Concertina Parafeed, or How to mess with OldEurope's mind...

[oldeurope]

Originally posted by kenpeter
Completely OT, this should add some "4th circuit" fuel to the fire!

http://www.diyaudio.com/forums/showt...10#post1545510

[kenpeter]

Oh, you liked that one did you?
Now contemplate this if you dare...

We have:

4th Circuit - Differential Fetrons,
Two Common Noises ref'd to B+
"Brute Force" DC current balance.
DVC Sub abused as a self-OPT
H-Bridged Full Ranger.

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

Fetrons differ from triodes mostly
in having a low impedance at the
gate. Having "external-insic" NFB
to defeat intrisic "screeni-ness".

One has to be careful to drive from
a well controlled impedance, as the
ouput of the driver becomes part of
the input mixer/divider to the Fetron.

Same could be said for OHSchade's
1938 triode emulation, abusing beam
power tubes with screens tied high.

The same OTL circuit with slightly
different bias could be done with
a gang of regulator triodes. The
4th circuit "Long Neck(s) Pair"
is the same either way.

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

Gratuitously threw a beam tube in
place of original depletion FET at the
input, to keep it plausibly relevant.
No rule against replacing FETs with
real tubes!

The high plate impedance lets the
load resistor alone set the stable
predictable driving impedance the
Fetron will want/need to see.

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

No component values specified,
just the way we like em! I'd prob
suggest networking a low Mu for
the Fetrons, to keep the swing of
the Drains/Plates from wasting too
much of B+.

Never suggested this circuit was
efficient, nor practical. Only another
half baked excercise in circuit abuse.

Blindness Warning!

[smoking-amp]

Ken,
You must be smoking some pretty strong weeds over there. I take it that "long necked pair" refers to a "plate" connected pair. Now what is DVC and FR? This is looking more like, can I say "normal" without breaking some conventions, P-P now, rather than a Circlotron.

But Fetron tube emulations in both forward and reverse directions, definitely breaking all the usual rules. My guess is that the reverse Fetron is not getting equal gate drive though, unless the resistors are tuned differently. Shouldn't the input tube have some plate feedback too?

What you need is a tube with interleved spiral grids at the same distance from the cathode. Then use one for input, and the other for output. There are some dual control tubes that have two grids and two plates, but are on opposite sides of the cathode. Not sure how well they would share the cathode current. The 7360 beam deflector is probably as close as one can get to this geometry.

Don

[kenpeter]

Normal? No never... Refer to Technical Forum Rules

DVC=Dual Voice Coil, make all that excess overhung
bifilar inductance actually do something (useful?).
FR=Full Range, or whatever passes for full range...

Wasn't going for Circlowhatsitnot or Loftin this time.
Not that I wouldn't go there. Difficult to smoke every
variety of electric mushroom at once and still able to
post. Don't have to explain that to you, now do I?

I chose a high impedance pentode plate for the input,
so not to mess with the voltage divider of the Fetron.
Actually the driver to a Fetron can be any impedance,
so long as it isn't significantly dynamic or reactive...
And the combined bias and local NFB network must
be tweaked to accommodate those changes.

A low impedance follower with a series resistor out is
another stable way to drive a Fetron, but that would
be too normal. I wouldn't get to float on B+ ripple...
Where is the challenge then? I would bypass the
other side's "drive" to ground instead of B+, boring!

Any emulator that won't work in 4th circuit topology
doesn't emulate a Triode in my book. Too many sand
state circuits that claim to act like tubes simply do not
pass any test of realism under dynamic variance of
plate load...

The Long Neck Pair works fine with a single high value
Resistor, CCS, Choke, or Gyrator... I happen to choose
a CCS split in twain, then bridged with a capacitance.

MJK dubbed one my previous split source "Brute Force".
Of course, that was for a much higher value cap to bridge
a Cathode to an AntiTriode's Source. On the difficult low
impedance "Tail" end of an earlier Triode / Anti-Triode
differential pair.

There is no Anti-Triode in this schematic, so stop looking.
There is also no "Tail" except the actual load itself. Look
to the phase dot(s) of the DVC windings. Its wired only
to behave as a common mode short, and a differential
mode load and self-choke....

I think the 4th circuit's "Neck" has high enough impedance
to allow a much more reasonable capacitance in the split
current source bridge. If a forced perfect "brute force" DC
balance is actually needed, and in many cases it is not.

The cap on the FR must bridge the low impedance end of
the pair, but not the lowest notes as handled by the DVC.
Even this cap therefore might be of a reasonable value...

[oldeurope]

Hello Don,

Originally #23 posted by smoking-amp
Ken,
You must be smoking some pretty strong weeds over there.

kenpeter gives us incomplete schematics without values.
And this isn't for the first time here.
Thus his schematics can be interpreted in different ways, of course.
This makes it possible for him to say "you are wrong" etc.
But I didn't say anything in post 21 "Blindness" comes from his mind.
Ken is very annoyed. I don't like to feed him any more.

Kind regards,
Darius

[kenpeter]

Topology brainstorming sessions don't always need specific values.
A lot of these wacky ideas will never go any further. I do attempt
to fit values to an idea when I think there is a need to further test
if it can be biased properly. And have done so even in this thread.

Annoying is when a guy offers to help explain a difficult topology,
and then withdraws that help because you can't teach a mosfet
from Texas to sing a CHB, or whatever sigline was at that time...

If I have to figure it all out for myself, you shouldn't be offended
when I occasionally draw the wrong conclusions, or more often
take your good traditional ideas down an unexpected tangent...

I don't like when your posts are missing the