter.
Something like the triode section of the ECLL800.
At the moment I am using a 6080 ( ≈ 1,5 @ 1mA)
but it is a bit oversized in this application.
Any other suggestions?

thanks,
Darius
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Old 19th June 2008, 10:54 PM   #2
nigelwright7557 is offline nigelwright7557  United Kingdom
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Default Re: pse help, unity triode as a phase inverter

Quote:
Originally posted by oldeurope
Hello,
I am searching for a unity triode as a phase inverter.
Something like the triode section of the ECLL800.
At the moment I am using a 6080 ( ≈ 1,5 @ 1mA)
but it is a bit oversized in this application.
Any other suggestions?

thanks,
Darius

You dont need a unity u valve for a phase splitter.
Just set the anode resistor and cathod resistors to the same value. Same current through both means same voltage but 180 degrees out of phase.
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Old 20th June 2008, 06:29 AM   #3
oldeurope is offline oldeurope  Germany
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Default #2 no fb ...

Quote:
Originally posted by nigelwright7557

You dont need a unity u valve for a phase splitter.
Hello,
I am searching a unity triode as a phase inverter.
Something like the triode section of the ECLL800.

Quote:
Originally posted by nigelwright7557

Just set the anode resistor and cathod resistors to the same value.
No negative feedback please.
Sorry I forgot to point this out.

Kind regards,
Darius
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Old 20th June 2008, 11:17 PM   #4
nigelwright7557 is offline nigelwright7557  United Kingdom
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Default Re: #2 no fb ...

Quote:
Originally posted by oldeurope


Hello,
I am searching a unity triode as a phase inverter.
Something like the triode section of the ECLL800.



No negative feedback please.
Sorry I forgot to point this out.

Kind regards,
Darius

But there is no feedback in my example !
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Old 20th June 2008, 11:23 PM   #5
ray_moth is offline ray_moth  Indonesia
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Quote:
No negative feedback please.
So, Darius, what sort of splitter had you in mind?
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Old 21st June 2008, 07:55 AM   #6
oldeurope is offline oldeurope  Germany
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Default #2 #4 #5

@#2 #4 current feedback.

@#5

Quote:
Originally posted by ray_moth


So, Darius, what sort of splitter had you in mind?
Hello ray_moth,

I am searching for a unity triode as a phase inverter.
Something like the triode section of the ECLL800.

See attachment below.

Kind regards,
Darius
Attached Images
File Type: png phase_inverter.png (8.4 KB, 507 views)
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Old 21st June 2008, 12:39 PM   #7
mashaffer is offline mashaffer  United States
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I think he literally means a phase inverter (i.e. unity gain inverting amplifier) rather than the phase splitter for a PP amp that we generally think of when the term PI is used.

mike
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Old 21st June 2008, 02:08 PM   #8
ray_moth is offline ray_moth  Indonesia
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I see, I wasn't thinking that literally. Well, if there is such a triode, I don't know of it. There's always a 1:1 transformer, of course.
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Old 21st June 2008, 05:36 PM   #9
smoking-amp is offline smoking-amp  United States
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I don't think one will find a Mu = 1 tube since that would require the plate to be as close to the cathode as the grid, or a very open mesh grid, which would be non-linear. Since the Mu factor is a measure of internal feedback anyway, why the avoidance of feedback techniques?

If one "must" get a low Mu, try the voltage mirror scheme used at the input of the Aikido amps. Use of an identical triode as the active load drops the Mu in half by halving Rp. Using more than one active load triode in parallel will get you even lower Mu.

Another approach is to put thermionic diodes in series with the cathode path. This will lower Mu asymtotically toward unity, but will raise output Z.

Another way would be something like the 6ME8 beam deflector tube, with the plate load resistors adjusted to a value that gives unity gain. The voltage swing on the plates will then be exactly countering the effect of the deflection voltage on the deflectors.

Don
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Old 21st June 2008, 06:09 PM   #10
kenpeter is offline kenpeter  United States
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Well, there is always inverted triode. Mu'=1/Mu
Drive the plate negative and take a Mu' output
from forward conduction of the the grid.

Mu*(1/Mu)=1

I dunno how suitable is 6922. Just pulled that
from the air cause it can tolerate the cathodes
being at wildly different voltage. Perhaps 6N30Pi
might have a beefier grid? 6080 is good for invert,
but you wanted something smaller.

Incomplete OT schematic without part values
just the way you like em... I'm sure you could
even find some way to turn this Loftin/White...

I'm not sure which rail you prefer common to
power noise in this situation. Depends what
are you intending to drive in the next stage?

What was the trouble with Mu>1 and a resistive
divider??

---------------------------------------------------------

Nutz... I inverted twice.... Thats not helpful!

If I make the inverted triode behave as a follower
then overall Mu does not revert to 1 as intended.
I don't see an easy way to fix this.
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File Type: gif unitymu.gif (20.2 KB, 404 views)
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