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Chris Hornbeck Chris Hornbeck is offline
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Default Explanation still required for triode superiority

On Tue, 26 Sep 2006 10:01:18 +0100, Eeyore
wrote:

It's a subject that truly intruiges me.

Where I suspect I'd differ with you is that I'd expect a DSP simulation to
sound just the same as the beloved triode.

It is something that I'm looking into btw.


Could we begin by agreeing that a simulation is at least
*possible*, including *all* possible issues, including
non-linearities in time and amplitude, and at all levels;

and will happen, for reproduction (not real time) soon.

Slightly, a few orders of magnitude, no biggie, of
horsepower will extend this to close-enough-to-real
time for performance. Again, soon... ish.


The first step to that goal is right here, right now,
to define the actual things that need to be captured.

There are *real* things to be captured, not fantasies.
And I'd suggest that it's a worthwhile and potentially
interesting target.

Much thanks, as always,

Chris Hornbeck
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Chris Hornbeck Chris Hornbeck is offline
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Default Explanation still required for triode superiority

On Wed, 27 Sep 2006 02:44:56 GMT, Chris Hornbeck
wrote:

Could we begin by agreeing that a simulation is at least
*possible*, including *all* possible issues, including
non-linearities in time and amplitude, and at all levels;


Should add that I don't actually know if this can be done.
Randy Yates seemed to feel quite differently about a
related issue, and I don't have the mental horsepower
to dispute his opinion.

But, maybe as a talking point...

Much thanks,

Chris Hornbeck
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Eeyore Eeyore is offline
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Default Explanation still required for triode superiority



Chris Hornbeck wrote:

On Tue, 26 Sep 2006 10:01:18 +0100, Eeyore wrote:

It's a subject that truly intruiges me.

Where I suspect I'd differ with you is that I'd expect a DSP simulation to
sound just the same as the beloved triode.

It is something that I'm looking into btw.


Could we begin by agreeing that a simulation is at least
*possible*,


Very much so I think.


including *all* possible issues, including
non-linearities in time and amplitude, and at all levels;


I don't see where time comes into it actually. Do feel free to comment on this
point.


and will happen, for reproduction (not real time) soon.


What do you mean by not real time ? I'm entirely sure it's possible to simulate
in real time. Modern inexpensive DSPs offer ~ 100MIPS. Using say 96kHz sampling
that allows ~ 1000 instructions per sample period which I'm sure will suffice.


Slightly, a few orders of magnitude, no biggie, of
horsepower will extend this to close-enough-to-real
time for performance. Again, soon... ish.

The first step to that goal is right here, right now,
to define the actual things that need to be captured.


Yes, I'd agree there. I'm still considering the best way to approach the
'modelling' required. There's a few ways of doing it.


There are *real* things to be captured, not fantasies.
And I'd suggest that it's a worthwhile and potentially
interesting target.


It certainly has my interest.

Graham

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Chris Hornbeck Chris Hornbeck is offline
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Default Explanation still required for triode superiority

On 26 Sep 2006 15:30:25 -0700, "Andre Jute" wrote:

3. We make totally unwarranted assumptions of monotonicity.
This is a fatal flaw in our thinking, and we all do it, all
the time.

4. We make often unwarranted assumptions about input signal
bandwidth.

5. We *always* *without exception* forget to properly weight
the importance of simply being upstream in the signal path.
Always.


elaborate on points 3, 4 and 5.


We're always fighting the last war. In my on-war-footing and yet
war-unravaged country, this seems particularly unwise, but
still unavoidable.

Progress in any sufficiently mature technology is less a matter
of perfecting the existing technology than in identifying the
flaws in the model by which the technology was created.

Any second rate modern military power could have ruled the world
of even only a hundred years ago. And, conversely, the Number One
Military Might Big Kahuna in the contemporary world can't defeat
a determined insurgency in a militarily defeated and occupied
country. (Or two).

Defining the problem is everything. Defining the problem in the
context of the last war is foolish, but seemingly unavoidable.
Failure to recognize this trap is potentially fatal militarily,
and a blind alley technically.


Which conclusion? That "triodes sound better" or that "there must be an
electrical explanation"?


strong disagreement ('cause
that ain't science!) with the latter.


Eh? Surely a thermionic valve is nothing but a bunch of electrical
impulses created by vacuum, wire and electricity? Whatever happens in
there, regardless of whether we can see it or not, regardless of what
we call the result, *must* perforce have an *electrical* explanation.
°That* is science. Anything else would make me uncomfortable -- and me
a certified witchdoctor!


Gotta be more careful with my phraseology. It really depends on
what "be" be. Arf!

Have I heard a technically compelling explanation for ..some.. of
the things that I nonetheless believe to be both true and ultimately
explainable to me in terms that I can accept as real? No.

Do I believe that explanations acceptable to me exist and are
awaiting discovery? Yes.

Science is the quest(ion) itself, so we really aren't in disagreement.
And, I'll try to work up some more keystrokes about my favorite
bete noirs, monotonicity and operating level later, 'gator.

Much thanks, as always,

Chris Hornbeck
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Patrick Turner Patrick Turner is offline
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Default Explanation still required for triode superiority



Somebody said, and Andre replied.....



Modeling and analysis are essential; but the map is not
the world.


Actually, the only °essential* is having some method of deciding where
you want to arrive. High fidelity went wrong long before Mr Leak's
inspired marketing terminology (Point One) became an engineering
article of faith, but that set the seal on the decline.


So what happened before Leak that was the beginning of the fidelity decline?
Invention of pentodes and bean tetrodes? Beginning of FB use?
Indirect heating of cathodes?


Patrick Turner.



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Andre Jute Andre Jute is offline
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Default Explanation still required for triode superiority


Phil wrote:
Andre Jute wrote:

I've read your arguments, Phil. Their subtext is methods to make NFB
more usable, less damaging to reproduced sound. That is a legitimate
outlook for Otala, who has to fit into an existing industrial
environment where NFB is an ineradicable part of that dominant
electronics cost-accounting system in which the explicit purpose of NFB
is to make cheap parts tolerable.

But that has buggerall to do with me as a DIYer. I can afford to take
the far simpler, more fundamental course of making my amps so superior
in design and components right from the start -- that I can do without
NFB and without the damage that NFB does. So I design amps without NFB,
period. I shortcut the problem of NFB and eliminate it before it
arises. My amps are ultra-silent without NFB; they do not need NFB for
any purpose whatsoever. Since one of my ZNFB amps is capable of 80W
when in its PSE mode, more than enough to drive electrostatic panels to
power-rivetter volume, I take the view that any designer who requires
NFB to make his hi-fi amps work has either permitted cost-accountants
to bully him, is an impressionable fashion victim, or is too thick to
put his mind in gear, tick one or more boxes.

The rest is interesting speculation but not of such consuming interest
to me that I will spend a morning setting up bench experiments to prove
the details of something I already know: that NFB smears the sound. A
complete summary of my view on NFB can be found here
http://members.lycos.co.uk/fiultra/K...dre%20Jute.htm
and here
http://members.lycos.co.uk/fiultra/K...dre%20Jute.htm

I haven't changed my mind one jot or tittle over the recent discussion.
I have heard absolutely nothing that proves a contrary case. That is
not to say you may not be right, that the psycho-acoustic effect which
gives Class A1 ZNFB (or very low NFB) amps their distinct superiority
is a subliminal reaction to the HF phase- smearing in NFB amps that you
say Otala posits. I just haven't seen any proof yet, and know that,
when I do see such proof, I will consider it of intellectual interest
-- and continue to build the sort of ZNFB amps I have always built, in
which NFB is excluded for its amplitude smearing at frequencies
starting below 100c/s, so that HF phase smearing, if it exists in NFB
tube amps, is no danger to my sound.


Be fair now, you didn't ask, "Why should I build high feedback pentode
amps,"


But I do build pentode amps, if without the "high feedback". The best
amp I ever designed, my Type 114 "Triple Threat" is a PP EL34 with a
pentode/ultralinear/triode switch and NFB tunable from zero to about
6dB in the latest iteration but up to 20dB in some early versions. Of
course, it is my "best" amp only when operated in the trioded ZNFB
mode, but the choice is in the hands of the builder.

you asked, "Why do do [no feedback] triode amps sound better?" I
merely attempted to give you an answer. You believe that triodes have an
internal feedback mechanism, and you wondered why they (still) sound
better.


My point is a little more subtle. I see an effect which looks like NFB
happening between the terminals of a triode; I'm happy to call it
internal or natural NFB until someone else offers an explanation that
justifies giving it another name; no one offers such an explanation,
merely negative objections to naming it NFB; until they pull their
finger from their arse and say something positive (and more cogent)
than Patrick, who *does* have a case, I shall not change my mind just
because they're "agin". You should also understand that some of these
clowns are agin not for any good reason but only because it is *me*
saying so; Pasternack, for instance, and the usual sockpuppets of the
Magnequest Scum, whose disruptive presence on RAT I dispensed with
wholesale a few years ago ("Jute is wrong even if he is right, isn't
he?" one of them, Ron Bales, complained pitifully!). Pasternack, for
instance, has been repeatedly caught out lying on professional matters
"in my zeal to flame Andre" -- which is his own sickening excuse in his
own words.

The basic core of my response/answer is that (1) negative
feedback transforms relatively benign amplitude distortion into much
less musical phase distortion, and (2) either triodes do *not* have this
distortion mechanism, or it occurs at such staggeringly high frequencies
that triodes can "get away with it," since the amount of phase
distortion produced decreases as the high frequency limit increases.


I don't need to go that sophisticated. By far the most popular of my
loudspeaker designs (of the published ones; an expensive licensed speak
sells amazingly well in the Far East considering the wretchedly high
price dictated by the cost of the drivers) is an economy fullranger
using a guitar driver, in most installations that I know of with the
tweeter disconnected or, on my advice, never fitted.
http://members.lycos.co.uk/fiultra/K...Impresario.jpg
It has been years since I have been impressed with bandwidth as measure
of audio goodness, and I don't just mean excessive bandwidth, I mean
the upper end of what is commonly called the "audio spectrum". Most
people can't hear it even when they're young. Most people into hi-fi
are over middle age; they're lucky if they can hear past 12kHz. In any
event, Top C on a piano is a frequency of 4186c/s; over 70% of the
energy of that note (over half the decibel value referred to the
fundamental's energy) will be in the 2nd and 3rd harmonics, which takes
you just past 12kHz. (Try an experiment: filter out everything below
the 3rd harmonic of top C, 12558c/s, and listen to what remains. It is
horrid, just white noise.) By the way, the same argument of harmonic
weight in the production of sound applies to the bass end and well into
the midbass: an open G string on a violin played with medium intensity
has only 0.1 per cent of its energy in the fundamental -- which is
196c/s; this is the basis for my thesis that the human ear
reconstitutes the fundamental from the dominant harmonics, where the
energy is. The upshot is that the lower extension of the so-called
"audio range" is another engineering chimera that has nothing
whatsoever to do with music and everything to do with a bunch of
arrogant engineers sitting in a room feeding of each other's
testosterone while setting standards that should instead have been set
by psychologists or musicologists or, in fact, anyone but engineers. In
practice, it means that you can roll speakers off quite high, where the
bass will "measure" modestly but sound very, very clean, and they will
sound better over the long term than those one-note boof-boff big-bass
abominations so beloved of "audiophiles" and "engineers" alike. Peter
Walker didn't build his ESL63 any bigger than 45c/s bass (the last pair
I measured was 8dB down at 32c/s) because to the ear even a 16c/s organ
note, if on the recording at all, will sound startlingly precise
because all the energy are in the first two harmonics above the
fundamental.

More, drivers with a natural high frequency mechanism, like the classic
Lowther driver, can sound screechy in the treble precisely because it
is not a fundamentally natural noise
http://members.lycos.co.uk/fiultra/K...20T91HWAF3.jpg
Lowthers with the whizzer tweaked by the insertion of cotton wool
behind it or by stiffening with C37, always sound more "natural" even
as the measurements start looking less impressive. (I prefer the
waterfall anyway, but only after I have run it through a smoothing
program because the small glitches are a distraction to the eye but not
the ear.)

And I proposed a test, which may not work anyway, and which apparently
only I have any interest in performing! However, I believe you when you
say you already know that feedback smears the sound somehow, and don't
need a test to "justify" your decisions, which is a stand I do respect.


Hang on a minute. I have demonstrated smearing in the frequency band
I'm interested in. I've done it again and again and again,
theoretically by mathematics, by measurement with instruments,
graphically, and by placebo listening tests (what the pretentious call
ABX).
http://members.lycos.co.uk/fiultra/K...dre%20Jute.htm
http://members.lycos.co.uk/fiultra/K...dre%20Jute.htm
I have no problem standing by my taste when taste is the question (for
about ten years I was the most widely read music critic in the world
with a column syndicated to 9.2m readers every week) but when science
has an answer I am as keen as the next man (and clearly keener than the
diplomaed quarterwits on RAT) to find the correct answer by the proper
scientific method.

For a while there, all of us had to face serious criticisms for saying
that in our own experience, cables do sound different,


Sure, I believe you can hear cables, under two very specific
conditions. Again, my conclusion is based on a scientific test. I flew
to a different country and in a warehouse spliced huge reels of cable
until I had the several of different construction of a length that an
engineer (a proper one, not one of the local clowns) calculated for me
should be audible by the laws of physics. They were, barely. The other
condition under which cables are audible also answers to the laws of
physics: when components in the audio chain are mismatched, the
resistance and capacitance on a particular cable can make the
combination sound better or worse, hence "cable is audible". I
personally use Cardas golden section multi-diameter cable because the
concept appeals to me: my Impresario speak is designed on Phi, the
formulaic base of the golden section.
http://members.lycos.co.uk/fiultra/K...Impresario.jpg

and it really is
a mark of character to stand up and say something that is true, but
"officially" stupid.


Man, you got enough problems already. You really don't want my
character as well: I was sent into exile from my motherland for saying
the statistical basis of apartheid was flawed (everyone could see it
only twenty years after I said it), and later twice hunted by assassins
sent by the apartheid government for a couple of my books.
http://members.lycos.co.uk/fiultra/THE%20WRITER'S%20HOUSE.html
As an economist I was academically haunted by being the only monetarist
in keynesian countries in a keynesian age, as a psychologist in a
Freudian age thought very odd, most unreliable, a loose cannon on deck
for saying that Freud was a literary giant but didn't know **** about
human character. Today, of course, everyone knows I am right and was
right then. That was nothing to the filth heaped on me for saying the
Common Agricultural Policy of the European Community was a wasteful
abomination, or pointing out that the case against DDT was and is
unproven, or that "global warming" is an official lie (I've been saying
it since the 1960s when I had a running joke in a satarical newspaper
column about the missing hole in the ozone layer).

If only the "official" beliefs didn't so often turn
out to be the ones that are actually stupid, we could all be mindless
sheep, and be better off for it! ;-)


Nah, I like being "the most dangerous class", as Lenin called
reformers. Sure, the price has been high, but the alternative would
have been dull.

However, there are sometimes good reasons for more fully understanding
something. If we assume for a moment that my analysis -- which is
basically my attempt to guess at the rest of what Otala was saying,
since I have yet to see the full text -- is correct, then several
interesting things follow. First, since a threshold below which we
cannot hear phase distortion realistically *must* exist


There is no *must* about any threshhold. We're discussing the known
preference for Class A1 triode sound by an important niche of
knowledgeable audiophiles -- despite the known fact that it measures
worse than the alternatives on quite a few parameters. Even if those
parameters are at present driven to ludicrous lengths by the engineers,
it is clear that the highest level of triodes -- DHT, ZNFB, SE or Class
A1 trioded ZNFB PP pentodes -- will never come within a magnitude of
current technology, at least not on the meter. The preference must be
explained by some subliminal effect. The problem with subliminal
effects is that they recede with experience, that is, that they're
educable; for instance, the limit at which distortion now becomes
audible is lower than it was when Olsen first studied the subject 70
years ago.

-- and again,
for Patrick's benefit, this is phase-smearing, and *not* the simple
phase shifting which feedback does correct -- we should be able to add
some feedback and get "all gain, no pain."


You're still on someone else's agenda, trying to make NFB usable. My
amps started sounding brilliant the day I rejected NFB on principle.

Patrick said that he added 6
dB to lower output Z, and it sounded fantastic, as opposed to a 20 dB
version of the same amp.


Hang on a minute. Patrick said that he found that 6dB of NFB didn't
degrade the sound audibly -- a matter of taste for him and his client
which we must permit them to enjoy in peace; I shall just say I tend to
believe that 6dB is very likely a common audibility limit. Patrick also
made the point that the NFB lowers the output impedance, on which he
puts a high priority *because he builds amps for sale, often to be used
with unknown speakers". Anyone who can design his speakers first can
also design them so that output impedance and the consequent need for
NFB is less; amps can be designed to be speaker-friendly without NFB as
long as you know from the beginning that NFB will be excluded.

Well, maybe this is completely true, but if we
*know* that it is true, then, for example, amps that use high-mu
transmitter tubes with positive grid drive and a bit of feedback to get
the Zout down begin to make sense,


Been there, done that. You're still on someone else's agenda, this time
"mo' powa' is betta powa'". It's bullcrap. Even at the lower end of the
same argument, a 211 doesn't sound nearly as good as an 845 when both
are built to give the same power, simply because the 211 must be driven
across the 0V bias line into A2 while the 845 stays strictly in A1.
It's another example of a subliminal effect on the ear when very little
difference shows on the measuring instrument.

especially when the feedback is used
in a two-stage configuration that does not include the output
transformer, meaning that it can have a *very* high upper frequency
limit (you don't need to "dumb down" a stage like you often need to do
with a three-stage to prevent oscillation), which limits the damage
feedback can do to sub-threshold levels. Many people report that they
LOVE the sound of these things, but an unjustified, in this case, bias
against *any* use of feedback could prevent us from even trying one.


No. This isn't a bias against NFB. This is a preference for staying in
Class A1.

Or, let's look at the home builder who wants to make a solid state amp
-- what the hell -- or at least one with a SS output stage.


Sander swears by his hybrid amps. I play SS amps often; the one I like
best is the Quad 405 Mk II, because it is so livable. You might check
Google for the threads when Stewart Pinkerton, a Poopie Stevenson type
clown but with a smidgin more class, challenged me to a design contest.
In theory he was supposed to design a silicon amp to beat my 300B SE
amp, or at least produce something that sounded close to it.
http://members.lycos.co.uk/fiultra/T...trafi-crct.jpg
http://members.lycos.co.uk/fiultra/T44bis-'Populaire'-crct.jpg
Even with months of help and coaching from John Byrns and Patrick
Turner, what Pinko produced was such a botch that not even he wanted to
build it. Bored with waiting for the interminable process to run its
fractious course, I designed my own simple SS amp and showed how it
could be developed to sound something like a good tube amp by driving
it into class A. I'm playing it right now. Thanks for reminding me to
plug it in and try it again; for the cost it can't be beat!
http://members.lycos.co.uk/fiultra/K...dre%20Jute.htm
http://members.lycos.co.uk/fiultra/K...dre%20Jute.htm
http://members.lycos.co.uk/fiultra/K...20mGBschem.jpg
http://members.lycos.co.uk/fiultra/K...%20mGBmatr.jpg
http://members.lycos.co.uk/fiultra/K...%20NoBleed.jpg

Basically, I'm saying that, if there is phase-smearing as you claim, I
also think you're right, that it will be inaudible. I am more
interested in what is audible, even if only subliminally. The rest is
of theoretical interest and my time is limited. Thanks for the
entertainment.

Andre Jute
More at http://members.lycos.co.uk/fiultra/JUTE%20ON%20AMPS.htm
and http://members.lycos.co.uk/fiultra/T...mp%20INDEX.htm

There are
basically two forms of feedback, the normal one, and the "active-error"
version described by J. R. MacDonald and others. The active-error
version only "corrects" the output when an actual error exists, whereas
the standard version has to correct the open-loop gain even when the
load is a steady resistance and the devices are behaving with perfect
linearity. If tests show more phase-smearing with the standard version
than with the active-error version, well, I know which version I would
want to use, or have in a new television. As a bit of a side note, with
better sounding SS output stages, maybe we can more easily hear the
advantage, assuming one exists, of using a tube to produce the error
signal (a tube doesn't have poor quality parasitic capacitances to
potentially mess up the low level information).

All of this may sound like something only of interest to home builders,
but at least some manufacturers actually would be happy to produce
noticeably better sounding products, if they could do so for about the
same money! If EE's in general become aware of the full characteristics
of feedback -- and if home builders start to do this, many EE's and high
end manufacturers will indeed follow, eventually -- then we might
actually see better products in cars and TV's. No, I'm not saying do
this so that we will get better products, but a good understanding of
what is needed to make better audio products does tend to help everyone,
sooner or later. Low output Z triodes are in fact the theoretically best
audio devices at this time, sound-wise, but they require an expensive,
heavy, big, high quality output transformer, and that will always limit
their use.

Or, maybe someone just wants to write an article for AudioXpress about
the true nature of feedback, and how to best use it, if its use cannot
be avoided!

Phil


Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

Phil wrote:

Andre Jute wrote:


In an effort to be agreeable, I tried hard to give you negative
feedback inside the tube as an explanation of the overwhelming
superiority of triodes (or trioded pentodes) for audio reproduction,
among other reasons because NFB is accessible to many who belong on RAT
and is a genetic deformity of the silicon scum whose only purpose on
RAT is dissension. NFB is what the silicon slime abuse to make their
inadequate components sound passable, and what even tubies inspired by
the age of sophisters and cost-accountants use to linearize pentodes.
NFB thus has a base level of familiarity which gives it a head start in
any black box model intended to explain something to diplomaed
quarterwits among the silicon slime as well as the better-educated
kibbitzers in my own camp.

But fine, you want to reject my explanation, then you must offer a
better reason to explain why triodes are such superior amplification
devices to anything else, so much more pleasing to the ear, so much
more accurate to the cultivated taste.

Despite my cracks about the metaphysics of tubes, there *has* to be an
electrical reason for the superiority of triodes. But sure, all kinds
of input is welcome.

Andre Jute


Andre, I think you are too quick to dismiss the idea that feedback
transforms amplitude distortions into phase-smearing, like Otala claimed
in his talk/paper (assuming a paper ever followed the talk!). When
Patrick was defending feedback, he mentioned that poorly designed amps
sound like crap when they have lots of feedback, but that if you fix
them up a bit, meaning get rid of much of their excessive nonlinearities
-- read, *amplitude* nonlinearities -- then adding feedback sounds okay.
Now, if we eliminate the idea that feedback produces random noise -- and
we *know* that it reduces amplitude non-linearities -- then the only
distortion mechanism left, I believe, is phase-shifting. However, I want
to describe the usual "constant 20 degrees phase lag at 40 KHz" as
"phase-shifting," and a dynamic, microsecond to microsecond shifting
back and forth of one frequency relative to another as "phase-smearing,"
or "time-smearing."

What Otala was saying is that applying feedback to circuits with lots of
open-loop distortions, which are (I believe) almost always amplitude
distortions, converts these distortions into a back and forth smearing
of the high frequencies relative to the low frequencies (and it may
smear both in terms of the delay through the amp). Nor can we assume
that this time-smearing is a simple function of the low frequency
amplitude, because it is probably proportional to the magnitude of the
distortions, as well as the LF amplitude: VERY non-musical. When enough
feedback is applied to badly designed amps, the amplitude distortions
become quite small, so why did Patrick find that they sounded much worse
than the same amp sounds when touched up enough to reduce the larger
open-loop amplitude distortions? As you say, *something* is wrong, and
if it isn't high amplitude distortions (it can't be), and if feedback
doesn't produce spurious noises, then the only thing left is exactly
what Otala said, time-smearing.

In essence, feedback *connects* two things that are normally separate in
an amp, namely amplitude distortions, and phase-smearing. It achieves a
balance between these two, a balance which is determined by the speed of
the amp, the amount of feedback, and the amount of amplitude distortion.
Contrary to what you say, Otala was *not* referring to TIM, and
transistors did not become so much faster after 1980 than the ones used
in his '73 article to make the problem he described go away. Yes, the
amps had to be designed well enough to avoid TIM, but that was not a
real problem even in '73 *if* you knew what you were doing. The problem
he described in '80 was quite different, and even high MHz tubes are
subject to it.

The interesting things, assuming that feedback problems are indeed
time-smearing (regardless of whether this comes from the conversion of
amplitude distortions), are one, a single tone will reveal nothing of
this, giving very low THD numbers, and two, multiple tones should show
something, although looking at it in the amplitude realm will only show
higher than expected IMD. There should be a fairly easy way to test to
see if this really produces time-smearing. In general, we put a 4 volt
60 Hz signal and a 10 mV 20 KHz signal into an amp with lots of
feedback, preferably using non-linear sections of the amplifying devices
(say, use two 12AX7 type triodes where the plate curves vary from widely
spaced to closely spaced, and use about 60 to 80 dB of feedback to get
the overall gain down to 1). Use a high pass filter to see only the 20
KHz signal, and use the 20 KHz signal from the generator to trigger the
'scope. If time-smearing exists, then the 20 KHz signal will appear
"fuzzy" on the scope, since it is being shifted back and forth. Repeat
without the 60 Hz signal to make sure the time-smearing isn't coming
from somewhere else, and then also divide the output from each tube down
so that you get the same amplitude output *without* using feedback, and
see if the time-smearing goes away. Finally, if possible test over a
region where the curves are fairly linear, to see if that also reduces
the time-smearing. If so, you have proof that feedback transformed the
amplitude distortion into time-smearing. I will try to do this, but I
have little time, less energy, and not the best test bench in the world,
so it may be a while! If you or someone else both can and wants to try
this, I suspect we will get an answer much faster than if I do it. Note
that we can use pentodes or transistors, too, but using solid state has
the disadvantage of possibly introducing other complications due to the
poor quality silicon parasitic capacitances. Also, I am suggesting the
use of very different magnitudes as well as frequencies for the two
signals, in case equal magnitudes somehow avoids this problem, or at
least masks it from this test. And again, contrary to what Patrick said,
the idea that *if* this were true, then by now someone would have
already tries it, and the results would have become widely know, is just
naive. The human race simply isn't that intelligent, at least not yet.

An interesting conclusion, assuming this feedback time-smear mechanism
exists, is that the output of a feedback amp does *not* match the input
when multiple signals exist! However, our normal tests cannot see this,
since they tend to focus on one frequency at a time. I believe that
Patrick, as well as Otala, said that using local feedback to achieve
good open loop linearity, combined with some global feedback, tends to
sound pretty good. This makes sense for two reasons, first because
although the local feedback will produce phase-smearing, it does so at
*very* high speed, which I believe directly reduces the amount of
smearing (common sense says that as the speed of devices approaches
infinity, feedback becomes "perfect"). Second, the result does contain
some mis-match between input and output, even given the high speed of
local feedback, but now the global feedback will not only reduce the
remaining "normal" amplitude distortions, it should also reduce the
time-smearing produced by the local feedback, since this time-smearing
will still produce an error signal for the global feedback. Of course,
this reduction in time-smearing will itself produce more time-smearing,
but it should be a case of 0.1 x 0.1 = 0.01, so the final degree of
time-smearing is reduced by "dividing up" the total feedback into local
plus global.

Finally, you saw the review of Otala that Phil Allison gave, and I think
you were as impressed by it as I was (although it looked bad to PA).
When a man who was as talented, knowledgeable, and honest as Otala
produces a PROOF that negative feedback *always* transforms the
amplitude distortions of the open loop into phase smears of the closed
loop, we should not dismiss it as simply a problem of "old devices," a
problem that a slight increase in speed can make go away, especially
when the discussion that led to his analysis (the Audio Critic BS
session) included a lot of talk about vacuum tubes, and how their speed
advantage made it easier to use them with feedback. We really should do
at least one or two tests before dismissing his conclusions. Again, I
will try to do so, but if you want to know anytime soon, you should
probably rely on someone else.

Phil




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Andre Jute Andre Jute is offline
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Default The day the worm started gnawing HI-Fi was Explanation still required for triode superiority


Patrick Turner wrote:


Somebody said, and Andre replied.....

Modeling and analysis are essential; but the map is not
the world.


Actually, the only °essential* is having some method of deciding where
you want to arrive. High fidelity went wrong long before Mr Leak's
inspired marketing terminology (Point One) became an engineering
article of faith, but that set the seal on the decline.

So what happened before Leak that was the beginning of the fidelity decline?
Invention of pentodes and bean tetrodes? Beginning of FB use?
Indirect heating of cathodes?

Patrick Turner.


Pick any of those, Patrick, or of these: the start of the search for
power, speakers becoming more insensitive, gramophone records becoming
cheap enough to be everyday items for everyman with the consequent
proliferarion of cheap gramophone consoles, and no doubt a long, long
list of other factors someone may wish to add.

Or, if you're into icon-smashing, choose the day Theo Williamson showed
the world how to use NFB competently to get a *lot* of power without
paying the electrical price, Hafler and Keroes on their finest day
(this is again about power and NFB), CFB from Walker and Williamson
(again, about more power for less cost). It is all a matter of where
you're looking from. You might, for instance, consider the Williamson
and then the Quad II as the zenith of hi-fi, with a long cheapening
decline into silicon; it is an equally valid view (and depends, always,
on which speakers you have in mind to use with their amps...).

In general, these men were driven by external events in a marketplace,
and it is in the external events we must seek our answer.

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

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Bob H. Bob H. is offline
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Default Explanation still required for triode superiority

What's nice about the colt is that it's relatively hard to just pull
the trigger without a clip. Kid - wise, that is. Of course a safe or
lock is the best prevention, but
with the Colt without a clip:
first, the clip has to be located and insterted. Not too hard.
then a round has to be chambered by physically pulling the slide back
with one hand. The weapon can't be pushed into the ground to pull the
slide back. Extremely hard for young hands. Teenagers are another
story, of course.
Then a handgrip safety must be depressed before the trigger unlocks,
made for a grown hand.
To an experienced shooter, all these things are second nature and can
be done within a second.

A revolver can be fired by anyone just by pulling the trigger.

Another nice thing about the semi-auto is that if you can't find the
clip, it's hard for someone else to see that there's no ammo in it ; )




Stuart Krivis wrote:
On Wed, 27 Sep 2006 02:20:39 GMT, Chris Hornbeck
wrote:

personal confrontations is simply the size of the bore;
anybody who's ever looked at the receiving end of a
pistole seems to remember (and mentally inflate) the bore.


Revolvers are even better at this because they also show all the
bullets aimed at you.


And, worst case, ya still gotta knock the ****er down
enough to allow ya to do some serious kicking. Real
people don't just lay down and play dead like in the
movies.


Yes, it's all about plumbing. You have to put as large and as many
holes in the OP's plumbing as you can so that they fall down and stay
down. :-)


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Default Explanation still required for triode superiority

On Wed, 27 Sep 2006 04:53:47 +0100, Eeyore
wrote:

including *all* possible issues, including
non-linearities in time and amplitude, and at all levels;


I don't see where time comes into it actually. Do feel free to comment on this
point.


I should have said something more like "relative timing errors",
variations in group delay between input and output.

Personally, I consider these to be simply time non-linearities,
because the mechanisms that interest me are either modulation,
or things that map as modulation, including the modulation's
IM products.


and will happen, for reproduction (not real time) soon.


What do you mean by not real time ?


Reproduction is inherently "not real time", so processing
time (well, less than a week might be nice) is unimportant.

Performance is affected by processing time ("latency",
as they say nowadays) beyond some threshold. Just a
matter of horsepower and Moore's Law, natch.

Much thanks, as always,

Chris Hornbeck
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Eeyore Eeyore is offline
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Default Explanation still required for triode superiority



Chris Hornbeck wrote:

On Wed, 27 Sep 2006 04:53:47 +0100, Eeyore wrote:

including *all* possible issues, including
non-linearities in time and amplitude, and at all levels;


I don't see where time comes into it actually. Do feel free to comment on this
point.


I should have said something more like "relative timing errors",
variations in group delay between input and output.


In a tube amp, any group delay variation will likely simply be the result of the
output transfomer !

In a s-s amp any variation will simply be minute.


Personally, I consider these to be simply time non-linearities,
because the mechanisms that interest me are either modulation,
or things that map as modulation, including the modulation's
IM products.


It is actually a linear mechanism behind it though.


and will happen, for reproduction (not real time) soon.


What do you mean by not real time ?


Reproduction is inherently "not real time", so processing
time (well, less than a week might be nice) is unimportant.

Performance is affected by processing time ("latency",
as they say nowadays) beyond some threshold. Just a
matter of horsepower and Moore's Law, natch.


'Real time' DSP processing is quite easy these days. It may involve a few ms of
delay but not much more.

Graham



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Andre Jute wrote:

Patrick Turner wrote:


Somebody said, and Andre replied.....

Modeling and analysis are essential; but the map is not
the world.

Actually, the only °essential* is having some method of deciding where
you want to arrive. High fidelity went wrong long before Mr Leak's
inspired marketing terminology (Point One) became an engineering
article of faith, but that set the seal on the decline.

So what happened before Leak that was the beginning of the fidelity decline?
Invention of pentodes and bean tetrodes? Beginning of FB use?
Indirect heating of cathodes?

Patrick Turner.


Pick any of those, Patrick, or of these: the start of the search for
power, speakers becoming more insensitive, gramophone records becoming
cheap enough to be everyday items for everyman with the consequent
proliferarion of cheap gramophone consoles, and no doubt a long, long
list of other factors someone may wish to add.


If we ignore history, we make a grave mistake.

I cannot see that there was ever a period where suddenly hi-fi was established in
say about
1930 where we had low thd, good bw, high DF, good SNR, and all without NFB
and just a reliance on DHT triodes.
Just about every single link in the recording industry as existed before vinyl was

pretty damn awful and required listeners to have a few drinks before they could
fully
ignore the noise & distortions on shellac 78s.
Microphones and speakers, including horn types and the calibration of
the measurement systems for such items were all rather attrocious.
There definately was a need for a tone control in 1935.
Either that or an axe, and nobody I ever heard of
used a graphic equaliser to flatten the routinely no flat response in just about
all attempts to record and replay anything.


With amps, the search for power led to a 300B in around 1928 and it was
a large improvement on using a pair of 2A3
to get about the same power, although a pair of 2A3 can do 8 watts.

The invention of the KT66/6L6 type of tubes meant
more folks could have 8 watts with less Pda, but with a lot mote THD
and attrociously high DF, so NFB was a must to at least
to pull the Rout down to the triode level without loop NFB.
Because NFB was something that hardly anyone understood except the
boffins in white coats then it couln't much be used because of the ignorance about

gain and phase shift.
The official % of folks who understand NFB application remains extremely low.
Williamson officially defined ways and means to be able to use
20dB of NFB and get away with it without clouds of smoke.
Its an arguable point as to whether well applied loop NFB ruins a triode
amplifier's
sonic performance or not.
The jury has been out on this and for the verdict on multigrid guilt since about
1935, no?



Or, if you're into icon-smashing, choose the day Theo Williamson showed
the world how to use NFB competently to get a *lot* of power without
paying the electrical price, Hafler and Keroes on their finest day
(this is again about power and NFB), CFB from Walker and Williamson
(again, about more power for less cost).


Well, the Williamson 16 watt amp didn't depend on its power from two triodes
because there was loop FB added.
Williamson merely made the power that was available from a pair
of class A trioded KT66 into power that was virtually entirely free
of any contributing distortion in any audio amp applications.
All the other things in the audio chain of 1947 contributed far
more grunge to any listening experience than that contributed by
the ideas of Mr W.
The W amp was a start to cleaning up what was a dirty act; the act of
recording something so that replay could not be distinguished from the live
performance.
He showed what could be done, and engineers have worked ever since to improve the
measurements.
After having put several zeros in front of the 0.1% thd at 16 watts
to get say 0.0001% at 200W, ( Halcro ) exactly what has been achieved?
Not much, imho, in amplifiers.
Most improvements to audio we experience seem to have occurred
in areas elsewhere to that of amplifiers.
The modern speaker is, imho, a damn sight better than anything from1947,
even though its is more insensitive; seems like a flat response without
cone resonance and cone breakup is more readily achieved
with the modern approach.
Then Walker stepped in with something to bomb everyone, the ESL57.

But now we have had clean sources from master tapes and I hate to say it, digital,

then we can relax on amps because who really needs to have
0.02% at listening levels when 0.2% is OK?
The total system thd including recording and replay gear including speakers
can just get under 0.2% at all times, so there isn't any use worrying
about a high distortion amplifier making what may have been 4% dreadful in 1947
more dreadful.
Some would say this is a cop out and compromise idea,
but few folks would recognise whether the global NFB is connected or not
in a W amp in a listening test, and especially if the W amp has
a quad of KT88/KT90 in triode in its output stage.

The Hafler and Keroes ideas about local cathode feedback
seem a step forward because when well implemented the result
is rather good. And better than Quad II.

The Quad II is a nice idea, but really I have never regarded Quad II as any more
than a chic toy boy amp
needing a shove to get it to grow up.
The Quad 40 would have to be a better amp.

But well before there was ever to be another tube amp from Quad after Quad II,
the world and Quad turned to solid state.
There would be many who'd say hooray, and what fine solid state amps
were made by Quad, and that any of them can hold their own with anything made now.

I leave such people in peace to celebrate; I will still dissappear
to gather around me some glassware which I care for enough to keep it on the road
without much effort, and without a huge insidious build up of N&D
from lack of care.
And I prefer the fidelity of tubes and don't care a hoot that the measurement
zealots
go all foamy at the mouth over numbers, the numbers don't explain the
phenomena of tube use being good.



It is all a matter of where
you're looking from. You might, for instance, consider the Williamson
and then the Quad II as the zenith of hi-fi, with a long cheapening
decline into silicon; it is an equally valid view (and depends, always,
on which speakers you have in mind to use with their amps...).


The initial solid state gear was based around germanium.
What a horror story it was for 10 years.
Then in about 1960, silicon became king overnight.

The early germanium and silicon was accepted very eargerly by the public
because 2 channel stereo arrived with it, which allowed imaging,
another facet of hi-fi. The sound quality from the SS was no worse than
the poorly serviced old ageing tube amps people were reluctant to re-tube, service
properly,
and duplicate for stereo.
Many Quad II amps I have serviced in the last 10 years had very serious
faults such as one KT66 with 30mA, the other just slightly red with 90mA,
and even without this ****ty fault the imbalance of matching of EF86
and KT66 meant that THD was just as if there was no global NFB connected or worse.

Sound was very lack lustre indeed.
The same can be said for ALL the dear old junk made between 1947 and 1957.



In general, these men were driven by external events in a marketplace,
and it is in the external events we must seek our answer.


Indeed the market place corrupts all ideals; greed rules!

But if any here want to take the purist line and make speakers and amplifiers
without compromises that were routinely addopted to cheapen a product's
cost of production and distribution, then they can do so now.
Maybe they cannot ever build a car in their back yard, but they
can build a hi-fi system.

They still need to find decent recordings to play to enjoy their system,
and like the jerks who make some CDs are to blame for dissappointments
discerning memebrs of my dad's generation were appalled
by some of the vinyl and tape offerings one over spent on.
In any collection of vinyl I eagerly accept as gifts now there is a mixture
of gems and dross.

Patrick Turner.






Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review


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HP HP is offline
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Default Explanation still required for triode superiority

"Andre Jute" wrote in message ups.com...
My point is a little more subtle. I see an effect which looks like NFB
happening between the terminals of a triode; I'm happy to call it
internal or natural NFB until someone else offers an explanation that
justifies giving it another name; no one offers such an explanation,
merely negative objections to naming it NFB; until they pull their
finger from their arse and say something positive (and more cogent)
than Patrick, who *does* have a case, I shall not change my mind just
because they're "agin".


The effect you see is the change in plate current with plate voltage. This
is exactly the definition of plate resistance, which is both the name and
the explanation that have been in standard use for the past seven decades
or so.

In actual fact there is no external observation you can make of the triode
that proves, or even suggests, there is internal negative feedback at work
inside the tube. Everything you see can be more simply and economically
explained by the Thevenin or Norton models.

Thevenin, Norton, and the NFB conjecture are all just fictional models
that help to describe or predict the tube's external behavior. None of
them represents the actual physical processes at work inside the tube,
and it is a mistake to claim otherwise. The Child-Langmuir equation,
which is based on the distribution of electric fields and charge density
inside the tube is another model, and arguably as good an explanation
of tube behavior as we need. There's nothing in it that depends on
negative feedback, either.

This is fundamentally an engineering debate and the arguments are
necessarily framed in engineering terms. The fact that technical language
is used to express a point doesn't make the point true by default. The
assumptions and inferences have to be grounded in fact and logic to be
valid. The challenge is to define who's qualified to decide what is factual
and logical in an engineering argument. An engineer perhaps?

I would be delighted to debate this subject, point by point, in front of
a qualified and neutral judge (or panel of judges) from the tube audio
engineering community. How about Steve Bench, John Atwood, Lynn
Olson, or Morgan Jones?

-Henry


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Default Explanation still required for triode superiority

"Impedance is futile, you will be simulated into the triode of the
Borg"... :-)
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Andre Jute Andre Jute is offline
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Thanks for writing in, HP. I happen to agree with you, the model isn't
real life. But it is the nearest we have to the vacuum inside the tube.
I've already given this a good bash, and everyone else is bored with
it. You can find my conclusions at
http://members.lycos.co.uk/fiultra/K...dre%20Jute.htm
and
http://members.lycos.co.uk/fiultra/K...dre%20Jute.htm
If those you want as referees wish to come on RAT to give us the
benefit of their wisdom, we should be delighted to welcome them (or
welcome some of them back, as Steve for instance is an old RAT). But
bringing them here specifically for a contentious debate is simply
likely to drive them out again in short order; in fact, I haven't heard
a dumber idea all week, and we've had quite a few dillies already.

I was entertained by your suggestion that we should believe "an
engineer perhaps". Perhaps is right. For every good engineer we get on
RAT, we seem to get three rotters. Only recently we had Pinkerton,
Krueger and Poopie Stevenson, blustering tenth-raters every one of
them. The rot on RAT set in with one Henry Pasternack, who bragged
about a master's degree in electronics from Stanford; this clown
Pasternack was so thickly unscientific that in our first exchange I
caught him out by trailing before him 90 plus observations on 30 plus
amps -- *which he never asked to see*; he didn't even discover for
another ten months why the decent engineers were treating him with
disdain. See the section WHO HAS A "FULL UNDERSTANDING"?, when you
get to:
http://groups.google.ie/group/rec.au...af253a7e070591
Pasternack was the "engineer" locally known as Pompass Plodnick, for
the obvious reasons; he's also the one who notoriously tried to excuse
lies on professional matters as merely (!) "my zeal to flame Andre".

You can see why after our experience with Pasternack, the very paradigm
of a diplomaed quarterwit, we now expect more proof of scientific and
personal honesty from an engineer than merely that he waves a diploma.

Hang around, HP; start a bit smaller than such contentious subjects as
NFB and triode superiority -- and you might even last longer than a
week. A sense of humour and a copy of the RDH helps. Don't let the RDH
frighten you off by its size; see my article here for a guide on which
parts of the RDH you need to read:
http://members.lycos.co.uk/fiultra/J...MPS%20RDH.html

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review


HP wrote:
"Andre Jute" wrote in message ups.com...
My point is a little more subtle. I see an effect which looks like NFB
happening between the terminals of a triode; I'm happy to call it
internal or natural NFB until someone else offers an explanation that
justifies giving it another name; no one offers such an explanation,
merely negative objections to naming it NFB; until they pull their
finger from their arse and say something positive (and more cogent)
than Patrick, who *does* have a case, I shall not change my mind just
because they're "agin".


The effect you see is the change in plate current with plate voltage. This
is exactly the definition of plate resistance, which is both the name and
the explanation that have been in standard use for the past seven decades
or so.

In actual fact there is no external observation you can make of the triode
that proves, or even suggests, there is internal negative feedback at work
inside the tube. Everything you see can be more simply and economically
explained by the Thevenin or Norton models.

Thevenin, Norton, and the NFB conjecture are all just fictional models
that help to describe or predict the tube's external behavior. None of
them represents the actual physical processes at work inside the tube,
and it is a mistake to claim otherwise. The Child-Langmuir equation,
which is based on the distribution of electric fields and charge density
inside the tube is another model, and arguably as good an explanation
of tube behavior as we need. There's nothing in it that depends on
negative feedback, either.

This is fundamentally an engineering debate and the arguments are
necessarily framed in engineering terms. The fact that technical language
is used to express a point doesn't make the point true by default. The
assumptions and inferences have to be grounded in fact and logic to be
valid. The challenge is to define who's qualified to decide what is factual
and logical in an engineering argument. An engineer perhaps?

I would be delighted to debate this subject, point by point, in front of
a qualified and neutral judge (or panel of judges) from the tube audio
engineering community. How about Steve Bench, John Atwood, Lynn
Olson, or Morgan Jones?

-Henry


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Eeyore Eeyore is offline
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Default Explanation still required for triode superiority



robert casey wrote:

"Impedance is futile, you will be simulated into the triode of the
Borg"... :-)


Reluctance will not be tolerated.

Graham




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Patrick Turner Patrick Turner is offline
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HP wrote:

"Andre Jute" wrote in message ups.com...
My point is a little more subtle. I see an effect which looks like NFB
happening between the terminals of a triode; I'm happy to call it
internal or natural NFB until someone else offers an explanation that
justifies giving it another name; no one offers such an explanation,
merely negative objections to naming it NFB; until they pull their
finger from their arse and say something positive (and more cogent)
than Patrick, who *does* have a case, I shall not change my mind just
because they're "agin".


The effect you see is the change in plate current with plate voltage. This
is exactly the definition of plate resistance, which is both the name and
the explanation that have been in standard use for the past seven decades
or so.

In actual fact there is no external observation you can make of the triode
that proves, or even suggests, there is internal negative feedback at work
inside the tube. Everything you see can be more simply and economically
explained by the Thevenin or Norton models.

Thevenin, Norton, and the NFB conjecture are all just fictional models
that help to describe or predict the tube's external behavior. None of
them represents the actual physical processes at work inside the tube,
and it is a mistake to claim otherwise. The Child-Langmuir equation,
which is based on the distribution of electric fields and charge density
inside the tube is another model, and arguably as good an explanation
of tube behavior as we need. There's nothing in it that depends on
negative feedback, either.


Professor child called the mutual effect of anode AND grid voltages
in a triode a form of "self regulation".
See Radio Engineering, by Terman, 1937.

He does not call it NFB probably because it would have confused ppl at the time
who were used to NFB ONLY being some external networking to
get an amp of device to display lower Ra thd etc than otherwise it would
without NFB.

The observation of a triode as a mystery 3 terminal device could be
argued to contain NFB.

When you have a 300B with Ia = 70mA, Ea = +400V,
then if it acted like a resistor without NFB the R value
would be 400 / 0.07 = 5,700 ohms.
But where one maintains the grid bias voltage and fixes the cathode voltage,
abd simply raises the anode voltage by say 80V,
then one soon finds that the Ia change = 100mA, and
it is because the Ra = 800 ohms, and not the 5,700 ohms of quiescent Ea / Ia .
How can this be? Its because the anode has a massive effect on the
flow of electrons from the space charge around the cathode to anode despite
grid voltage's supposed control of current.

One simply cannot deny that a huge anode feedback effect exists,
and where you have a grid also able to control the Ia
with a gm of about 5mA/V then there MUST be a summing of the anode and grid voltage effects
according to some formula ( upon which Professor Child throws more light than I do ) .

So its very easy to see that NFB is alive and operational in a triode.

Because its self contained, there is no need to always represent the triode with symbols
to represent the NFB network that exists, it merely is represented by
the normal symbol but considered with Ra, µ, and gm WITH NFB being effective;
Thge triode cannot be considered without its NFB unless one makes a mental
model of a perfect pentode with NFB.
The perfect pentode BTW is an unusual animal because it'd assume Ra would be infinite,
and since µ = gm x Ra, then perfect pentode µ also would be infinite,
so that a mild external loop of NFB would render such a pentode circuit free of any THD
because the gain reduction with NFB would also be infinite.
But alas, no such perfect pentode exists. The anode voltage still always
has some effect on the Ia even with a screen present.



This is fundamentally an engineering debate and the arguments are
necessarily framed in engineering terms. The fact that technical language
is used to express a point doesn't make the point true by default. The
assumptions and inferences have to be grounded in fact and logic to be
valid. The challenge is to define who's qualified to decide what is factual
and logical in an engineering argument. An engineer perhaps?


I am not a qualified university educated triodologist.

But my powers of observation reveal NFB in triodes to me.

But by exactly what process in purely technical terms would you use to
allege NFB does NOT exist in triodes?



I would be delighted to debate this subject, point by point, in front of
a qualified and neutral judge (or panel of judges) from the tube audio
engineering community. How about Steve Bench, John Atwood, Lynn
Olson, or Morgan Jones?


The above list may not wish to join our little discussions because the
morons and arsoles wait impatiently with buckets of ****
to drench any attempts of true intellectual discourse and democracy.

Patrick Turner.


-Henry


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Dominique Michel Dominique Michel is offline
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Posts: 7
Default Explanation still required for triode superiority

Le 25 Sep 2006 12:51:12 -0700,
"Bret Ludwig" a Ă©crit :


Peter Wieck wrote:
Andrew Jute McCoy wrote its usual fallacious arguments:

Called "begging the question".

Triodes are neither "superior" nor "inferior" when it comes to
amplifiers. However, they do have many difficulties. Not the least of
which a

Flea Power.
Expensive to create.
Difficult to make operational (as your model so clearly illustrated).


Triodes are cheaper to build than beam power tubes of a given size,
simpler, and can be used for amplifiers of any size. Most 50 kW AM
broadcast transmitters had two triodes in their modulators giving 30 kW
audio power in Class B.

The common 811 available under $20, though not an ideal tube, can give
200 easy watts for a pair. As can 211s, 845s, etc. The GEC book shows
a 1 KW audio amp with a pair of largish glass triodes.

Difficult to use? Just give them a filament supply of several amps,
preferably from a filament transformer with shunts designed for that
tube, a few kV on the plate and enough drive and they work fine.


Audio is not only about power and characteristics on the paper, but about
sound. Most if not all high power tubes are designed for high frequency
transmitters, not for high-fidelity, and they will sound very poorly when used
for an audio amp.

You will get a much better sound when using 4, 6 or 8 EL34 or 300B as only 2
more powerful tubes.

Now, the controversy between pentode and triode is not new. If you look, most
of the so called pentodes used in high fidelity audio are in fact beam-tetrodes.
The main problem with the pentode is its high output impedance. The main
problem with the triode is its low sensibility. The beam tetrode try to get most
of the advantages of the triode as its relatively low output impedance and most
of the advantages of the pentode as its high sensibility. And the result is a
very good tube for power amplification.

But if you want to get a good result in audio with a beam tetrode, you must be
very careful with the design. A triode design is easier because you don't have
the g2. A good practice, if you are using a fixed g2 voltage, is to stabilize
it. Just be doing it, the amp will archive at least a 2 time better dynamic at
the output. But how many amps on the market are using a stabilized Vg2?

Almost no one because it cost more money to build.

Another issue, and not only with the beam tetrode, is the quality of the
tubes. Take the 6L6. It is hundred of different brands, but only a little part
of those brands have a really good quality of manufacturing. It is in theory
the same tube as a 807. Make an amp with 2 x 807, 600V DC on the middle of the
output transformer when the amp is at full output, 300 V DC on the g2, and
replace the 807 by 6L6 tubes. Most of them will just glow up at full output. And
already at low level, they will arc inside the tube because of a too high Va,
and this will sound like hell in the loudspeaker.

Take a preamp tube as the ECC83-12AX7. Buy a few tubes of different brands. You
will get as many sound at the output as brands. In fact even more, because with
the cheaper brands, different tubes will sound differently.

So, when you want to compare tubes, you must not only say the type of the
tubes, but the brand too. And when comparing tubes as different as a triode and
a pentode, you must talk about the topology of the circuits. A good quality
pentode will sound better as a poor quality triode. And a pentode used in a
deign that have a good topology will sound better as a triode of the same
quality but used in a circuit with a poor design.
--
Dominique Michel
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Phil Phil is offline
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Posts: 80
Default Explanation still required for triode superiority

Patrick Turner wrote:

[snip]


Professor child called the mutual effect of anode AND grid voltages
in a triode a form of "self regulation".
See Radio Engineering, by Terman, 1937.

He does not call it NFB probably because it would have confused ppl at the time
who were used to NFB ONLY being some external networking to
get an amp of device to display lower Ra thd etc than otherwise it would
without NFB.

The observation of a triode as a mystery 3 terminal device could be
argued to contain NFB.

When you have a 300B with Ia = 70mA, Ea = +400V,
then if it acted like a resistor without NFB the R value
would be 400 / 0.07 = 5,700 ohms.
But where one maintains the grid bias voltage and fixes the cathode voltage,
abd simply raises the anode voltage by say 80V,
then one soon finds that the Ia change = 100mA, and
it is because the Ra = 800 ohms, and not the 5,700 ohms of quiescent Ea / Ia .
How can this be? Its because the anode has a massive effect on the
flow of electrons from the space charge around the cathode to anode despite
grid voltage's supposed control of current.

One simply cannot deny that a huge anode feedback effect exists,
and where you have a grid also able to control the Ia
with a gm of about 5mA/V then there MUST be a summing of the anode and grid voltage effects
according to some formula ( upon which Professor Child throws more light than I do ) .

So its very easy to see that NFB is alive and operational in a triode.

[snip]

I am not a qualified university educated triodologist.

But my powers of observation reveal NFB in triodes to me.

But by exactly what process in purely technical terms would you use to
allege NFB does NOT exist in triodes?


Patrick, you're simply being stubborn at this point. We have pointed
out, over and over, that a plate resistance, which, so far, you CANNOT
and HAVE NOT proven does not exist, can account for all of the "feedback
effects," by which you mean damping, that you talk about. Yes, in the
absence of tests which possibly can distinguish between anode resistance
and triode feedback, we really don't know which it is. But to claim that
feedback must exist *because* effects equivalent to either feedback or
low plate resistance exist is unscientific. You have a choice, and that
is why the rest of us simply state that, in the absence of any logical,
intellectual, or engineering advantage for feedback, we prefer low plate
resistance as a *model*. That's our choice. Maybe the other choice is
better. But you have not given any analysis to my knowledge which proves
that such a choice does not exist, or even that a feedback model is a
better choice for audio or electronics.

Phil
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Andre Jute Andre Jute is offline
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Posts: 1,661
Default Explanation still required for triode superiority

Hi, Dominique. Welcome to RAT. I'm Andre Jute. This is my thread.

You say:
The main problem with the triode is its low sensibility.


Actually, the great advantage of the triode (or trioded pentodes like
the EL34) is its *high* sensibility with the music, that is the
natural, unaffected way it reproduces it.

You probably mean "low power". That mainly bothers people who haven't
put their minds in gear. Once you have sensitive speakers, 300B are
overkill on Lowther horns already. Alternatively, when I wanted a
triode single-ended amp to drive Quad ESL63, I built it with
transmitting triodes to give 80W from a standard 2Vrms CD output
(417A::300B::PSE SV572-3 or -10 does the biz in only three ZNFB
stages). If you're willing to pay the price, everything is possible and
nothing is a barrier.

As examples of why the low power of the commoner triodes is not a
problem, here are some bicor horns I built for Lowther drivers:
http://members.lycos.co.uk/fiultra/K...20T91HWAF3.jpg
to use with either of these 300B
http://members.lycos.co.uk/fiultra/T...trafi-crct.jpg
http://members.lycos.co.uk/fiultra/T44bis-'Populaire'-crct.jpg
but here is 0.3W quality amp that drives the Lowthers very pleasingly
indeed:
http://members.lycos.co.uk/fiultra/K...0T68MZ417A.jpg
http://members.lycos.co.uk/fiultra/t...17acircuit.jpg
http://members.lycos.co.uk/fiultra/t68bismzlayout.jpg
or if you want good quality and more power for less money, here is a 2W
trioded EL34 amp I designed for students:
http://members.lycos.co.uk/fiultra/Jute-EL34-SEntry.jpg
to use with this inexpensive but very sensitive (and sensible!)
speaker:
http://members.lycos.co.uk/fiultra/K...Impresario.jpg

All becomes clear when you give up being a fashion-victim of people who
think more power is better power because they are too lazy or stupid to
design within the parameters of the best-sounding components; some are
too thick even to work out that it is the sound that matters, not the
engineering, and of those we have a surplus already on RAT. You might
enjoy "The myth of the Watt:", or then again, not, as the case might
be:
http://members.lycos.co.uk/fiultra/K...dre%20Jute.htm

More on my main site, URL under my sig.

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review


Dominique Michel wrote:
Le 25 Sep 2006 12:51:12 -0700,
"Bret Ludwig" a écrit :


Peter Wieck wrote:
Andrew Jute McCoy wrote its usual fallacious arguments:

Called "begging the question".

Triodes are neither "superior" nor "inferior" when it comes to
amplifiers. However, they do have many difficulties. Not the least of
which a

Flea Power.
Expensive to create.
Difficult to make operational (as your model so clearly illustrated).


Triodes are cheaper to build than beam power tubes of a given size,
simpler, and can be used for amplifiers of any size. Most 50 kW AM
broadcast transmitters had two triodes in their modulators giving 30 kW
audio power in Class B.

The common 811 available under $20, though not an ideal tube, can give
200 easy watts for a pair. As can 211s, 845s, etc. The GEC book shows
a 1 KW audio amp with a pair of largish glass triodes.

Difficult to use? Just give them a filament supply of several amps,
preferably from a filament transformer with shunts designed for that
tube, a few kV on the plate and enough drive and they work fine.


Audio is not only about power and characteristics on the paper, but about
sound. Most if not all high power tubes are designed for high frequency
transmitters, not for high-fidelity, and they will sound very poorly when used
for an audio amp.

You will get a much better sound when using 4, 6 or 8 EL34 or 300B as only 2
more powerful tubes.

Now, the controversy between pentode and triode is not new. If you look, most
of the so called pentodes used in high fidelity audio are in fact beam-tetrodes.
The main problem with the pentode is its high output impedance. The main
problem with the triode is its low sensibility. The beam tetrode try to get most
of the advantages of the triode as its relatively low output impedance and most
of the advantages of the pentode as its high sensibility. And the result is a
very good tube for power amplification.

But if you want to get a good result in audio with a beam tetrode, you must be
very careful with the design. A triode design is easier because you don't have
the g2. A good practice, if you are using a fixed g2 voltage, is to stabilize
it. Just be doing it, the amp will archive at least a 2 time better dynamic at
the output. But how many amps on the market are using a stabilized Vg2?

Almost no one because it cost more money to build.

Another issue, and not only with the beam tetrode, is the quality of the
tubes. Take the 6L6. It is hundred of different brands, but only a little part
of those brands have a really good quality of manufacturing. It is in theory
the same tube as a 807. Make an amp with 2 x 807, 600V DC on the middle of the
output transformer when the amp is at full output, 300 V DC on the g2, and
replace the 807 by 6L6 tubes. Most of them will just glow up at full output. And
already at low level, they will arc inside the tube because of a too high Va,
and this will sound like hell in the loudspeaker.

Take a preamp tube as the ECC83-12AX7. Buy a few tubes of different brands. You
will get as many sound at the output as brands. In fact even more, because with
the cheaper brands, different tubes will sound differently.

So, when you want to compare tubes, you must not only say the type of the
tubes, but the brand too. And when comparing tubes as different as a triode and
a pentode, you must talk about the topology of the circuits. A good quality
pentode will sound better as a poor quality triode. And a pentode used in a
deign that have a good topology will sound better as a triode of the same
quality but used in a circuit with a poor design.
--
Dominique Michel


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Henry Pasternack Henry Pasternack is offline
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Posts: 13
Default Explanation still required for triode superiority

"Patrick Turner" wrote in message ...
HP wrote:


I've corrected the ID in my news client profile.

Professor child called the mutual effect of anode AND grid voltages in a triode
a form of "self regulation". See Radio Engineering, by Terman, 1937.


I've read that book in the library, but don't have a copy of my own, so I can't
really say for sure out of context what Terman meant by "self regulation". In
the past, I've responded to this point by giving examples of systems that can
be called "self-regulating", but where the regulation is the result of a dynamic
equilibrium rather than negative feedback. The spinning electric motor and the
falling parachute are two examples, but many others can be proposed.

I've also shown before how models of rate-limited systems, like the electric
motor or even a plain resistor, can be refactored into equivalent negative
feedback systems. But the feedback models don't add any information that
we can't, in general, get from simpler models, and with much less effort. The
same is true of triodes and feedback. Norton and Thevenin have the same
predictive power as the feedback model, but are simpler and more useful.

Please take note, I'm not arguing that the triode cannot be described in terms
of negative feedback. What I am arguing is that this is a contrived and largely
pointless complication. I am also showing how other models, both external
and internal, can give us the same information about the tube without the need
to invoke negative feedback. Finally, I am pointing out the inconsistencies,
errors, and omissions in your own statements.

The observation of a triode as a mystery 3 terminal device could be argued
to contain NFB.

When you have a 300B with Ia = 70mA, Ea = +400V, then if it acted like a
resistor without NFB the R value would be 400 / 0.07 = 5,700 ohms. But
where one maintains the grid bias voltage and fixes the cathode voltage, abd
simply raises the anode voltage by say 80V, then one soon finds that the Ia
change = 100mA, and it is because the Ra = 800 ohms, and not the 5,700
ohms of quiescent Ea / Ia . How can this be? Its because the anode has a
massive effect on the flow of electrons from the space charge around the
cathode to anode despite grid voltage's supposed control of current.


You get the exact same result if you represent the tube as an 800 Ohm resistor
in series with a 344V battery, and no feedback is required. This is the Thevenin
model. While your result is not inconsistent with feedback, the existence of an
alternate model means your results cannot "prove" there is NFB in the triode.
As I keep saying, any attempt to "prove" the existence of NFB in the tube by
external observation is fallacious from the get-go. You should read and think
about this carefully because it's a fundamental point.

One simply cannot deny that a huge anode feedback effect exists, and where
you have a grid also able to control the Ia with a gm of about 5mA/V then there
MUST be a summing of the anode and grid voltage effects according to some
formula ( upon which Professor Child throws more light than I do ) .

So its very easy to see that NFB is alive and operational in a triode.


But I certainly can deny it. I hope you'll agree the mechanism at work here is the
same even if we impose the condition of linearity. And if this is true, then by the
principle of superposition we can separate out the effects of the control grid and
the plate and analyze them separately. The control grid, clearly, is analgous to
the non-inverting input on the op-amp. It's in the forward path, so we can ignore
it. In fact, we can tie the control grid to the cathode, or remove it entirely, and
the analysis stays the same. And this takes us back to the diode argument and
your inconsistent interpretation of plate resistance.

Your observation about the summing of the effects of the control grid and the
plate is really the crux of your argument because it's the only statement you've
ever made to justify that negative feedback occurs. But the argument can't be
valid, as I've shown, because it fails to acknowledge the principle of superposition.
Superposition says that the summing is irrelevant because the effects of the grid
and the plate can be treated separately. This is why the point about the diode
is so important.

Thee triode cannot be considered without its NFB unless one makes a mental
model of a perfect pentode with NFB.


This isn't true at all, and is a perfect example of "begging the question", or taking
the conclusion of an argument as one of its premises. We are trying to evaluate
the claim that triodes have internal negative feedback. Declaring, a priori, that a
pentode is a triode with negative feedback removed, and showing that adding
feedback to the pentode transforms it into a triode begs the question since it
depends on the presumption that the triode had negative feedback in the first
place.

The simple, non-feedback explanation for triode behavior is as follows. The
plate voltage establishes an electric field, and therefore a potential gradient, at
the surface of the cathode that draws electrons out of the cathode and sweeps
them toward the plate. The electrons are rapidly emitted into the vicinity of the
cathode until the potential gradient, by Poisson's equation, reaches zero. At
this point, the net rate of electron emission from the cathode equals the rate at
which electrons are swept to the plate and the plate current settles into a steady
equilibrium. Increasing or decreasing the plate voltage throws the system out
of equilibrium and the plate current varies upward or downward until the
equilibrium is reestablished at a new operating point.

You can call this negative feedback if you want and you won't be incorrect.
But in doing so, you should be prepared to accept that many, many other
natural systems are also examples of negative feedback, not the least of which
is the lowly vacuum diode. You also won't be excluding interpretations that
do not depend on the presumption of feedback.

[Pentode coments deleted]


Irrelevant.

I am not a qualified university educated triodologist.


True. I would never say that someone needs a university degree to learn to
build audio gear. You are a perfect case in point, Patrick, how someone
without a Triodology degree can become an accomplished tube technician
and a prolific designer. But you need to understand, no matter how broad
your practical experience may be, that there are limits to your conceptual
knowledge. For instance, your example with the 300B above tells me you
are confused about the difference between small-signal and large-signal
circuit analysis. This isn't a minor error, either. It's a giant, sucking hole in
your argument.

But my powers of observation reveal NFB in triodes to me.


Yes, and to a fundamentalist Christian, the diversity of species reveals the
wonder and glory of creation and thereby proves the existence of God. But
that doesn't qualify him to be a biologist (much as he may think so).

But by exactly what process in purely technical terms would you use to
allege NFB does NOT exist in triodes?


I believe I've answered that question many times over the past few days.
I can't help you if you didn't understand. I have a rule I call the "Law of
Conservation of Complexity". It says for any given topic there is a lower
bound to how simple a valid explanation can be. If the audience lacks the
sophistication to follow along at that level, than no explanation, no matter
how correct and clear, will ever make sense to that audience.

The above list may not wish to join our little discussions because the
morons and arsoles wait impatiently with buckets of **** to drench any
attempts of true intellectual discourse and democracy.


On that point, you won't get any disagreement from me. Although we might
not see eye-to-eye when it comes to assigning blame to specific individuals.

-Henry




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Patrick Turner Patrick Turner is offline
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Default Explanation still required for triode superiority



Dominique Michel wrote:

Le 25 Sep 2006 12:51:12 -0700,
"Bret Ludwig" a Ă©crit :


Peter Wieck wrote:
Andrew Jute McCoy wrote its usual fallacious arguments:

Called "begging the question".

Triodes are neither "superior" nor "inferior" when it comes to
amplifiers. However, they do have many difficulties. Not the least of
which a

Flea Power.
Expensive to create.
Difficult to make operational (as your model so clearly illustrated).


Triodes are cheaper to build than beam power tubes of a given size,
simpler, and can be used for amplifiers of any size. Most 50 kW AM
broadcast transmitters had two triodes in their modulators giving 30 kW
audio power in Class B.

The common 811 available under $20, though not an ideal tube, can give
200 easy watts for a pair. As can 211s, 845s, etc. The GEC book shows
a 1 KW audio amp with a pair of largish glass triodes.

Difficult to use? Just give them a filament supply of several amps,
preferably from a filament transformer with shunts designed for that
tube, a few kV on the plate and enough drive and they work fine.


Audio is not only about power and characteristics on the paper, but about
sound. Most if not all high power tubes are designed for high frequency
transmitters, not for high-fidelity, and they will sound very poorly when used
for an audio amp.


I doubt this is correct. There are many examples where a tube can be used
equally appropriately for RF or AF.
The 211 makes a nice transmit tube and can be superlative as an audio tubes.
813 is another.....



You will get a much better sound when using 4, 6 or 8 EL34 or 300B as only 2
more powerful tubes.


Ain't necessarily so...



Now, the controversy between pentode and triode is not new. If you look, most
of the so called pentodes used in high fidelity audio are in fact beam-tetrodes.
The main problem with the pentode is its high output impedance. The main
problem with the triode is its low sensibility.


Perhaps you mean sensitivity, or voltage gain. Its a very sensible choice for an
output device....

The beam tetrode try to get most
of the advantages of the triode as its relatively low output impedance and most
of the advantages of the pentode as its high sensibility. And the result is a
very good tube for power amplification.


???



But if you want to get a good result in audio with a beam tetrode, you must be
very careful with the design. A triode design is easier because you don't have
the g2. A good practice, if you are using a fixed g2 voltage, is to stabilize
it. Just be doing it, the amp will archive at least a 2 time better dynamic at
the output. But how many amps on the market are using a stabilized Vg2?


The use of a slow time constant with RC filter used for g2 supply is all that is
required for
AB audio amps with multi grids because in fact the Eg2 variation at average power =
1/10
of clipping power is very small.



Almost no one because it cost more money to build.


I shunt regulate my screen supplies. A few 75V x 5 watt zener diodes and a power
resistor of 10W is usually
all that is needed.



Another issue, and not only with the beam tetrode, is the quality of the
tubes. Take the 6L6. It is hundred of different brands, but only a little part
of those brands have a really good quality of manufacturing. It is in theory
the same tube as a 807. Make an amp with 2 x 807, 600V DC on the middle of the
output transformer when the amp is at full output, 300 V DC on the g2, and
replace the 807 by 6L6 tubes. Most of them will just glow up at full output. And
already at low level, they will arc inside the tube because of a too high Va,
and this will sound like hell in the loudspeaker.


Maybe depends which type of 6L6 one uses....



Take a preamp tube as the ECC83-12AX7. Buy a few tubes of different brands. You
will get as many sound at the output as brands. In fact even more, because with
the cheaper brands, different tubes will sound differently.

So, when you want to compare tubes, you must not only say the type of the
tubes, but the brand too. And when comparing tubes as different as a triode and
a pentode, you must talk about the topology of the circuits. A good quality
pentode will sound better as a poor quality triode. And a pentode used in a
deign that have a good topology will sound better as a triode of the same
quality but used in a circuit with a poor design.
--
Dominique Michel


Tubes brands do make different sound amoung the same type number
and using pentodes in lieu of triodes ditto.

Tubecraft involves many variables around simple ideas.

Its all so much easier than class D DIY PWM amps....

Patrick Turner.


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Patrick Turner Patrick Turner is offline
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Default Explanation still required for triode superiority



Phil wrote:

Patrick Turner wrote:

[snip]


Professor child called the mutual effect of anode AND grid voltages
in a triode a form of "self regulation".
See Radio Engineering, by Terman, 1937.

He does not call it NFB probably because it would have confused ppl at the time
who were used to NFB ONLY being some external networking to
get an amp of device to display lower Ra thd etc than otherwise it would
without NFB.

The observation of a triode as a mystery 3 terminal device could be
argued to contain NFB.

When you have a 300B with Ia = 70mA, Ea = +400V,
then if it acted like a resistor without NFB the R value
would be 400 / 0.07 = 5,700 ohms.
But where one maintains the grid bias voltage and fixes the cathode voltage,
abd simply raises the anode voltage by say 80V,
then one soon finds that the Ia change = 100mA, and
it is because the Ra = 800 ohms, and not the 5,700 ohms of quiescent Ea / Ia .
How can this be? Its because the anode has a massive effect on the
flow of electrons from the space charge around the cathode to anode despite
grid voltage's supposed control of current.

One simply cannot deny that a huge anode feedback effect exists,
and where you have a grid also able to control the Ia
with a gm of about 5mA/V then there MUST be a summing of the anode and grid voltage effects
according to some formula ( upon which Professor Child throws more light than I do ) .

So its very easy to see that NFB is alive and operational in a triode.

[snip]

I am not a qualified university educated triodologist.

But my powers of observation reveal NFB in triodes to me.

But by exactly what process in purely technical terms would you use to
allege NFB does NOT exist in triodes?


Patrick, you're simply being stubborn at this point. We have pointed
out, over and over, that a plate resistance, which, so far, you CANNOT
and HAVE NOT proven does not exist, can account for all of the "feedback
effects," by which you mean damping, that you talk about.


The Ea / Ia at the quiecent state = 5,700 ohms for the 300B I mentioned.
But why does it measure 800 ohms when small variations in Ea are made?

if there was no FB and the tube was just a purely passive device like a resistor,
the changes in Ea would give Ra = 5,700 ohms.
but we get 800 ohms.
How come?


Yes, in the
absence of tests which possibly can distinguish between anode resistance
and triode feedback, we really don't know which it is. But to claim that
feedback must exist *because* effects equivalent to either feedback or
low plate resistance exist is unscientific. You have a choice, and that
is why the rest of us simply state that, in the absence of any logical,
intellectual, or engineering advantage for feedback, we prefer low plate
resistance as a *model*. That's our choice. Maybe the other choice is
better. But you have not given any analysis to my knowledge which proves
that such a choice does not exist, or even that a feedback model is a
better choice for audio or electronics.


You call me stubborn, and refuse to proove I'm wrong, and you cannot deal with the idea
of the mutual effect of the two changing voltages of grid and anode which BOTH
have large effects on the Ia and so who is right?
If say I am wrong, then so is Prfessor Child, and all the guys with
better minds than yours or mine.

Where is you alternative modelling?

I see there is NFB in a triode not because I am stubborn, but because
it hits me in the eye as being so very obvious, and its missing from
all other devices.

Patrick Turner.




Phil


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Henry Pasternack Henry Pasternack is offline
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Default Explanation still required for triode superiority

"Andre Jute" wrote in message oups.com...
Thanks for writing in, HP. I happen to agree with you, the model isn't
real life. But it is the nearest we have to the vacuum inside the tube.
I've already given this a good bash, and everyone else is bored with
it. You can find my conclusions at
http://members.lycos.co.uk/fiultra/K...dre%20Jute.htm
and
http://members.lycos.co.uk/fiultra/K...dre%20Jute.htm


But these conclusions are wrong, as I've already proved. The "Jute Triode Effect"
is just your contrived name for "plate resistance", which physically is the result of
moving electrons giving up their kinetic energy as heat when they smash into the
plate. It has nothing to do with feedback.

You're welcome to post it on your website, but it doesn't mean you are right.
Sorry, that's just the way it is.

If those you want as referees wish to come on RAT to give us the
benefit of their wisdom, we should be delighted to welcome them (or
welcome some of them back, as Steve for instance is an old RAT).


Actually, it was a trick question. Steve Bench has already responded to my
postings on this subject. I'll leave it to you to look it up and see what he had
to say.

Have a good one.

-Henry


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Default Explanation still required for triode superiority



Henry Pasternack wrote:

"Patrick Turner" wrote in message ...
HP wrote:


I've corrected the ID in my news client profile.

Professor child called the mutual effect of anode AND grid voltages in a triode
a form of "self regulation". See Radio Engineering, by Terman, 1937.


I've read that book in the library, but don't have a copy of my own, so I can't
really say for sure out of context what Terman meant by "self regulation". In
the past, I've responded to this point by giving examples of systems that can
be called "self-regulating", but where the regulation is the result of a dynamic
equilibrium rather than negative feedback. The spinning electric motor and the
falling parachute are two examples, but many others can be proposed.


The self regulation is the combined net effect of the two active voltages in the triode,
one is the anode voltage, the other the grid voltage, and the two electrostatic fields
sum to give a net effect that governs Ia.



I've also shown before how models of rate-limited systems, like the electric
motor or even a plain resistor, can be refactored into equivalent negative
feedback systems. But the feedback models don't add any information that
we can't, in general, get from simpler models, and with much less effort. The
same is true of triodes and feedback. Norton and Thevenin have the same
predictive power as the feedback model, but are simpler and more useful.

Please take note, I'm not arguing that the triode cannot be described in terms
of negative feedback. What I am arguing is that this is a contrived and largely
pointless complication. I am also showing how other models, both external
and internal, can give us the same information about the tube without the need
to invoke negative feedback. Finally, I am pointing out the inconsistencies,
errors, and omissions in your own statements.

The observation of a triode as a mystery 3 terminal device could be argued
to contain NFB.

When you have a 300B with Ia = 70mA, Ea = +400V, then if it acted like a
resistor without NFB the R value would be 400 / 0.07 = 5,700 ohms. But
where one maintains the grid bias voltage and fixes the cathode voltage, abd
simply raises the anode voltage by say 80V, then one soon finds that the Ia
change = 100mA, and it is because the Ra = 800 ohms, and not the 5,700
ohms of quiescent Ea / Ia . How can this be? Its because the anode has a
massive effect on the flow of electrons from the space charge around the
cathode to anode despite grid voltage's supposed control of current.


You get the exact same result if you represent the tube as an 800 Ohm resistor
in series with a 344V battery, and no feedback is required. This is the Thevenin
model. While your result is not inconsistent with feedback, the existence of an
alternate model means your results cannot "prove" there is NFB in the triode.
As I keep saying, any attempt to "prove" the existence of NFB in the tube by
external observation is fallacious from the get-go. You should read and think
about this carefully because it's a fundamental point.


The triode indeed can be modelled as being equivalent to a super a low output impedance voltage generator
whose output voltage is µ x Vg, and then Ra is added as a series resistor.

This simple model of a triode does not include the NFB within the model, because there is no need to do so
since the NFB is contained within the 3 terminals, and for modelling
circuit gain the gene + Ra resistance is all one needs.





One simply cannot deny that a huge anode feedback effect exists, and where
you have a grid also able to control the Ia with a gm of about 5mA/V then there
MUST be a summing of the anode and grid voltage effects according to some
formula ( upon which Professor Child throws more light than I do ) .

So its very easy to see that NFB is alive and operational in a triode.


But I certainly can deny it. I hope you'll agree the mechanism at work here is the
same even if we impose the condition of linearity. And if this is true, then by the
principle of superposition we can separate out the effects of the control grid and
the plate and analyze them separately. The control grid, clearly, is analgous to
the non-inverting input on the op-amp. It's in the forward path, so we can ignore
it. In fact, we can tie the control grid to the cathode, or remove it entirely, and
the analysis stays the same. And this takes us back to the diode argument and
your inconsistent interpretation of plate resistance.


The grid isn't the non inverting input; the cathode is.

Anyway, the real analogy of a triode to an opamp
is one where the opamp has a high impedance shunt FB between the output
and input terminal and the actual connection to the opamp has a small
signal. So such an opamp may have open loop gain = 100,000 at 500Hz, and have a
1M output to actual opamp live inverting input connection, and say a 10k R between this input
which is called the virtual earth input, and the input to the amp as a whole including the FB loopP
If +10V appears at the opamp output, then -0.001 V is at the actual virtual earth input,
and current is 10V / 1,000k across the 1M, = 0.01mA.
So voltage across the 10k input resistance = 0.01 x 10 = 0.1V,
so amp input terminal signal = -0.101V, or about 1/100 of the output signal
because the ratio of FB resistors are 1:100.

In the triode the two arms of the shunt FB network are not resistances but are
elctrostatic fields which sum to form a virtual earth, or internal control point
which is a much lower voltage than the actual voltage applied to the grid
which is the input terminal of the amp at the front end of the shunt NFB network.



Your observation about the summing of the effects of the control grid and the
plate is really the crux of your argument because it's the only statement you've
ever made to justify that negative feedback occurs. But the argument can't be
valid, as I've shown, because it fails to acknowledge the principle of superposition.
Superposition says that the summing is irrelevant because the effects of the grid
and the plate can be treated separately. This is why the point about the diode
is so important.


But no grid exists in a diode.
Summing of bother grid and anode actually occurs; its not something I suppose occurs,
it really does occur.




Thee triode cannot be considered without its NFB unless one makes a mental
model of a perfect pentode with NFB.


This isn't true at all, and is a perfect example of "begging the question", or taking
the conclusion of an argument as one of its premises. We are trying to evaluate
the claim that triodes have internal negative feedback. Declaring, a priori, that a
pentode is a triode with negative feedback removed, and showing that adding
feedback to the pentode transforms it into a triode begs the question since it
depends on the presumption that the triode had negative feedback in the first
place.


I see the triode as being like a pentode but one with a resistance shunt NFB arrangement added to it.
There is a strong resemblance and in fact we can get a pentode to act almost exactly like
a triode with such a two resistance shunt NFB in terms of Rout,
THD, bw etc.
If one takes a 6AU6 one cann perform the experiment easily.
But the pentode with the two R shunt NFB is very different because the input resistance
is set by R1. In a triode, the input arm of the shunt NFB network is not a resistance but
is a high impedance voltage field.
Same with the anode field; it has very high impedance as well, but the two fields act effectively together
to give a net field effect on the flow of electrons from the space charge
gathered around the cathode.






The simple, non-feedback explanation for triode behavior is as follows. The
plate voltage establishes an electric field, and therefore a potential gradient, at
the surface of the cathode that draws electrons out of the cathode and sweeps
them toward the plate. The electrons are rapidly emitted into the vicinity of the
cathode until the potential gradient, by Poisson's equation, reaches zero. At
this point, the net rate of electron emission from the cathode equals the rate at
which electrons are swept to the plate and the plate current settles into a steady
equilibrium. Increasing or decreasing the plate voltage throws the system out
of equilibrium and the plate current varies upward or downward until the
equilibrium is reestablished at a new operating point.


This is about right; cathode emission can be many times Ia, but a state of equilibrium exists
as a result of the combined action of anode and grid voltages in the vicinity

Because there are TWO such opposing fields that control Ia, a shunt NFB network exists.



You can call this negative feedback if you want and you won't be incorrect.


Well that's all I ask people to believe.


But in doing so, you should be prepared to accept that many, many other
natural systems are also examples of negative feedback, not the least of which
is the lowly vacuum diode. You also won't be excluding interpretations that
do not depend on the presumption of feedback.


If there is MORE than one controlling field, NFB exists, but
where there is only ONE field, such as in a diode, then there is no NFB
and the device acts as a rather non linear resistance.





[Pentode coments deleted]


Irrelevant.

I am not a qualified university educated triodologist.


True. I would never say that someone needs a university degree to learn to
build audio gear. You are a perfect case in point, Patrick, how someone
without a Triodology degree can become an accomplished tube technician
and a prolific designer. But you need to understand, no matter how broad
your practical experience may be, that there are limits to your conceptual
knowledge. For instance, your example with the 300B above tells me you
are confused about the difference between small-signal and large-signal
circuit analysis. This isn't a minor error, either. It's a giant, sucking hole in
your argument.


I suggest you visit my educational pages at my website.

There are models of tubes as imaginery voltage amps with series R for Ra,
and NFB is explained as I have here.





But my powers of observation reveal NFB in triodes to me.


Yes, and to a fundamentalist Christian, the diversity of species reveals the
wonder and glory of creation and thereby proves the existence of God. But
that doesn't qualify him to be a biologist (much as he may think so).

But by exactly what process in purely technical terms would you use to
allege NFB does NOT exist in triodes?


I believe I've answered that question many times over the past few days.
I can't help you if you didn't understand. I have a rule I call the "Law of
Conservation of Complexity". It says for any given topic there is a lower
bound to how simple a valid explanation can be. If the audience lacks the
sophistication to follow along at that level, than no explanation, no matter
how correct and clear, will ever make sense to that audience.


Have ye not just mentioned that the triode is like a battery with Ra in series?
That is true what you say, but doesn't disprove NFB, which I say exists
despite the triode being able to be modelled as the battery + R,
or low Z generator + R.





The above list may not wish to join our little discussions because the
morons and arsoles wait impatiently with buckets of **** to drench any
attempts of true intellectual discourse and democracy.


On that point, you won't get any disagreement from me. Although we might
not see eye-to-eye when it comes to assigning blame to specific individuals.




Meanwhile, we merely need Ra, µ and gm values from the data sheets
to design good amps, and some Ra curves are also handy for various Eg values.
The data and curves are derived from the triode with its natural NFB in place IMHO,
and the amp maker does not need to know what the open loop characteristic gain of the triode would be if it
had its anode to space charge NFB arm completely and perfectly screened off
from having any effect.
Even in a pentode, there is a finite value for Ra; some small amount anode NFB still is in effect
The NFB is dramatically reduced by the screen.
One could use the screen to give a pentode almost infinite Ra by applying a slightly
positive FB signal to the screen.
The Ra could even be made into a negative resistance.
But such fiddles are all done with external loopings; none a doable
with natural electrode connections.


As long as we are discussing the issues peacefully, then all is well.
I'l agree to disagree at the finish without rancour and let others decide what they see as being true.

Patrick Turner.



-Henry


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Phil Phil is offline
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Default Explanation still required for triode superiority

Patrick Turner wrote:


Phil wrote:


Patrick Turner wrote:

[snip]


Professor child called the mutual effect of anode AND grid voltages
in a triode a form of "self regulation".
See Radio Engineering, by Terman, 1937.

He does not call it NFB probably because it would have confused ppl at the time
who were used to NFB ONLY being some external networking to
get an amp of device to display lower Ra thd etc than otherwise it would
without NFB.

The observation of a triode as a mystery 3 terminal device could be
argued to contain NFB.

When you have a 300B with Ia = 70mA, Ea = +400V,
then if it acted like a resistor without NFB the R value
would be 400 / 0.07 = 5,700 ohms.
But where one maintains the grid bias voltage and fixes the cathode voltage,
abd simply raises the anode voltage by say 80V,
then one soon finds that the Ia change = 100mA, and
it is because the Ra = 800 ohms, and not the 5,700 ohms of quiescent Ea / Ia .
How can this be? Its because the anode has a massive effect on the
flow of electrons from the space charge around the cathode to anode despite
grid voltage's supposed control of current.

One simply cannot deny that a huge anode feedback effect exists,
and where you have a grid also able to control the Ia
with a gm of about 5mA/V then there MUST be a summing of the anode and grid voltage effects
according to some formula ( upon which Professor Child throws more light than I do ) .

So its very easy to see that NFB is alive and operational in a triode.


[snip]

I am not a qualified university educated triodologist.

But my powers of observation reveal NFB in triodes to me.

But by exactly what process in purely technical terms would you use to
allege NFB does NOT exist in triodes?


Patrick, you're simply being stubborn at this point. We have pointed
out, over and over, that a plate resistance, which, so far, you CANNOT
and HAVE NOT proven does not exist, can account for all of the "feedback
effects," by which you mean damping, that you talk about.



The Ea / Ia at the quiecent state = 5,700 ohms for the 300B I mentioned.
But why does it measure 800 ohms when small variations in Ea are made?


Because the *model* of a triode includes a voltage offset in series with
a diode, caused by the grid. Given, say, -10 Vg, you will get no
positive current until you reach a certain plate voltage, enough to
overcome the voltage offset caused by the grid. Specifically, the grid
can repel the electrons until the plate voltage more or less equals the
grid voltage times mu. You get no negative current because a triode only
conducts one way, like a diode.

Similarly, if you have two resistors in series, with a battery between
them, you get no positive current when placing a voltage after the
second resistor until its voltage equals the battery placed between the
two resistors. A triode acts like a resistor with a voltage offset which
is controlled by the grid.

if there was no FB and the tube was just a purely passive device like a resistor,
the changes in Ea would give Ra = 5,700 ohms.
but we get 800 ohms.
How come?

See above.

Yes, in the
absence of tests which possibly can distinguish between anode resistance
and triode feedback, we really don't know which it is. But to claim that
feedback must exist *because* effects equivalent to either feedback or
low plate resistance exist is unscientific. You have a choice, and that
is why the rest of us simply state that, in the absence of any logical,
intellectual, or engineering advantage for feedback, we prefer low plate
resistance as a *model*. That's our choice. Maybe the other choice is
better. But you have not given any analysis to my knowledge which proves
that such a choice does not exist, or even that a feedback model is a
better choice for audio or electronics.



You call me stubborn, and refuse to proove I'm wrong, and you cannot deal with the idea
of the mutual effect of the two changing voltages of grid and anode which BOTH
have large effects on the Ia and so who is right?
If say I am wrong, then so is Prfessor Child, and all the guys with
better minds than yours or mine.


I call you stubborn because you claim that feedback exists, when an
alternative model explains everything (admittedly, as far I know) just
as well. To say that it *might* be feedback would be okay, but until you
have proofs or experiments that rule out the resistor model, you cannot
say definitively that triodes have feedback. The plate may simply pull
electrons along in exactly the same manner as a battery pulls electrons
through an ordinary resistor. Then again, perhaps it would be *best*
described as feedback, and I can easily admit that. However, Henry has
some very convincing lines of reasoning that show no advantage or
greater accuracy or anything like that for feedback, I have not been
able to find lines of reasoning to contradict him, and again, as far as
I know, neither have you! I don't have to prove that triodes do not have
feedback to "prove you wrong," when all I am trying to claim is that you
are not necessarily right!

Let me see if I can make this clear. Let's assume, for a moment, that a
test will appear that truly can distinguish between low impedances
caused by feedback, and low impedances caused by a low impedance, a
simple resistance. I do not know for certain what that test would tell
us about triodes. As far as I can tell, neither do you. THAT appears to
me to be the honest answer! Since resistor models are less complicated
than feedback models, I understandably believe that everyone should use
the simpler model until it is proven to be a less accurate description,
since humans make fewer errors when using simpler, but equally powerful,
models. The MOMENT someone proves that feedback is the more accurate
model, I will state, publicly, that you were right, and that unless we
are working in some situation where there is no significant difference
between the two models, we should use feedback to describe triodes. But
not until then!

And honestly, Patrick, do you not agree that if triodes have feedback,
then so do resistors? Batteries affect the electric field surrounding
the atoms in resistors, and increasing the voltage increases the field
strength, just as it does in triodes and diodes, and if it weren't for
that, the resistance would be much higher, perhaps infinite. Mind you,
resistors might indeed have feedback, but until we find situations that
require us to view them in such a manner, why on Earth would we want to
replace the much simpler resistor model for resistors with a feedback
model? And the same question applies to triodes and diodes.

Where is you alternative modelling?


We have stated it over and over and over again -- well, we've stated the
resistor part, perhaps the battery part was not stated as clearly as it
should have been -- I don't know how many times we are supposed to
repeat ourselves.

I see there is NFB in a triode not because I am stubborn, but because
it hits me in the eye as being so very obvious, and its missing from
all other devices.


Yes, it appears to be feedback to you. It appears to be a resistance in
series with a voltage to everyone else. Who is right? Until we have
better proofs than anyone has presented, on either side, that "the other
side's model" cannot fully account for a triode's behavior, we do not
know which one is truly correct, and therefore should use the simpler
model, and that is the resistance model.

Phil

Patrick Turner.




Phil





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"Patrick Turner" wrote in message ...
[Yada, yada, yada]


Whatever. I've wasted enough of my time on you, Patrick.

-Henry


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Patrick Turner Patrick Turner is offline
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Phil wrote:

Patrick Turner wrote:


Phil wrote:


Patrick Turner wrote:

[snip]


Professor child called the mutual effect of anode AND grid voltages
in a triode a form of "self regulation".
See Radio Engineering, by Terman, 1937.

He does not call it NFB probably because it would have confused ppl at the time
who were used to NFB ONLY being some external networking to
get an amp of device to display lower Ra thd etc than otherwise it would
without NFB.

The observation of a triode as a mystery 3 terminal device could be
argued to contain NFB.

When you have a 300B with Ia = 70mA, Ea = +400V,
then if it acted like a resistor without NFB the R value
would be 400 / 0.07 = 5,700 ohms.
But where one maintains the grid bias voltage and fixes the cathode voltage,
abd simply raises the anode voltage by say 80V,
then one soon finds that the Ia change = 100mA, and
it is because the Ra = 800 ohms, and not the 5,700 ohms of quiescent Ea / Ia .
How can this be? Its because the anode has a massive effect on the
flow of electrons from the space charge around the cathode to anode despite
grid voltage's supposed control of current.

One simply cannot deny that a huge anode feedback effect exists,
and where you have a grid also able to control the Ia
with a gm of about 5mA/V then there MUST be a summing of the anode and grid voltage effects
according to some formula ( upon which Professor Child throws more light than I do ) .

So its very easy to see that NFB is alive and operational in a triode.

[snip]

I am not a qualified university educated triodologist.

But my powers of observation reveal NFB in triodes to me.

But by exactly what process in purely technical terms would you use to
allege NFB does NOT exist in triodes?

Patrick, you're simply being stubborn at this point. We have pointed
out, over and over, that a plate resistance, which, so far, you CANNOT
and HAVE NOT proven does not exist, can account for all of the "feedback
effects," by which you mean damping, that you talk about.



The Ea / Ia at the quiecent state = 5,700 ohms for the 300B I mentioned.
But why does it measure 800 ohms when small variations in Ea are made?


Because the *model* of a triode includes a voltage offset in series with
a diode, caused by the grid. Given, say, -10 Vg, you will get no
positive current until you reach a certain plate voltage, enough to
overcome the voltage offset caused by the grid. Specifically, the grid
can repel the electrons until the plate voltage more or less equals the
grid voltage times mu. You get no negative current because a triode only
conducts one way, like a diode.

Similarly, if you have two resistors in series, with a battery between
them, you get no positive current when placing a voltage after the
second resistor until its voltage equals the battery placed between the
two resistors. A triode acts like a resistor with a voltage offset which
is controlled by the grid.


All you are doing like nearly everyone else is denying the summing NFB interactive
effects of anode voltage AND grid voltage upon Ia, and saying
the triode is merely a model of a battery or low Z voltage gene in series with a diode
or resistor which is equivalent to Ra.
A triode becomes like a diode when its grid is tied to the cathode or at a fixed voltage
in reference to the cathode; then there is no Vg-k variation, and no FB either,
because TWO voltage changes are required to make the loop for FB to occur.

We already know all the triode models are true, but true because of the NFB.

In a pentode there is also a battery or low Z voltage gene producing
µ x Eg and with an R in series which is equivalent to Ra.
In a pentode, µ = gm x Ra and without the NFB,
and for a 6AU6 µ approx = 0.0045A/V x 1,500,000 ohms = 6,750 at 7.6mA.

We can IMAGINE that the 6AU6 is a voltage gene with an output of
6,6750V for 1V input from a grid, and then
we have Ra as a series R = 1.5M and say we have a load of 20k then the current in the Ra + 20k
is 6,750V / ( 1.5M + 20k ) = 4.44mA and so the load voltage = 20 x 4.44 = 89V.

Thus the tube has a gain of 89.

If the load is altered and voltage readings taken then one can deduce Ra = 1.5M

If the anode voltage is altered by a low Z voltage source we find
Ra = 1.5M although Ea / Ia = 200V / 0.0076A = 26.3k, so how come
we measure the Ra at 1.5M?
Its because there is VIRTUALLY NO NFB, the opposite case to a triode.

If we connect the screen to anode, and triodise the 6AU6,
then the anode voltage is allowed to affect the Ia and
the apparent Ra drops because the µ drops from 6,750 to 36 due to NFB
and the Ra = µ / gm = 36 / 0.0048 = 7,500ohms, so the NFB has a large
effect on reducing Ra.

What other mechanism do you suggest causes Ra to be so reduced?

Then we should consider the case of a triode where there is NO ANODE CURRENT
CHANGE IN THE OPERATION.

This is where there is a CCS load, and no anode current occurs.

The summed effect of the grid and anode voltage upon the space charge
remains.
NO anode current change is possible because of the infinite resistance of the load.
The NFB effect is maximal and voltage gain = triode µ.
Witha 6AU6 pentode with CCS, the µ = gain and would be 6,750 because
there is a very small VOLTAGE caused NFB effect.

How does one explain the tube working with CCS load without thinking of the
amounts of local NFB????





if there was no FB and the tube was just a purely passive device like a resistor,
the changes in Ea would give Ra = 5,700 ohms.
but we get 800 ohms.
How come?

See above.


You don't explain it.



Yes, in the
absence of tests which possibly can distinguish between anode resistance
and triode feedback, we really don't know which it is. But to claim that
feedback must exist *because* effects equivalent to either feedback or
low plate resistance exist is unscientific. You have a choice, and that
is why the rest of us simply state that, in the absence of any logical,
intellectual, or engineering advantage for feedback, we prefer low plate
resistance as a *model*. That's our choice. Maybe the other choice is
better. But you have not given any analysis to my knowledge which proves
that such a choice does not exist, or even that a feedback model is a
better choice for audio or electronics.



You call me stubborn, and refuse to proove I'm wrong, and you cannot deal with the idea
of the mutual effect of the two changing voltages of grid and anode which BOTH
have large effects on the Ia and so who is right?
If say I am wrong, then so is Prfessor Child, and all the guys with
better minds than yours or mine.


I call you stubborn because you claim that feedback exists, when an
alternative model explains everything (admittedly, as far I know) just
as well.


I won't call you stubborn.

The "alternative models" of a triode have been known by many for
70 years and are explained at my website and we agree
on the models of battery/voltage gene with series R to represent Ra.

But you still fail to see the NFB that exists.

The models of generator + Ra resistance DO NOT explain or even include the NFB
effects, but are the models of the tube working AFTER TAKING INTO ACCOUNT WHATEVER NFB EXISTS.


To say that it *might* be feedback would be okay, but until you
have proofs or experiments that rule out the resistor model, you cannot
say definitively that triodes have feedback.


I leave you to consider that minds better than yours have concluded
there is NFB within a triode.

The plate may simply pull

electrons along in exactly the same manner as a battery pulls electrons
through an ordinary resistor.


No such pull along effect occurs in resistors.

A resistor works in an entirely different manner to any tube.

Then again, perhaps it would be *best*
described as feedback, and I can easily admit that.


The NFB is only evident when one considers the COMBINED NET EFFECT
OF TWO VOLTAGES within the tube, ie, grid and anode voltages.

However, Henry has
some very convincing lines of reasoning that show no advantage or
greater accuracy or anything like that for feedback, I have not been
able to find lines of reasoning to contradict him, and again, as far as
I know, neither have you! I don't have to prove that triodes do not have
feedback to "prove you wrong," when all I am trying to claim is that you
are not necessarily right!


Try reading a few more books about triodes rather than seeking some
NFB de-bunking premise from Henry.
With all due respsect to Henry, he ain't the world's authority on vacuum tube theory.
Nor am I. So read up elsewhere. Until you have read a lot more, consider yourself ignorant,
because that would be a fact.





Let me see if I can make this clear. Let's assume, for a moment, that a
test will appear that truly can distinguish between low impedances
caused by feedback, and low impedances caused by a low impedance, a
simple resistance.


Resistances can be any value, and characterized by being a fixed value for a
large range of currents and frequencies.

I do not know for certain what that test would tell
us about triodes. As far as I can tell, neither do you.


Well you are not able to hear or see what I have been saying.
You don't want to accept you are mostv likely to be wrong, and ignorant.
You have read almost nothing, have not benefitted from education,
and are at a similar position of where you might think you know your stomach's anatomy
by gazing at your navel.



THAT appears to
me to be the honest answer! Since resistor models are less complicated
than feedback models, I understandably believe that everyone should use
the simpler model until it is proven to be a less accurate description,
since humans make fewer errors when using simpler, but equally powerful,
models.


The simple models INCLUDES THE NFB AND USES VALUES FOR RA
which exist because of the NFB.

The models DON'T EXPLAIN OR INCLUDE THE NFB MODELS.

The models were invented TO BE A SIMPLIFIED TOOL for design purposes.

The MOMENT someone proves that feedback is the more accurate
model, I will state, publicly, that you were right, and that unless we
are working in some situation where there is no significant difference
between the two models, we should use feedback to describe triodes. But
not until then!

And honestly, Patrick, do you not agree that if triodes have feedback,
then so do resistors?


Resistors have no NFB in the same way pigs don't have wings and cannot fly.

Triodes do have NFB because there is an interactive voltage summing of two electrodes
which act upon the space charge.

I ask you to consider not making yourself look any more ignorant than you appear to be by likening

resistors to vacuum tubes in any way.

Batteries affect the electric field surrounding
the atoms in resistors, and increasing the voltage increases the field
strength, just as it does in triodes and diodes, and if it weren't for
that, the resistance would be much higher, perhaps infinite.


Huh?

This is a weird statement and I suggest you consult a professor of electronics
to guide you arrange words with more meaning.

maybe he'll give you a reading list if you decide to attend his classes at a university.

The exams they set at the end of such courses exist to guage whether or not
you understand what was in the books you may have read.



Mind you,
resistors might indeed have feedback, but until we find situations that
require us to view them in such a manner, why on Earth would we want to
replace the much simpler resistor model for resistors with a feedback
model? And the same question applies to triodes and diodes.


I suggest you don't know if there is or isn't NFB in resistances.
Find out for sure, will you, and let us know what you think and why.

You need to know, to understand.





Where is you alternative modelling?


We have stated it over and over and over again -- well, we've stated the
resistor part, perhaps the battery part was not stated as clearly as it
should have been -- I don't know how many times we are supposed to
repeat ourselves.


We agree on the models, but the models includes the NFB in operation.

The NFB loop elements are not included in the model because they were designed
to allow simple circuit analysis.

The triode model is low µ generator and low Ra series resistance, lots of local NFB.
The pentode model has high µ gene and high Ra series R, and very little NFB.

The model of a vacuum tube as a battery with series R is only correct for
DC operartion and is severly limited in its usefulness in applications
and the AC model with the battery being replaced with a generator
of low Z output resistance whose output = µ x Vg is the accurate model and useful
for both DC and AC operation.

Unless you understand the operation of the vacuum tube as AC generator with series R for Ra,
or else constant current generator = gm x Vg shunted by resistance = Ra then
your mind is severly limited for any exercize involving making up circuitry where
the current flows can be very basically examined.




I see there is NFB in a triode not because I am stubborn, but because
it hits me in the eye as being so very obvious, and its missing from
all other devices.


Yes, it appears to be feedback to you. It appears to be a resistance in
series with a voltage to everyone else.


There are many more ppl than myself who believe in the NFB withing vacuum tubes.

The model of resistance in series with battery or low Z voltage gene has been known for
70 years as a basic tool, and includes the effects of whatever NFB exists.

Because you cannot see the NFB, you say it cannot exist.

I say that not only is there NFB within vacuum tubes, but also that you are ignorant,
and in need of a serious increase in your education and you must forthwith
proceed without delay to a nice large pile of books wherin you may find answers
you are not getting from me.

Until you have read the books, and proved you understand what you have read, you
remain someone who is guessing his way through life, unguided by any real knowledge.

Patrick Turner.



Who is right? Until we have
better proofs than anyone has presented, on either side, that "the other
side's model" cannot fully account for a triode's behavior, we do not
know which one is truly correct, and therefore should use the simpler
model, and that is the resistance model.

Phil

Patrick Turner.




Phil




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Henry Pasternack Henry Pasternack is offline
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Default Explanation still required for triode superiority

"Patrick Turner" wrote in message ...
A triode becomes like a diode when its grid is tied to the cathode or at a fixed
voltage in reference to the cathode; then there is no Vg-k variation, and no FB
either, because TWO voltage changes are required to make the loop for FB to
occur.


Three days ago, you wrote:

The observation of a triode as a mystery 3 terminal device could be argued
to contain NFB.

But where one maintains the grid bias voltage and fixes the cathode voltage,
and simply raises the anode voltage by say 80V, then one soon finds that
the Ia change = 100mA, and it is because the Ra = 800 ohms, and not the
5,700 ohms of quiescent Ea / Ia . How can this be? Its because the anode
has a massive effect on the flow of electrons from the space charge around
the cathode to anode despite grid voltage's supposed control of current.


Hah. Gotcha there.

-Henry


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Phil Phil is offline
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Default Explanation still required for triode superiority

Patrick Turner wrote:

Phil wrote:


Patrick Turner wrote:


Phil wrote:



Patrick Turner wrote:

[snip]



Professor child called the mutual effect of anode AND grid voltages
in a triode a form of "self regulation".
See Radio Engineering, by Terman, 1937.

He does not call it NFB probably because it would have confused ppl at the time
who were used to NFB ONLY being some external networking to
get an amp of device to display lower Ra thd etc than otherwise it would
without NFB.

The observation of a triode as a mystery 3 terminal device could be
argued to contain NFB.

When you have a 300B with Ia = 70mA, Ea = +400V,
then if it acted like a resistor without NFB the R value
would be 400 / 0.07 = 5,700 ohms.
But where one maintains the grid bias voltage and fixes the cathode voltage,
abd simply raises the anode voltage by say 80V,
then one soon finds that the Ia change = 100mA, and
it is because the Ra = 800 ohms, and not the 5,700 ohms of quiescent Ea / Ia .
How can this be? Its because the anode has a massive effect on the
flow of electrons from the space charge around the cathode to anode despite
grid voltage's supposed control of current.

One simply cannot deny that a huge anode feedback effect exists,
and where you have a grid also able to control the Ia
with a gm of about 5mA/V then there MUST be a summing of the anode and grid voltage effects
according to some formula ( upon which Professor Child throws more light than I do ) .

So its very easy to see that NFB is alive and operational in a triode.

[snip]


I am not a qualified university educated triodologist.

But my powers of observation reveal NFB in triodes to me.

But by exactly what process in purely technical terms would you use to
allege NFB does NOT exist in triodes?

Patrick, you're simply being stubborn at this point. We have pointed
out, over and over, that a plate resistance, which, so far, you CANNOT
and HAVE NOT proven does not exist, can account for all of the "feedback
effects," by which you mean damping, that you talk about.


The Ea / Ia at the quiecent state = 5,700 ohms for the 300B I mentioned.
But why does it measure 800 ohms when small variations in Ea are made?


Because the *model* of a triode includes a voltage offset in series with
a diode, caused by the grid. Given, say, -10 Vg, you will get no
positive current until you reach a certain plate voltage, enough to
overcome the voltage offset caused by the grid. Specifically, the grid
can repel the electrons until the plate voltage more or less equals the
grid voltage times mu. You get no negative current because a triode only
conducts one way, like a diode.

Similarly, if you have two resistors in series, with a battery between
them, you get no positive current when placing a voltage after the
second resistor until its voltage equals the battery placed between the
two resistors. A triode acts like a resistor with a voltage offset which
is controlled by the grid.



All you are doing like nearly everyone else is denying the summing NFB interactive
effects of anode voltage AND grid voltage upon Ia, and saying
the triode is merely a model of a battery or low Z voltage gene in series with a diode
or resistor which is equivalent to Ra.


Oh for god's sake WOULD YOU WAKE UP!!! For the umpteenth time, the fact
that some theory fits the known facts regarding the dinosaur's demise
DOES NOT MAKE THAT THEORY TRUE! Patrick, no one is denying that you
could have a summing effect from plate and grid voltages, and I'm
getting tired of you telling me "you don't believe X" when I have told
you, over and over, that I have no evidence that X isn't true. For the
umpteenth time, the fact that your feedback theory can explain things
does not, and will not ever, BY ITSELF prove that it is true! Why is
this so difficult for you to understand? What references or experiments
did you perform that PROVED that increasing the voltage across a triode
does not simply pull more electrons past all the obstacles in a triode,
in exactly the same way that increasing the voltage across a resistor
pulls more electrons past the thermally agitated atoms? When did you
PROVE that a simple resistance mechanism does NOT exist in a triode? Did
you never prove that? Then you cannot rule it out as a possible
explanation, period. Basic reasoning 101. Duh. And please, please don't
try to tell me that because your theory fits, therefore all other
theories are "proven" wrong (see dinosaur example above).

A triode becomes like a diode when its grid is tied to the cathode or at a fixed voltage
in reference to the cathode; then there is no Vg-k variation, and no FB either,
because TWO voltage changes are required to make the loop for FB to occur.


What??? You know, up to now, I've thought your feedback model had real
merit, and I also thought you straightened out your thoughts on the
diode/triode issues, so let's get this straight. If I tie the grid to
the cathode, and increase the voltage across the tube, I soon get a
current of 100 mA and a dynamic resistance of, say, 600 ohms. But
there's no feedback here, according to you. If I tie the grid at -50 Vg,
and repeat until I reach 100 mA, I again find a dynamic resistance of
600 ohms. And again, according to you, there's no feedback??? But now,
if I put in an audio signal, but measure the dynamic resistance, I find
that it's 600 ohms, again, at around 100 mA, but NOW there's feedback???

Patrick, the whole point about the difference between triodes and
pentodes or transistors is that, given a *fixed* grid voltage, changing
the voltage across the tube causes a large change in current. It has a
low output resistance. When the speaker tries to change its voltage due
to stored energy, the triode resists this, even if the grid voltage
happens to be constant at that time. Now, you can say that the change in
plate voltage changes the flow of electrons to the plate in the SAME WAY
as changing the grid voltage, which would be a feedback model. Or, you
can say that a triode fails to isolate a basic resistance mechanism
which exists in triodes and pentodes -- where increasing the plate or
screen voltage draws more current through the spaces between the grid
wires, just as increasing the voltage across a resistor draws more
current through the atoms -- from the plate voltage. In other words, the
screen *isolates* the inherent resistance from changes in plate voltage,
which would be a resistance model. So far, so good, but if you think
your feedback model requires feedback to "mystically" disappear every
time the grid voltage happens to be held steady, then you need to
abandon your feedback model, because that's clearly stupid. Mind you,
*I* won't abandon your feedback model, because I know that it does apply
to diodes, resistors, and triodes with constant grid voltages, and I can
accept that. But then, neither do I assume that such a weird model is
true merely because it, like other models, happens to fit the facts.

We already know all the triode models are true, but true because of the NFB.


A claim, backed up by nothing but faulty arguments (meaning you have no
proof).

In a pentode there is also a battery or low Z voltage gene producing
µ x Eg and with an R in series which is equivalent to Ra.
In a pentode, µ = gm x Ra and without the NFB,
and for a 6AU6 µ approx = 0.0045A/V x 1,500,000 ohms = 6,750 at 7.6mA.

We can IMAGINE that the 6AU6 is a voltage gene with an output of
6,6750V for 1V input from a grid, and then
we have Ra as a series R = 1.5M and say we have a load of 20k then the current in the Ra + 20k
is 6,750V / ( 1.5M + 20k ) = 4.44mA and so the load voltage = 20 x 4.44 = 89V.

Thus the tube has a gain of 89.

If the load is altered and voltage readings taken then one can deduce Ra = 1.5M

If the anode voltage is altered by a low Z voltage source we find
Ra = 1.5M although Ea / Ia = 200V / 0.0076A = 26.3k, so how come
we measure the Ra at 1.5M?
Its because there is VIRTUALLY NO NFB, the opposite case to a triode.


Or because the pentode shields its inherent low resistance -- and if you
change the screen voltage, you will quickly see that such a low
resistance exists -- from changes in plate voltage. Reasoning 101, the
presence of one possible explanation DOES NOT PRECLUDE other possible
explanations. The existence of the phlogiston theory of combustion did
not prove that the Lavosier's oxygen theory of combustion was false.

If we connect the screen to anode, and triodise the 6AU6,
then the anode voltage is allowed to affect the Ia and
the apparent Ra drops because the µ drops from 6,750 to 36 due to NFB


OR because you are no longer shielding the low resistance from changes
in plate voltage. Tell me again, what does the NFB model achieve that
the low resistance model does not?

and the Ra = µ / gm = 36 / 0.0048 = 7,500ohms, so the NFB has a large
effect on reducing Ra.

What other mechanism do you suggest causes Ra to be so reduced?


The existence of a shield/screen that prevents changes in plate voltage
from accessing the low internal resistance, just as we have said (in so
many words) all along.

Then we should consider the case of a triode where there is NO ANODE CURRENT
CHANGE IN THE OPERATION.


Okay, I'll bite. Who knows? Maybe you'll actually prove that NFB is
indeed the preferred explanation.

This is where there is a CCS load, and no anode current occurs.


No changes in plate current. Got it.

The summed effect of the grid and anode voltage upon the space charge
remains.


So? In other words, we can continue to view this situation using the NFB
model. Fine, that means that it has not so far been proven false. That
fact tells us NOTHING about the resistance model.

NO anode current change is possible because of the infinite resistance of the load.


True.

The NFB effect is maximal and voltage gain = triode µ.


Whatever (but Av = u, true).

Witha 6AU6 pentode with CCS, the µ = gain and would be 6,750 because
there is a very small VOLTAGE caused NFB effect.


Or, the resistance is not completely shielded from the plate voltage,
preventing u from being infinite. True.

How does one explain the tube working with CCS load without thinking of the
amounts of local NFB????


What's your point? In both cases, the grid-cathode voltage MUST change
if you are to change the plate-cathode voltage, although you need to
change it less with a pentode. So? With an unshielded resistance, the
grid-cathode voltage must change more to compensate for that unshielded
resistance. So? That's just another viewpoint of the same low plate
resistance of a triode.




if there was no FB and the tube was just a purely passive device like a resistor,
the changes in Ea would give Ra = 5,700 ohms.
but we get 800 ohms.
How come?


See above.



You don't explain it.


I did explain it, you merely didn't understand it (which might not be
your fault). The voltage in series with a resistance model means that
you get no current at all until Vp is approximately mu x Vg, at which
point the 800 ohm resistance comes into play. That's the model, and it
correctly describes triode behavior.


Yes, in the
absence of tests which possibly can distinguish between anode resistance
and triode feedback, we really don't know which it is. But to claim that
feedback must exist *because* effects equivalent to either feedback or
low plate resistance exist is unscientific. You have a choice, and that
is why the rest of us simply state that, in the absence of any logical,
intellectual, or engineering advantage for feedback, we prefer low plate
resistance as a *model*. That's our choice. Maybe the other choice is
better. But you have not given any analysis to my knowledge which proves
that such a choice does not exist, or even that a feedback model is a
better choice for audio or electronics.


You call me stubborn, and refuse to proove I'm wrong, and you cannot deal with the idea
of the mutual effect of the two changing voltages of grid and anode which BOTH
have large effects on the Ia and so who is right?
If say I am wrong, then so is Prfessor Child, and all the guys with
better minds than yours or mine.


I call you stubborn because you claim that feedback exists, when an
alternative model explains everything (admittedly, as far I know) just
as well.



I won't call you stubborn.

The "alternative models" of a triode have been known by many for
70 years and are explained at my website and we agree
on the models of battery/voltage gene with series R to represent Ra.

But you still fail to see the NFB that exists.


Be fair and accurate here; I still fail to see a PROOF that NFB
correctly describes a triode, while resistance (plus a voltage) does not.

The models of generator + Ra resistance DO NOT explain or even include the NFB
effects, but are the models of the tube working AFTER TAKING INTO ACCOUNT WHATEVER NFB EXISTS.


I have no idea what your point is here.


To say that it *might* be feedback would be okay, but until you
have proofs or experiments that rule out the resistor model, you cannot
say definitively that triodes have feedback.



I leave you to consider that minds better than yours have concluded
there is NFB within a triode.


That is merely an argument, an indication method, not a proof. By the
way, which better minds are you thinking of?

The plate may simply pull


electrons along in exactly the same manner as a battery pulls electrons
through an ordinary resistor.



No such pull along effect occurs in resistors.


Oh really? Pray tell how a resistor does work.

A resistor works in an entirely different manner to any tube.


Which would be ...


Then again, perhaps it would be *best*
described as feedback, and I can easily admit that.



The NFB is only evident when one considers the COMBINED NET EFFECT
OF TWO VOLTAGES within the tube, ie, grid and anode voltages.


Ridiculous, the low impedance of a triode is quite intact when the grid
voltage is fixed. Furthermore, simply remove the grid from a triode
(there are several rectifiers where this was done), and I guarantee that
the dynamic resistance for a given plate voltage will be about the same
as in the triode version when the grid is tied to ground, and yet you're
claiming that the diode version does not have feedback, and therefore
should have a much higher resistance. Select equal current levels for
the diode version and the triode version using several fixed values for
the grid voltage, and you still get equal dynamic resistances. Put an
audio signal in, and measure the dynamic resistance at some moment in
time, you will still get the same values for a given current level. If a
triode has feedback, then a diode has feedback. That is NOT enough to
make me abandon the NFB model -- although it gave me pause for a while
-- why should you feel it's necessary to DENY that a diode has the same
feedback mechanism you claim exists for triodes?


However, Henry has
some very convincing lines of reasoning that show no advantage or
greater accuracy or anything like that for feedback, I have not been
able to find lines of reasoning to contradict him, and again, as far as
I know, neither have you! I don't have to prove that triodes do not have
feedback to "prove you wrong," when all I am trying to claim is that you
are not necessarily right!



Try reading a few more books about triodes rather than seeking some
NFB de-bunking premise from Henry.
With all due respsect to Henry, he ain't the world's authority on vacuum tube theory.


He could be the devil himself, but that's irrelevant, along with his
knowledge, when it comes to the quality of his arguments on this matter.
You don't "disprove" a theory by saying the author is stupid or evil.
You ignore the characteristics of the author altogether, and focus on
the accuracy, or lack thereof, of the theory itself. Reasoning 101.

Nor am I. So read up elsewhere. Until you have read a lot more, consider yourself ignorant,
because that would be a fact.


A general criticism without any support or examples. An old debating
trick. Useless ...


Let me see if I can make this clear. Let's assume, for a moment, that a
test will appear that truly can distinguish between low impedances
caused by feedback, and low impedances caused by a low impedance, a
simple resistance.



Resistances can be any value, and characterized by being a fixed value for a
large range of currents and frequencies.


The point was to assume, to hypothesize, that a test capable of
distinguishing between a NFB model and a resistance model exists. Given
that hypothesis ...


I do not know for certain what that test would tell
us about triodes. As far as I can tell, neither do you.



Well you are not able to hear or see what I have been saying.


That would indeed be one explanation. Another would be just the reverse,
that you insist on ignoring the fact that without a proof that one model
is correct, and the other model incorrect, you cannot justifiably claim
that the low output impedance of triodes is definitely due to a feedback
mechanism.

You don't want to accept you are mostv likely to be wrong, and ignorant.


That put-down doesn't necessarily follow from facts; it's just another
unsupported criticism, and therefore useless.

You have read almost nothing, have not benefitted from education,
and are at a similar position of where you might think you know your stomach's anatomy
by gazing at your navel.

**** you, Patrick. You know, every once in a while I think that Ian is
right; you're a bully. Or at the very least, you act like one. Let me
get this straight. I'm just a stupid **** because I don't believe you
have proven your case? Let's see if I can put this in a manner you can
understand: **** YOU PATRICK!!! Take your pet, unsupported, unproven
theories, and shove them up your ass. If you can't discuss this matter
in an adult, intelligent, honest manner, than I have no further use for
you. Go use your bullying techniques on someone else. I'm not impressed.
Henry was right, I've wasted all the time on you I need to. Goodbye.

Phil




THAT appears to
me to be the honest answer! Since resistor models are less complicated
than feedback models, I understandably believe that everyone should use
the simpler model until it is proven to be a less accurate description,
since humans make fewer errors when using simpler, but equally powerful,
models.



The simple models INCLUDES THE NFB AND USES VALUES FOR RA
which exist because of the NFB.

The models DON'T EXPLAIN OR INCLUDE THE NFB MODELS.

The models were invented TO BE A SIMPLIFIED TOOL for design purposes.


The MOMENT someone proves that feedback is the more accurate
model, I will state, publicly, that you were right, and that unless we
are working in some situation where there is no significant difference
between the two models, we should use feedback to describe triodes. But
not until then!

And honestly, Patrick, do you not agree that if triodes have feedback,
then so do resistors?



Resistors have no NFB in the same way pigs don't have wings and cannot fly.

Triodes do have NFB because there is an interactive voltage summing of two electrodes
which act upon the space charge.

I ask you to consider not making yourself look any more ignorant than you appear to be by likening

resistors to vacuum tubes in any way.


Batteries affect the electric field surrounding
the atoms in resistors, and increasing the voltage increases the field
strength, just as it does in triodes and diodes, and if it weren't for
that, the resistance would be much higher, perhaps infinite.



Huh?

This is a weird statement and I suggest you consult a professor of electronics
to guide you arrange words with more meaning.

maybe he'll give you a reading list if you decide to attend his classes at a university.

The exams they set at the end of such courses exist to guage whether or not
you understand what was in the books you may have read.




Mind you,
resistors might indeed have feedback, but until we find situations that
require us to view them in such a manner, why on Earth would we want to
replace the much simpler resistor model for resistors with a feedback
model? And the same question applies to triodes and diodes.



I suggest you don't know if there is or isn't NFB in resistances.
Find out for sure, will you, and let us know what you think and why.

You need to know, to understand.




Where is you alternative modelling?


We have stated it over and over and over again -- well, we've stated the
resistor part, perhaps the battery part was not stated as clearly as it
should have been -- I don't know how many times we are supposed to
repeat ourselves.



We agree on the models, but the models includes the NFB in operation.

The NFB loop elements are not included in the model because they were designed
to allow simple circuit analysis.

The triode model is low µ generator and low Ra series resistance, lots of local NFB.
The pentode model has high µ gene and high Ra series R, and very little NFB.

The model of a vacuum tube as a battery with series R is only correct for
DC operartion and is severly limited in its usefulness in applications
and the AC model with the battery being replaced with a generator
of low Z output resistance whose output = µ x Vg is the accurate model and useful
for both DC and AC operation.

Unless you understand the operation of the vacuum tube as AC generator with series R for Ra,
or else constant current generator = gm x Vg shunted by resistance = Ra then
your mind is severly limited for any exercize involving making up circuitry where
the current flows can be very basically examined.



I see there is NFB in a triode not because I am stubborn, but because
it hits me in the eye as being so very obvious, and its missing from
all other devices.


Yes, it appears to be feedback to you. It appears to be a resistance in
series with a voltage to everyone else.



There are many more ppl than myself who believe in the NFB withing vacuum tubes.

The model of resistance in series with battery or low Z voltage gene has been known for
70 years as a basic tool, and includes the effects of whatever NFB exists.

Because you cannot see the NFB, you say it cannot exist.

I say that not only is there NFB within vacuum tubes, but also that you are ignorant,
and in need of a serious increase in your education and you must forthwith
proceed without delay to a nice large pile of books wherin you may find answers
you are not getting from me.

Until you have read the books, and proved you understand what you have read, you
remain someone who is guessing his way through life, unguided by any real knowledge.

Patrick Turner.




Who is right? Until we have
better proofs than anyone has presented, on either side, that "the other
side's model" cannot fully account for a triode's behavior, we do not
know which one is truly correct, and therefore should use the simpler
model, and that is the resistance model.

Phil

Patrick Turner.




Phil



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Patrick Turner Patrick Turner is offline
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Default Explanation still required for triode superiority



Henry Pasternack wrote:

"Patrick Turner" wrote in message ...
A triode becomes like a diode when its grid is tied to the cathode or at a fixed
voltage in reference to the cathode; then there is no Vg-k variation, and no FB
either, because TWO voltage changes are required to make the loop for FB to
occur.


Three days ago, you wrote:

The observation of a triode as a mystery 3 terminal device could be argued
to contain NFB.

But where one maintains the grid bias voltage and fixes the cathode voltage,
and simply raises the anode voltage by say 80V, then one soon finds that
the Ia change = 100mA, and it is because the Ra = 800 ohms, and not the
5,700 ohms of quiescent Ea / Ia . How can this be? Its because the anode
has a massive effect on the flow of electrons from the space charge around
the cathode to anode despite grid voltage's supposed control of current.


Hah. Gotcha there.

-Henry


Nobody is arguing that a triode with its grid tied to its cathode is anything different
to a diode in its behaviour.

But as soon as you have active control of the ia or Ea by means of altering the
Eg to Ek voltage, then the tube is anything but a diode and a NFB effect operates.

The NFB is the summed effect of the two applied voltages of anode and grid
with respect to cathode.

Got me where?

You'll have to try harder my friend to corner me on NFB.

Patrick Turner.




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Patrick Turner Patrick Turner is offline
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Default Explanation still required for triode superiority



Phil wrote:

Patrick Turner wrote:

Phil wrote:


Patrick Turner wrote:


Phil wrote:



Patrick Turner wrote:

[snip]



Professor child called the mutual effect of anode AND grid voltages
in a triode a form of "self regulation".
See Radio Engineering, by Terman, 1937.

He does not call it NFB probably because it would have confused ppl at the time
who were used to NFB ONLY being some external networking to
get an amp of device to display lower Ra thd etc than otherwise it would
without NFB.

The observation of a triode as a mystery 3 terminal device could be
argued to contain NFB.

When you have a 300B with Ia = 70mA, Ea = +400V,
then if it acted like a resistor without NFB the R value
would be 400 / 0.07 = 5,700 ohms.
But where one maintains the grid bias voltage and fixes the cathode voltage,
abd simply raises the anode voltage by say 80V,
then one soon finds that the Ia change = 100mA, and
it is because the Ra = 800 ohms, and not the 5,700 ohms of quiescent Ea / Ia .
How can this be? Its because the anode has a massive effect on the
flow of electrons from the space charge around the cathode to anode despite
grid voltage's supposed control of current.

One simply cannot deny that a huge anode feedback effect exists,
and where you have a grid also able to control the Ia
with a gm of about 5mA/V then there MUST be a summing of the anode and grid voltage effects
according to some formula ( upon which Professor Child throws more light than I do ) .

So its very easy to see that NFB is alive and operational in a triode.

[snip]


I am not a qualified university educated triodologist.

But my powers of observation reveal NFB in triodes to me.

But by exactly what process in purely technical terms would you use to
allege NFB does NOT exist in triodes?

Patrick, you're simply being stubborn at this point. We have pointed
out, over and over, that a plate resistance, which, so far, you CANNOT
and HAVE NOT proven does not exist, can account for all of the "feedback
effects," by which you mean damping, that you talk about.


The Ea / Ia at the quiecent state = 5,700 ohms for the 300B I mentioned.
But why does it measure 800 ohms when small variations in Ea are made?

Because the *model* of a triode includes a voltage offset in series with
a diode, caused by the grid. Given, say, -10 Vg, you will get no
positive current until you reach a certain plate voltage, enough to
overcome the voltage offset caused by the grid. Specifically, the grid
can repel the electrons until the plate voltage more or less equals the
grid voltage times mu. You get no negative current because a triode only
conducts one way, like a diode.

Similarly, if you have two resistors in series, with a battery between
them, you get no positive current when placing a voltage after the
second resistor until its voltage equals the battery placed between the
two resistors. A triode acts like a resistor with a voltage offset which
is controlled by the grid.



All you are doing like nearly everyone else is denying the summing NFB interactive
effects of anode voltage AND grid voltage upon Ia, and saying
the triode is merely a model of a battery or low Z voltage gene in series with a diode
or resistor which is equivalent to Ra.


Oh for god's sake WOULD YOU WAKE UP!!!


I am fully awake.

For the umpteenth time, the fact
that some theory fits the known facts regarding the dinosaur's demise
DOES NOT MAKE THAT THEORY TRUE! Patrick, no one is denying that you
could have a summing effect from plate and grid voltages, and I'm
getting tired of you telling me "you don't believe X" when I have told
you, over and over, that I have no evidence that X isn't true.


I see what consider to be factual, ie, true, and convey such ideas to you,
and nothing you have said so far leads me to believe that I should change a syllable
I have typed about NFB in triodes.

For the
umpteenth time, the fact that your feedback theory can explain things
does not, and will not ever, BY ITSELF prove that it is true! Why is
this so difficult for you to understand?


You don't accept evidence that where the sound of "quack, quack" is heard,
feathers appertaining to ducks are seen, feet of the bird have webbing,
bird can swim well, likes ponds, and also flies long distances.
I say a duck is what the bird is; it ain't a sea gull or a goose.....

What references or experiments
did you perform that PROVED that increasing the voltage across a triode
does not simply pull more electrons past all the obstacles in a triode,
in exactly the same way that increasing the voltage across a resistor
pulls more electrons past the thermally agitated atoms? When did you
PROVE that a simple resistance mechanism does NOT exist in a triode? Did
you never prove that? Then you cannot rule it out as a possible
explanation, period. Basic reasoning 101. Duh. And please, please don't
try to tell me that because your theory fits, therefore all other
theories are "proven" wrong (see dinosaur example above).


I hope I have explained plenty enough.
The rest is up to you to learn.
I am not the sole authority on NFB in vacuum tubes and to understand you will have to
look a lot harder elsewhere.

Just be prepared when you read what greater minds than I have written.

But you ain't proved there is not any NFB in a vacuum tube.

Don't you realise that you will find that proving me wrong is like pushing
rice grains uphill with your nose?
You would have to be far better equipped with knowledge.
And let me say I don't know of any text which conclusively proves NFB does not exist in triodes
so you are in an awful position intellectually.


A triode becomes like a diode when its grid is tied to the cathode or at a fixed voltage
in reference to the cathode; then there is no Vg-k variation, and no FB either,
because TWO voltage changes are required to make the loop for FB to occur.


What??? You know, up to now, I've thought your feedback model had real
merit, and I also thought you straightened out your thoughts on the
diode/triode issues, so let's get this straight. If I tie the grid to
the cathode, and increase the voltage across the tube, I soon get a
current of 100 mA and a dynamic resistance of, say, 600 ohms. But
there's no feedback here, according to you.


How can there be? its a diode, right, with Eg fixed at EK.
One arm of the NFB is present when the tube operates as a diode,
but its inactive in any voltage gain application.

The NFB in the AC operation is the summed effect of Eg and Ea.

If I tie the grid at -50 Vg,
and repeat until I reach 100 mA, I again find a dynamic resistance of
600 ohms. And again, according to you, there's no feedback??? But now,
if I put in an audio signal, but measure the dynamic resistance, I find
that it's 600 ohms, again, at around 100 mA, but NOW there's feedback???


The Ra appears to be 600 ohms because of the electrostatic effect the anode has on Ia.
One can't say there is a NFB shunt FB network present when one alters Ea to force the triode
into being a diode.
Resistors don't work on the same principle.

While the anode is free to move with a load, and the load voltage or anode voltage
is able to vary due to change to Eg, a NFB effect is evident.




Patrick, the whole point about the difference between triodes and
pentodes or transistors is that, given a *fixed* grid voltage, changing
the voltage across the tube causes a large change in current.


Not with a pentode.
If the pentode has a fixed Eg1 and fixed Eg2 with respect to Ek, pentodes
have a very high Ra...

Transistors also have a high Rc....

It has a
low output resistance. When the speaker tries to change its voltage due
to stored energy, the triode resists this, even if the grid voltage
happens to be constant at that time.


The load changes or distortion voltages arrising in loads, back emfs et all
are opposed by the triode because these signals all oppose themselves because of the
electostatic action of the anode upon the Ia.

Its the NFB arm working.
Screen that arm out with a screen as in apentode and the tube loses control of the load and becomes a
current source rather than voltage source. Ppl connect pentodes to loads, and
then use global NFB to do exactly what screen FB in UL amps does, or what the screen
does in triodes when strapped as such or what the anode is allowed to do in real triodes because there
is no screen.

Now, you can say that the change in
plate voltage changes the flow of electrons to the plate in the SAME WAY
as changing the grid voltage, which would be a feedback model. Or, you
can say that a triode fails to isolate a basic resistance mechanism
which exists in triodes and pentodes -- where increasing the plate or
screen voltage draws more current through the spaces between the grid
wires, just as increasing the voltage across a resistor draws more
current through the atoms -- from the plate voltage. In other words, the
screen *isolates* the inherent resistance from changes in plate voltage,
which would be a resistance model. So far, so good, but if you think
your feedback model requires feedback to "mystically" disappear every
time the grid voltage happens to be held steady, then you need to
abandon your feedback model, because that's clearly stupid. Mind you,
*I* won't abandon your feedback model, because I know that it does apply
to diodes, resistors, and triodes with constant grid voltages, and I can
accept that. But then, neither do I assume that such a weird model is
true merely because it, like other models, happens to fit the facts.


The NFB loop is simply the interaction of two fields acting on the Ia.

I make a distinction between diode action and triode NFB.
Both devices display low Ra ( compared to pentodes etc ) because the anode has
an effect on the space charge.

The one arm of the NFB loop exists in both triode and diode.
This alone does not mean that there is an interactive NFB loop present;
certainly not in a diode.





We already know all the triode models are true, but true because of the NFB.


A claim, backed up by nothing but faulty arguments (meaning you have no
proof).


But you have no proof I am wrong.



In a pentode there is also a battery or low Z voltage gene producing
µ x Eg and with an R in series which is equivalent to Ra.
In a pentode, µ = gm x Ra and without the NFB,
and for a 6AU6 µ approx = 0.0045A/V x 1,500,000 ohms = 6,750 at 7.6mA.

We can IMAGINE that the 6AU6 is a voltage gene with an output of
6,6750V for 1V input from a grid, and then
we have Ra as a series R = 1.5M and say we have a load of 20k then the current in the Ra + 20k
is 6,750V / ( 1.5M + 20k ) = 4.44mA and so the load voltage = 20 x 4.44 = 89V.

Thus the tube has a gain of 89.

If the load is altered and voltage readings taken then one can deduce Ra = 1.5M

If the anode voltage is altered by a low Z voltage source we find
Ra = 1.5M although Ea / Ia = 200V / 0.0076A = 26.3k, so how come
we measure the Ra at 1.5M?
Its because there is VIRTUALLY NO NFB, the opposite case to a triode.


Or because the pentode shields its inherent low resistance -- and if you
change the screen voltage, you will quickly see that such a low
resistance exists -- from changes in plate voltage.


Once you start altering the screen voltage as well as the grid voltage and allow Ea to move
on a load, or a CCS, then you have 3 things interacting to produce a given Ia or Ea
and things get much more complicated.
I have not time to talk about such tube operation and the math involved is also very complex.
if you really knew anything at all, you'd know all the math regarding triodes easily,
and find that math involving pentodes a real doddle as well and be able to
explain it all to us, rather than I be forced to explain a few things clumsily as I may manage to you...

I am not university trained, but I believe I have the concept of triodes right and that i know enough
about
pentodes & tetrodes to say what happens when one is connected in an amp with say 20% of CFB
connected locally around the OPT.
The math isn't as easy as it looks I may add, and someone told me that
if ever I wanted to understand electronics I'd have to be very good at maths.
I get by with my limited math ability, so my ears and meters and CRO tell me.

But where is your deep understanding?

All you have proven yourself to be is a knocker, a doubter, and based exactly upon what?


Reasoning 101, the
presence of one possible explanation DOES NOT PRECLUDE other possible
explanations. The existence of the phlogiston theory of combustion did
not prove that the Lavosier's oxygen theory of combustion was false.

If we connect the screen to anode, and triodise the 6AU6,
then the anode voltage is allowed to affect the Ia and
the apparent Ra drops because the µ drops from 6,750 to 36 due to NFB


OR because you are no longer shielding the low resistance from changes
in plate voltage. Tell me again, what does the NFB model achieve that
the low resistance model does not?


The low resistance of triode operation is because of the anode voltage effect on Ia.
One arm or the loop NFB is allowed to operate, so it operates, OK?



and the Ra = µ / gm = 36 / 0.0048 = 7,500ohms, so the NFB has a large
effect on reducing Ra.

What other mechanism do you suggest causes Ra to be so reduced?


The existence of a shield/screen that prevents changes in plate voltage
from accessing the low internal resistance, just as we have said (in so
many words) all along.

Then we should consider the case of a triode where there is NO ANODE CURRENT
CHANGE IN THE OPERATION.


Okay, I'll bite. Who knows? Maybe you'll actually prove that NFB is
indeed the preferred explanation.


I would prefer I share my observations and let you find your own truth.

The truth comes from proof, and if you don't accept my observations as proof
then you should never sleep again until you either proove to yourself what is true one way
or another, and I see you are sleeping and not prooving anything to anyone.





This is where there is a CCS load, and no anode current occurs.


No changes in plate current. Got it.

The summed effect of the grid and anode voltage upon the space charge
remains.


So? In other words, we can continue to view this situation using the NFB
model. Fine, that means that it has not so far been proven false. That
fact tells us NOTHING about the resistance model.


R = E / I. So where no current change occurs, R becomes infinite.
So some other way of thinking about the triode other than being a glorified resistance
must be considered.
Why does it operate so linearly when no Ia and only an Ea change occurs?
Most triodes are considered linear over small Ea changes with CCS loads.
The 300B is capable of 140V peak +/-V swing at about 1% THD only with CCS load,
how come the bloomin things does so much better than pentode, tetrode or any SS device
as a voltage amp?

Its not sufficient to say well, it just does it, because its like some kind of resistor.
That's not a deep enough answer.

So find the answer.



NO anode current change is possible because of the infinite resistance of the load.


True.

The NFB effect is maximal and voltage gain = triode µ.


Whatever (but Av = u, true).

Witha 6AU6 pentode with CCS, the µ = gain and would be 6,750 because
there is a very small VOLTAGE caused NFB effect.


Or, the resistance is not completely shielded from the plate voltage,
preventing u from being infinite. True.

How does one explain the tube working with CCS load without thinking of the
amounts of local NFB????


What's your point? In both cases, the grid-cathode voltage MUST change
if you are to change the plate-cathode voltage, although you need to
change it less with a pentode. So? With an unshielded resistance, the
grid-cathode voltage must change more to compensate for that unshielded
resistance. So? That's just another viewpoint of the same low plate
resistance of a triode.


One day you'll be able to think of 2 things at once while they are working together.
Not today it seems.






if there was no FB and the tube was just a purely passive device like a resistor,
the changes in Ea would give Ra = 5,700 ohms.
but we get 800 ohms.
How come?


See above.



You don't explain it.


I did explain it, you merely didn't understand it (which might not be
your fault). The voltage in series with a resistance model means that
you get no current at all until Vp is approximately mu x Vg, at which
point the 800 ohm resistance comes into play. That's the model, and it
correctly describes triode behavior.


Yes, in the
absence of tests which possibly can distinguish between anode resistance
and triode feedback, we really don't know which it is. But to claim that
feedback must exist *because* effects equivalent to either feedback or
low plate resistance exist is unscientific. You have a choice, and that
is why the rest of us simply state that, in the absence of any logical,
intellectual, or engineering advantage for feedback, we prefer low plate
resistance as a *model*. That's our choice. Maybe the other choice is
better. But you have not given any analysis to my knowledge which proves
that such a choice does not exist, or even that a feedback model is a
better choice for audio or electronics.


You call me stubborn, and refuse to proove I'm wrong, and you cannot deal with the idea
of the mutual effect of the two changing voltages of grid and anode which BOTH
have large effects on the Ia and so who is right?
If say I am wrong, then so is Prfessor Child, and all the guys with
better minds than yours or mine.

I call you stubborn because you claim that feedback exists, when an
alternative model explains everything (admittedly, as far I know) just
as well.



I won't call you stubborn.

The "alternative models" of a triode have been known by many for
70 years and are explained at my website and we agree
on the models of battery/voltage gene with series R to represent Ra.

But you still fail to see the NFB that exists.


Be fair and accurate here; I still fail to see a PROOF that NFB
correctly describes a triode, while resistance (plus a voltage) does not.

The models of generator + Ra resistance DO NOT explain or even include the NFB
effects, but are the models of the tube working AFTER TAKING INTO ACCOUNT WHATEVER NFB EXISTS.


I have no idea what your point is here.


I am beginning to think there is no point in trying to get you to see anything.




To say that it *might* be feedback would be okay, but until you
have proofs or experiments that rule out the resistor model, you cannot
say definitively that triodes have feedback.



I leave you to consider that minds better than yours have concluded
there is NFB within a triode.


That is merely an argument, an indication method, not a proof. By the
way, which better minds are you thinking of?

The plate may simply pull


electrons along in exactly the same manner as a battery pulls electrons
through an ordinary resistor.



No such pull along effect occurs in resistors.


Oh really? Pray tell how a resistor does work.


I am not going to tell you now.
I ain't got time. I am here for the tubes and I have to refuse explantations of the really basic stuff
when you show everyone you are so lazy for not reading up all about it elsewhere.

There IS much more on resistors for you to read first, so i won't have to
tell you, ever, or the group, some of whom have studied resistors
perhaps more than you have.



A resistor works in an entirely different manner to any tube.


Which would be ...


Then again, perhaps it would be *best*
described as feedback, and I can easily admit that.



The NFB is only evident when one considers the COMBINED NET EFFECT
OF TWO VOLTAGES within the tube, ie, grid and anode voltages.


Ridiculous, the low impedance of a triode is quite intact when the grid
voltage is fixed.


If not fixed, the Ra of the triode may be made as high as one wishes.

Furthermore, simply remove the grid from a triode
(there are several rectifiers where this was done), and I guarantee that
the dynamic resistance for a given plate voltage will be about the same
as in the triode version when the grid is tied to ground, and yet you're
claiming that the diode version does not have feedback, and therefore
should have a much higher resistance. Select equal current levels for
the diode version and the triode version using several fixed values for
the grid voltage, and you still get equal dynamic resistances. Put an
audio signal in, and measure the dynamic resistance at some moment in
time, you will still get the same values for a given current level. If a
triode has feedback, then a diode has feedback. That is NOT enough to
make me abandon the NFB model -- although it gave me pause for a while
-- why should you feel it's necessary to DENY that a diode has the same
feedback mechanism you claim exists for triodes?


Only one arm of the NFB loop is working when the input voltage is into the anode circuit
of a diode or into a triode anode when Eg = Ek or at a fixed voltage relative to Ek.
Where Ea is the output voltage as a result of input Eg, then a NFB loop
exists where such a two component loop cannot existin in the diode.




However, Henry has
some very convincing lines of reasoning that show no advantage or
greater accuracy or anything like that for feedback, I have not been
able to find lines of reasoning to contradict him, and again, as far as
I know, neither have you! I don't have to prove that triodes do not have
feedback to "prove you wrong," when all I am trying to claim is that you
are not necessarily right!



Try reading a few more books about triodes rather than seeking some
NFB de-bunking premise from Henry.
With all due respsect to Henry, he ain't the world's authority on vacuum tube theory.


He could be the devil himself, but that's irrelevant, along with his
knowledge, when it comes to the quality of his arguments on this matter.
You don't "disprove" a theory by saying the author is stupid or evil.
You ignore the characteristics of the author altogether, and focus on
the accuracy, or lack thereof, of the theory itself. Reasoning 101.


Its sometimes easy for me to discredit a theory without proof as i have at times.
I have not the time to be any better; I plead that I am human, and thus cannot
really change the minds fixed around me.
I will make to fine tubed amplifiers while the rest of everyone goes about their business
in perhaps greater ignorance than i have.

I seek to prod people to read and learn more rather than call me a liar.
Its really all i have time for, since explaining what I do know to the group to maintain
some semblance of a pool of tube craft knowledge is voluntary, and goes unpaid,
so this may be the ONLY place when your precious beliefs are challenged at all,
and those who don't expect to be challenged are living in an intellectual la-la
land of ignorant fairies.



Nor am I. So read up elsewhere. Until you have read a lot more, consider yourself ignorant,
because that would be a fact.


A general criticism without any support or examples. An old debating
trick. Useless ...


Let me see if I can make this clear. Let's assume, for a moment, that a
test will appear that truly can distinguish between low impedances
caused by feedback, and low impedances caused by a low impedance, a
simple resistance.



Resistances can be any value, and characterized by being a fixed value for a
large range of currents and frequencies.


The point was to assume, to hypothesize, that a test capable of
distinguishing between a NFB model and a resistance model exists. Given
that hypothesis ...


I do not know for certain what that test would tell
us about triodes. As far as I can tell, neither do you.



Well you are not able to hear or see what I have been saying.


That would indeed be one explanation. Another would be just the reverse,
that you insist on ignoring the fact that without a proof that one model
is correct, and the other model incorrect, you cannot justifiably claim
that the low output impedance of triodes is definitely due to a feedback
mechanism.

You don't want to accept you are mostv likely to be wrong, and ignorant.


That put-down doesn't necessarily follow from facts; it's just another
unsupported criticism, and therefore useless.

You have read almost nothing, have not benefitted from education,
and are at a similar position of where you might think you know your stomach's anatomy
by gazing at your navel.

**** you, Patrick. You know, every once in a while I think that Ian is
right; you're a bully.


I knew sooner or later I'd be told to get stuffed and be told that i was a bully.

Ian went around giving lots of advice on tube craft issues and he didn't even have a copy
of RDH4; its like being a Catholic priest without having a copy of the bible.
After some embarrassment and argy bargy and angst he has yet to forgive me for
he went and bought a copy of RDH4.
Then he enjoyed ridiculing much of its truth.

I think he succeeded in making a fool of himself, but I continued to challenge
his BS for years ever since.

he hasn't to my knowledge accepted NFB in triodes either, and I don't bother to argue with him.
I just say where I think he's wrong and move right along.
Its a public forum and whatever you believe in is challengeable.
That is the function of a discussion group.

People call me a lotta names and its all water off a ducks back.



Or at the very least, you act like one. Let me
get this straight. I'm just a stupid **** because I don't believe you
have proven your case? Let's see if I can put this in a manner you can
understand: **** YOU PATRICK!!! Take your pet, unsupported, unproven
theories, and shove them up your ass. If you can't discuss this matter
in an adult, intelligent, honest manner, than I have no further use for
you. Go use your bullying techniques on someone else. I'm not impressed.
Henry was right, I've wasted all the time on you I need to. Goodbye.


Fine, go away from the disission as ignorant as you came into it.

The people with real knowledge must be smiling at you.

I knew I'd get you sore when I said you hadn't read much.

Let's face it, you ain't read much at all abouty NFB in triodes,
and you know so little.

You ask so many questions and expect ME to prove it easy to you,
like spoon feeding you like a baby.

Sorry, but spoon feeding adults turns them into selfish brats,
so go learn about how and what happens in triodes and resistances
some where else if you can't find see any truth as i see it.

No hard feelings, just desire that you do more to educate yourself.

Patrick Turner.


Phil




THAT appears to
me to be the honest answer! Since resistor models are less complicated
than feedback models, I understandably believe that everyone should use
the simpler model until it is proven to be a less accurate description,
since humans make fewer errors when using simpler, but equally powerful,
models.



The simple models INCLUDES THE NFB AND USES VALUES FOR RA
which exist because of the NFB.

The models DON'T EXPLAIN OR INCLUDE THE NFB MODELS.

The models were invented TO BE A SIMPLIFIED TOOL for design purposes.


The MOMENT someone proves that feedback is the more accurate
model, I will state, publicly, that you were right, and that unless we
are working in some situation where there is no significant difference
between the two models, we should use feedback to describe triodes. But
not until then!

And honestly, Patrick, do you not agree that if triodes have feedback,
then so do resistors?



Resistors have no NFB in the same way pigs don't have wings and cannot fly.

Triodes do have NFB because there is an interactive voltage summing of two electrodes
which act upon the space charge.

I ask you to consider not making yourself look any more ignorant than you appear to be by likening

resistors to vacuum tubes in any way.


Batteries affect the electric field surrounding
the atoms in resistors, and increasing the voltage increases the field
strength, just as it does in triodes and diodes, and if it weren't for
that, the resistance would be much higher, perhaps infinite.



Huh?

This is a weird statement and I suggest you consult a professor of electronics
to guide you arrange words with more meaning.

maybe he'll give you a reading list if you decide to attend his classes at a university.

The exams they set at the end of such courses exist to guage whether or not
you understand what was in the books you may have read.




Mind you,
resistors might indeed have feedback, but until we find situations that
require us to view them in such a manner, why on Earth would we want to
replace the much simpler resistor model for resistors with a feedback
model? And the same question applies to triodes and diodes.



I suggest you don't know if there is or isn't NFB in resistances.
Find out for sure, will you, and let us know what you think and why.

You need to know, to understand.




Where is you alternative modelling?

We have stated it over and over and over again -- well, we've stated the
resistor part, perhaps the battery part was not stated as clearly as it
should have been -- I don't know how many times we are supposed to
repeat ourselves.



We agree on the models, but the models includes the NFB in operation.

The NFB loop elements are not included in the model because they were designed
to allow simple circuit analysis.

The triode model is low µ generator and low Ra series resistance, lots of local NFB.
The pentode model has high µ gene and high Ra series R, and very little NFB.

The model of a vacuum tube as a battery with series R is only correct for
DC operartion and is severly limited in its usefulness in applications
and the AC model with the battery being replaced with a generator
of low Z output resistance whose output = µ x Vg is the accurate model and useful
for both DC and AC operation.

Unless you understand the operation of the vacuum tube as AC generator with series R for Ra,
or else constant current generator = gm x Vg shunted by resistance = Ra then
your mind is severly limited for any exercize involving making up circuitry where
the current flows can be very basically examined.



I see there is NFB in a triode not because I am stubborn, but because
it hits me in the eye as being so very obvious, and its missing from
all other devices.

Yes, it appears to be feedback to you. It appears to be a resistance in
series with a voltage to everyone else.



There are many more ppl than myself who believe in the NFB withing vacuum tubes.

The model of resistance in series with battery or low Z voltage gene has been known for
70 years as a basic tool, and includes the effects of whatever NFB exists.

Because you cannot see the NFB, you say it cannot exist.

I say that not only is there NFB within vacuum tubes, but also that you are ignorant,
and in need of a serious increase in your education and you must forthwith
proceed without delay to a nice large pile of books wherin you may find answers
you are not getting from me.

Until you have read the books, and proved you understand what you have read, you
remain someone who is guessing his way through life, unguided by any real knowledge.

Patrick Turner.




Who is right? Until we have
better proofs than anyone has presented, on either side, that "the other
side's model" cannot fully account for a triode's behavior, we do not
know which one is truly correct, and therefore should use the simpler
model, and that is the resistance model.

Phil

Patrick Turner.




Phil




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Henry Pasternack Henry Pasternack is offline
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Posts: 14
Default Explanation still required for triode superiority

"Patrick Turner" wrote in message ...
Got me where?


You directly contradicted yourself. Three days ago, you argued that the
nonlinear plate resistance of a triode with Vgk FIXED is proof of NFB at work.
But yesterday, you stated the opposite, that NFB DOES NOT EXIST with
Vgk fixed. Which is it?

By your reasoning, if I have a common-cathode amplifier with an AC signal
on the grid, the output resistance of the tube will be low due to NFB. But
if I take away the signal, leaving only a fixed DC bias on the grid, the NFB
will disappear and the output resistance will rise dramatically. You and I
both know this doesn't happen.

By the way, did you know I studied EE in Frederick Terman's department?
He was professor emeritus, until he died, while I was at university. Some
of my professors were his former students, including a legend or two from
the "golden age" of tube radio, plus a good share of more modern legends.
I mention this because you raised the issue of academic credentials
yesterday.

I have to say, Patrick, you really don't know how to make a correct or
convincing engineering argument. And I do have the credentials to say
that. You are straining my patience.

-Henry


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Default Explanation still required for triode superiority

In article ,
"Henry Pasternack" wrote:

"Patrick Turner" wrote in message
...
Got me where?


You directly contradicted yourself. Three days ago, you argued that the
nonlinear plate resistance of a triode with Vgk FIXED is proof of NFB at
work.
But yesterday, you stated the opposite, that NFB DOES NOT EXIST with
Vgk fixed. Which is it?

By your reasoning, if I have a common-cathode amplifier with an AC signal
on the grid, the output resistance of the tube will be low due to NFB. But
if I take away the signal, leaving only a fixed DC bias on the grid, the NFB
will disappear and the output resistance will rise dramatically. You and I
both know this doesn't happen.

By the way, did you know I studied EE in Frederick Terman's department?
He was professor emeritus, until he died, while I was at university. Some
of my professors were his former students, including a legend or two from
the "golden age" of tube radio, plus a good share of more modern legends.


The crucial question is did any of the wisdom of these giants rub off on
you while you put in your time there.


Regards,

John Byrns
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Default Explanation still required for triode superiority

"John Byrns" wrote in message ...
The crucial question is did any of the wisdom of these giants rub off on
you while you put in your time there.


All I can say is I was fortunate to have the chance to learn from these people.

Here's a somewhat funny anecdote. When I graduated, I was applying for
a job at SRI International. Apparently they thought I was smart, but found
me to be quite obnoxious. Oswald G. "Mike" Villard (look him up), who
was retired by this time but working part-time at SRI, put in the good word
for me and I got the job. In the end, it worked out well.

I looked up Villard on Wikipedia last night and found out that he died in
2004. He was the real deal, a true pioneer and a heck of a nice guy. I
really had no clue at the time what a privilege it was to associate with
people like him.

-Henry


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Sander deWaal Sander deWaal is offline
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Default Explanation still required for triode superiority

John Byrns said:


In article ,
"Henry Pasternack" wrote:


By the way, did you know I studied EE in Frederick Terman's department?
He was professor emeritus, until he died, while I was at university. Some
of my professors were his former students, including a legend or two from
the "golden age" of tube radio, plus a good share of more modern legends.



The crucial question is did any of the wisdom of these giants rub off on
you while you put in your time there.



Dunno about that, but his analysis about the alleged feedback in
triodes (or absence thereof) made a lot of sense to me (at least the
parts that I could understand).
Henry seems to know his stuff pretty well.

I'm not that well versed in the theoretical department, so maybe it's
all flying over my head, but the conclusions that Henry posted and as
they were perceived by me, are at least uinderstandable and, what's
even more for a simple techie like me, cover the bases well enough to
not worry about it when designing my hobby amps with triodes ;-)

--
"Due knot trussed yore spell chequer two fined awl miss steaks."


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Andre Jute Andre Jute is offline
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Default Explanation still required for triode superiority


Henry Pasternack wrote:
"Patrick Turner" wrote in message ...
Got me where?


[snip]

By the way, did you know I studied EE in Frederick Terman's department?
He was professor emeritus, until he died, while I was at university. Some
of my professors were his former students, including a legend or two from
the "golden age" of tube radio, plus a good share of more modern legends.
I mention this because you raised the issue of academic credentials
yesterday.

I have to say, Patrick, you really don't know how to make a correct or
convincing engineering argument. And I do have the credentials to say
that. You are straining my patience.

-Henry


Congratulations, Patrick. You've just won the arguments hands down.
Henry Pasternack is known as Pompass Plodnick among other reasons
because he is a pompous asshole who every time he loses an argument
tries to steamroller with his diploma those he cannot beat by argument.
He is called Plodnick among other reasons because he is clearly a
plodder who learned a certain minimum of electronics off by rote, and
anything he did not learn off by rote is terra incognito to him. And,
as I explain to Phil in a concurrent post in this thread, Pasternack is
apt to lie on professional matters for the trivial satisfaction of
winning an argument; the "nick" part of his nickname is because he is
dumb Polack who always gets caught out in his lies. Google is full of
examples of Plodnick losing the argument and then bragging about his
education, being caught out in deliberate professional for personal
reasons, and suchlike immoralities.

Two other points are worth making. It is a shame that all that money
was spent on "educating" a fool like Pasternack when in effect it
merely assured that some bright, more worthwhile but poor kid didn't
get an education; such waste and misallocation of resources is almost
enough to turn one into a socialist. And it must be said that when a
man pushing 50, like Henry Pasternack, aka Pompass Plodnick, has to
justify himself by bragging about his education, you may be absolutely
certain in the assumption that his elite education bought him only the
most disappointing of careers, because the paymasters were not taken
in.

If employers are not taken in by the quarterwit Pasternack's diploma,
we needn't be either.

Andre Jute
Impedance is futile, you will be simulated into the triode of the Borg.
-- Robert Casey, funniest RAT of them all

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Default Explanation still required for triode superiority


John Byrns wrote:

"Henry Pasternack" wrote:


[snip]

By the way, did you know I studied EE in Frederick Terman's department?
He was professor emeritus, until he died, while I was at university. Some
of my professors were his former students, including a legend or two from
the "golden age" of tube radio, plus a good share of more modern legends.


The crucial question is did any of the wisdom of these giants rub off on
you while you put in your time there.


Regards,

John Byrns


Pasternack's transparent namedropping is intended to imply that the
wisdom of Terman and his best students rubbed off on him. It's bull****
of course. Next Plodnick will claim that Worthless Wiecky is the equal
of Peter Drucker (1) because Worthless was the janitor at the Wharton
School of Business! (2)

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

(1) Peter Drucker was the greatest theorist of applied economics
(business management) who ever lived.

(2) Yes, my darlings, I know where the Philadelphia is, and I know
where New York is, but if we're dropping names, what's few miles?
Reminds me of the time when the chairman of my ad agency had this
brilliant idea (he was always having brilliant ideas unless we were
extra-vigilant): we would hire Drucker as a consultant. So a deputation
of the directors went immediately to Drucker's office to make him an
offer he couldn't refuse. My chairman was a huge fellow in his early
thirties with short, very blond hair. The rest of us were muscular
young men (high-profile sporting achievements were essential to rising
in our organization -- that's how we met most of our clients) of
definitely Aryan stock. We all wore double-welted leather-soled shoes
from Lobb in London and you can bet your ass a bunch of young guys who
earned seven-figure sums walked down this long passage before Drucker's
office with heel-clattering confidence; most of us had been in the
military somewhere (this was still in the age of conscription, where to
avoid forcible induction you did ROTC) so we clattered in step, like a
firing squad marching. Drucker was a Hungarian, a refugee from the
Nazis... One of the PA flung the door open dramatically and we bent our
heads to get through the door, then stormed up to a halt before the
desk behind which this little guy cowered. My chairman said, "We have
come for you!" Drucker stuttered, "I'm an American citizen now!"
Needless to say, we didn't succeed in hiring him.

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Phil wrote:
Patrick Turner wrote:


Try reading a few more books about triodes rather than seeking some
NFB de-bunking premise from Henry.
With all due respsect to Henry, he ain't the world's authority on vacuum tube theory.


He could be the devil himself, but that's irrelevant, along with his
knowledge, when it comes to the quality of his arguments on this matter.
You don't "disprove" a theory by saying the author is stupid or evil.
You ignore the characteristics of the author altogether, and focus on
the accuracy, or lack thereof, of the theory itself. Reasoning 101.


Unless of course the party in question has a track record of
deliberately lying. In the case of Henry Pasternack, often referred to
RAT as Pompass Plodnick, Google archives show a long history of
Pasternack lying on professional and other matters for the sake of
"winning" some argument, and of Pasternack committing other
unscientific and immoral acts, for which his only excuse is, once the
further lies are stripped away, in Pasternack's own words, "my zeal to
flame Andre".

In this particular case Pasternack came here hoping to have a big fight
with me but I merely patronized him a little and sent him on his way
with a flea in his ear; he was stuck with Patrick. Because Pasternack
came for me first, and because of his history of lying on professional
matters for personal gratification, and because Pasternack's first post
on the subject (to Chris Hornbeck) was ambiguous, we don't actually
know whether he really believes what he says now, or whether his hatred
of me has once more painted him into another corner which he will now
try to justify with a berm of math.

Those new to RAT who wish to see earlier examples of Pasternack lying
on professional matters for personal gratification should look up the
case where Pasternack told a newbie not to listen to me when I advised
a primary impedance on his output transformer 2*Rp or higher;
Pasternack told him instead to choose an output impedance equal to the
plate resistance. Read that again. Pasternack surely knew that the
primary impedance should be twice or more the plate resistance but he
lied about it to a newbie "in my zeal to flame Andre". There are
hundreds of further posts in Pasternack which tried to justify his Zo =
Rp stance but eventually John Byrns nailed Pasternack's hide to wall.
Other examples are plentiful, and I have already in this thread given
references to a URL that proves Pasternack's contempt for the
scientific method.

Furthermore, Pasternack in the throes of his hatred will commit totally
immoral acts. He ran with Michael LaFever's Magnequest Scum, who
flooded the single driver conference with graphic homosexual
pornography sent in my name in an effort to drive me out; they were not
there before I came, they were not there after I left. Some of that was
traced to Pasternack's server.

Even worse is the case of the two little girls of an Italian engineer
who built one of my designs. He accused Pasternack of sending graphic
homosexual filth to his computer, where his two little girls saw it. He
didn't even know who Pasternack was when he traced the filth to
Pasternack. Pasternack's Magnequest Scum associate Bob Chernofsky said
on the Joenet (there's an archieve at Harvard if you want to look it
up; search for Sound List) that Pasternack did it because he was bored
with not being able to get at me directly.

Do you really want to hold this scumbag Pasternack up to us as an
impartial fount of engineering wisdom?

Get real, Phil. We know better, and it is up to newbies like you to
inform themselves before they goof up dumb opinions.

Andre Jute
Stop bleating. Please, please, please give me the Silence of the Lambs.

PS Do I need to explain that we shall know by your response to my sharp
remarks how steady your judgement is?

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Default Explanation still required for triode superiority

In article , Sander deWaal
wrote:

John Byrns said:


In article ,
"Henry Pasternack" wrote:


By the way, did you know I studied EE in Frederick Terman's department?
He was professor emeritus, until he died, while I was at university. Some
of my professors were his former students, including a legend or two from
the "golden age" of tube radio, plus a good share of more modern legends.



The crucial question is did any of the wisdom of these giants rub off on
you while you put in your time there.



Dunno about that, but his analysis about the alleged feedback in
triodes (or absence thereof) made a lot of sense to me (at least the
parts that I could understand).
Henry seems to know his stuff pretty well.


This discussion isn't a matter of knowing much of anything, if I read
Henry correctly he is not saying that the operation of the triode doesn't
involve NFB, or that it does for that matter, all Henry is saying is that
there are several alternate ways to describe the operation of the triode
when it is viewed as a black box. Henry's logic can equally well be
applied to other devices, like say the famous Williamson amplifier, to
describe their operation without reference to NFB. The fact that a device
can be described by a Thevenin or Norton equivalent circuit says nothing
about whether or not the device makes use of NFB as part of its internal
operation. Given that both viewpoints are valid in a mathematical sense,
this whole discussion is just so much pointless gum flapping.

I should note that I only rejoined this group a week ago, and while there
appear to be numerous threads that may be discussing this subject, I have
only looked at two, first the "Diode" thread, and today this thread.
Since I have been only selectively reading the posts here, I may be
missing some crucial history which could render some of my comments
invalid, YMMV.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/
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Default Explanation still required for triode superiority

"John Byrns" wrote in message ...
This discussion isn't a matter of knowing much of anything, if I read
Henry correctly he is not saying that the operation of the triode doesn't
involve NFB, or that it does for that matter, all Henry is saying is that
there are several alternate ways to describe the operation of the triode
when it is viewed as a black box.


That is one of my conclusions, but not necessarily the most important
one. The main purpose of my postings has been to dissect the triode
NFB claims, and to debunk them -- carefully and critically. Doing so
requires both knowledge and analysis skill.

You always try to diminish what I have to say. You're just far more
restrained than Andre.

-Henry


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