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  #161   Report Post  
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Andre Jute Andre Jute is offline
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Default Explanation still required for triode superiority


Sander deWaal wrote:
"Andre Jute" said:


These, incidentally, are the same test results I interpret as meaning
that there is no such thing as an SE sound, that what we hear which so
appeals is a Class A ZNFB or very low NFB sonic signature. People just
confuse Class A with SE because only a tiny, tiny minority even of the
ultrafidelista have ever heard pure Class A PP amp.



Well, I have, since that's about the only topology I use when building
tube amps.


Join the elite.

I compared triode strapped JJ KT88s against NOS Philips XF4 EL34s,
also triode strapped in the same circuit, with somewhat reduced supply
voltage to not overstress the EL34s.

For me, the KT88s won hands down, even with the lower anode voltage.


Your membership has just been revoked! Next you'll be wanting 6550s.

I posted the circuit diagram some days ago in the "Step 2 for Fisher
Iron" thread.
You can still find it here, if you're interested:
http://img508.imageshack.us/img508/1751/wkschemod0.jpg


Vrij naar Murphy: de hoeveelheid problemen op een versterker neemt toe
met het
kwadraat van het aantal onderdelen.

Unless one wants a SE amp, it doesn't get any simpler than that, I'm
afraid.


There's a certain elegance to simplicity: you see it and you know the
thing will work well before you even get into the subtler details.

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


Andre Jute
Nah, Murphy is my insurance agent. He wouldn't dare. It would cost him
too much.

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Chris Hornbeck Chris Hornbeck is offline
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Default Henry Pasternack's Norton triode model???

On Thu, 12 Oct 2006 03:01:33 +0200, "Ruud Broens"
wrote:

...so Ia=k*Vak^3/2, with k some geometrically determined
: constant.
:

better formulated as: so, by induction, we know Ia is proportional to Vak^3/2,
the multiplier k being dependent on geometry and cathode emission


This is actually the approximation for a diode, but the
form for a triode is similar.

Please note that these are approximations. Put another way,
k is not constant, and not linear. It's the k part
that's interesting.

Thanks, as always,

Chris Hornbeck
  #163   Report Post  
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Andre Jute Andre Jute is offline
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Default Henry Pasternack's Norton triode model???


John Byrns wrote:
In article ,
"Henry Pasternack" wrote:

I believe Byrns' point is that a three-halves power transconductance
whose input is the sum of Vg and Vp / mu is one such model.

There's no general way to represent the large-signal model in terms
of an independent transconductance and admittance. But we don't
need to solve the general case to disprove the feedback proposition.

Because there are no cross-terms in the triode equation,


Henry blows it here because the triode equation I posted,
Ipk = k * (Vgk + Vpk/u) ^ 1.5 actually does include "cross-terms",
although Henry would like us to believe it doesn't.

if you set
the condition that Ip is constant, the three-halves power exponent
goes away and Vp becomes a linear function of Vg. Then gm has
no dependence on Vp and rp has no dependence on Vg. This is
why all the plate curves have the same shape.


This of course is not true, all the plate curves in a real triode, as
well as in my model, do not have the same shape.

You can derive the
Norton model assuming a nonlinear transconductance that is a
one-half power function of Vp and a nonlinear admittance that is a
negative one-half power function of Vg. The product of the two is a
constant, equal to mu. The model meets the requirements that it
has no feedback and also that it expresses the Child-Langmuir
equation.


To correct a typo "Henry Pasternack" then wrote:

You can derive the Norton model assuming a nonlinear transconductance
that is a one-half power function of Vp and a nonlinear admittance that is
a negative one-half power function of Vg.


Before Byrns and Jute get hysterical, let me say I inadvertently reversed Vp
and Vg in that sentence.


OK, after correcting that typo has anyone been able to make sense of
Henry's Norton model? As near as I can tell, for the plate circuit to
express the Child-Langmuir equation, it is necessary for Henry's
nonlinear admittance to be a positive one-half power function of Vp, not
a negative one-half power function of Vp as Henry said, is this another
typo?


Regards,

John Byrns


This entire debate is from Pasternack's viewpoint a political matter.
When he first blew in here he was ambivalent about the whole thing,
placing a limp bet of a dollar each way. Then he discovered that I was
very strongly on one side, so he had to take the other side. Then he
gets it wrong, as above, not just in the details but fundamentally. You
and Patrick and I have a very strong case and those in opposition have
a case that seems weaker by the minute and is now clearly lost. So
Pasternack hurled some low-voltage thunderbolts, his battery ran flat,
and he ground to a halt. Usual story with Plodnick; he's a slow learner
who will embarrass himself again and again and again. I feel sorry for
guys like Chris Hornbeck and Ian Iveson who look up to Plod as some
kind of a champion; they are only the latest in a long line to be
disappointed in Pasternack.

About Pasternack's chaotic case of "a nonlinear transconductance that
is a one-half power function of Vp and a nonlinear admittance that is a
negative one-half power function of Vg" -- gee, when I say I we need to
go back to basics, I don't mean all the way back to the BIg Bang, even
if that slow learner Plodnick can ever get it right first time.

So, I am not even trying to make sense of Plodnick's Norton mess; he
didn't intend us to; he threw it in as a smokescreen and a disruption,
a spoiler.

But it might be entertaining on a slow, rainy winter's day to stand
Plodnick up on a rickety soapbox and make him try to prove it...

Andre Jute
Habit is the nursery of errors. -- Victor Hugo

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



Sander deWaal wrote:

"Andre Jute" said:

These, incidentally, are the same test results I interpret as meaning
that there is no such thing as an SE sound, that what we hear which so
appeals is a Class A ZNFB or very low NFB sonic signature. People just
confuse Class A with SE because only a tiny, tiny minority even of the
ultrafidelista have ever heard pure Class A PP amp.


Well, I have, since that's about the only topology I use when building
tube amps.

I compared triode strapped JJ KT88s against NOS Philips XF4 EL34s,
also triode strapped in the same circuit, with somewhat reduced supply
voltage to not overstress the EL34s.

For me, the KT88s won hands down, even with the lower anode voltage.

I posted the circuit diagram some days ago in the "Step 2 for Fisher
Iron" thread.
You can still find it here, if you're interested:
http://img508.imageshack.us/img508/1751/wkschemod0.jpg

Unless one wants a SE amp, it doesn't get any simpler than that, I'm
afraid.


It could be simpler.
The 12BH7 driving triodes have about 3dB of applied series voltage NFB
from KT88 triode anodes to BH7 cathodes via the 300k/1k5 networks.
This means the anode resistance of the KT88 is effectively reduced from
about 1k to about 650 ohms, so thus compensating for the winding resistance
of the OPT
as seen at the secondary. But is this NFB really worth applying/
Its such a small amount, and around low µ triode outputs it doesn't do very
much.


But I agree that PP 6550 and KT88 and KT90 are splendiferous when triode
connected
and its difficult to have them sound bad.
And they are fine in SET based designs.

Patrick Turner.





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


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



Andre Jute wrote:

Sander deWaal wrote:
"Andre Jute" said:


These, incidentally, are the same test results I interpret as meaning
that there is no such thing as an SE sound, that what we hear which so
appeals is a Class A ZNFB or very low NFB sonic signature. People just
confuse Class A with SE because only a tiny, tiny minority even of the
ultrafidelista have ever heard pure Class A PP amp.



Well, I have, since that's about the only topology I use when building
tube amps.


Join the elite.

I compared triode strapped JJ KT88s against NOS Philips XF4 EL34s,
also triode strapped in the same circuit, with somewhat reduced supply
voltage to not overstress the EL34s.

For me, the KT88s won hands down, even with the lower anode voltage.


Your membership has just been revoked! Next you'll be wanting 6550s.


Andre, say it slowly, s-i-x-t-y f-i-v-e f-i-f-t-y. There now, surely your
brain didn't explode,
or internally melt down like an over driven EL34, now did it? ;-)

At some point in the future I will coax you into saying KT90 EH without
wincing in pain.......

Patrick Turner.






I posted the circuit diagram some days ago in the "Step 2 for Fisher
Iron" thread.
You can still find it here, if you're interested:
http://img508.imageshack.us/img508/1751/wkschemod0.jpg


Vrij naar Murphy: de hoeveelheid problemen op een versterker neemt toe
met het
kwadraat van het aantal onderdelen.

Unless one wants a SE amp, it doesn't get any simpler than that, I'm
afraid.


There's a certain elegance to simplicity: you see it and you know the
thing will work well before you even get into the subtler details.

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


Andre Jute
Nah, Murphy is my insurance agent. He wouldn't dare. It would cost him
too much.




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Peter Wieck Peter Wieck is offline
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Default Henry Pasternack's Norton triode model???


Andrew Jute McCoy in its usual diversionary way bleated:

But it might be entertaining on a slow, rainy winter's day to stand
Plodnick up on a rickety soapbox and make him try to prove it...


How about you proving your imaginary visit to Peter Drucker first... or
did you mean a strange Hungarian of the same name?

Peter Wieck
Wyncote, PA

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Ruud Broens Ruud Broens is offline
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Default Henry Pasternack's Norton triode model???


"Chris Hornbeck" wrote in message
...
: On Thu, 12 Oct 2006 03:01:33 +0200, "Ruud Broens"
: wrote:
:
: ...so Ia=k*Vak^3/2, with k some geometrically determined
: : constant.
: :
:
: better formulated as: so, by induction, we know Ia is proportional to Vak^3/2,
: the multiplier k being dependent on geometry and cathode emission
:
: This is actually the approximation for a diode, but the
: form for a triode is similar.

actually, it's more general than that, it is applicable to all tubes
under space charge conditions, subject to modification when there are
more influences (such as grids). in a penthode, for instance, the diode
curve comes back for both G1 and G2 voltage vs Ia.

:
: Please note that these are approximations. Put another way,
: k is not constant, and not linear. It's the k part
: that's interesting.
:
well, i said, "almost too simple ..."
to a physicist, this type of first approximation reasoning looks
very familiar, i can assure ya ;-)
a perfect mathematical model would be the result of a summation
over a large number of near-identical parallel 'mini tubes'.
in a triode, eg, you'd have to account for variation in cathode
temperature and emission over it's surface, the non-perfect
uniform grid wire spacing and distance to cathode, non symmetries
because of the needed physical support structure, etc., etc.

where measured curves will deviate most from the first order
model, is at really low currents, even a sharp cutoff tube has
some variance in mu there
but take the recently mentioned 18046 in triode, that has a
virtually unchanged mu over a 200V plate voltage range
when run above 10 mA
(and the usual suspects, 300B, 2A3, etc. do likewise)

Rudy

: Thanks, as always,
:
: Chris Hornbeck


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Andre Jute Andre Jute is offline
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Default Was CFB and UL really specifically intended to combat NFB recombinants? was Explanation still required for triode superiority

One of the really irritating things on the usenet is when you write a
long, detailed post full of facts and opinions -- and find everyone so
much in agreement with you that no one replies. It feels like you're
out in a vacuum somewhere, whereas in fact everyone is just sitting
there nodding wisely, saying, "I knowed that," and not posting a
response because they have nothing to disagree with or add. (For the
non-Anglophones, "I knowed that" is not bad English but a schoolboy
joke.) Patrick must feel like that after his two recent long, detailed
posts full of relevant numbers. I especially enjoyed the historical
references, and sure, I agree, the EF86 is a wonderful little pentode.

But the only question I want to raise on two whole long posts from
Patrick is one so tangential that it needs a subthread of its own.

Yo, Patrick: you say that the inventors of CFB and UL *intended* by
their inventions to get all the advantages of the triode, including
specifically the advantageous harmonic distribution, together with most
of the power of the pentode. Can you cite any documentary proof of a
deliberate intention with reference to harmonic proportions at this
early date, say the late forties or early fifties? Or is your remark
the result of hindsight brought on by your own, much more recent
observations, and simply reflected back upon those guys -- IOW am I
just reading too much into your statement?

TIA.

Andre Jute
Twenty-twenty hindsight

Patrick Turner wrote:
Andre Jute wrote:

John Byrns wrote:

In article .com,
"Andre Jute" wrote:

I'm reading this part of the thread with great pleasure; it reminds me
of the glory days of RAT when high theory was everyday meat on the
table.

There's some confusion here about which tubes we're talking about.
Perhaps I am to blame for it, in phrasing the thread headline too
bluntly as "triode superiority". But the results of tests and my actual
opinion, which comes as no surprise to you, is not the unqualified
"triodes are superior" but that "ZNFB or low NFB Class A1 triodes and
trioded pentodes are superior on the ear of qualified listeners to any
other form of reproduced music". My best amp ever, in the ears of my
test groups of professional performers, is PP EL34 Class A running ZNFB
or less than 6dB of NFB; I usually test it against expensive 300B gear
either of my own decising or commercially available and *behind the
curtain* it usually wins.

Next, the problem with pentode sound is not so much the pentode itself
but the amount of NFB required to get it to deliver its power with any
pretense to quality, the NFB creating recombinant harmonic artifacts
which are very disturbing to qualified listeners. Thus, if we use any
NFB at all in the levelling process, as in the CFB example, the
question is opened up of the recombinant harmonic effects of NFB *which
we are then adding to only one of the contestants*, the pentode, to
disadvantage the pentode yet again.

Hi Andre,

Please cut me a little slack if I have missed something, as I wasn't in
on this thread from the beginning.


The necessary information is spread over many threads and my netsite.

I don't understand your apparent
thesis that the triode is superior, if indeed your "PP EL34 Class A
running ZNFB" is your best amp ever, as judged by your "test groups of
professional performers"?


The headline is a provocative outgrowth of a bad-tempered set of
threads on whether a triode has native or built-in negative feedback. I
have always said that best amp I ever built was the trioded EL34 PP. In
fact I spelt it out earlier in this thread as well, but nobody took the
slightest notice.

Are the EL34s in this amp triode connected
with the screen grids strapped to the plates?


Yes.

If this is the case, the
implication is that an EL34 with the screen tied to the plate makes a
better triode than the 300B used in several of your other amp designs?


Yes. The comparison is ZNFB or very low NFB triode strapped EL34 PP
against SE ZNFB 300B. In level matched tests with a third, usually
solid state placebo amp also behind the curtain, a sophisticated
listening panel will choose the PP EL34 pseudo-triode amp every time.
(The SS amp commonly gets no votes.)

There are complications, in that when you double up the tubes on each,
to compare PSE and PPP, all other factors equal, except that now you
can use better speakers, specifically ESL63, the results get a bit
closer simply because the speakers offer more resolution to a test
panel accustomed to listening to details, and that big broadcasting DHT
like 845 and SV572-xx whip little EL34, but for practical,
level-matched tests at the entry level -- not meaning money, for all
these amps are expensive, but the entry level of very high resolution
-- sure as hell triode strapped PP ZNFB EL34 hold the upper hand. You
have to be in PP 300B at umpteen-eleven times the price, with a lot of
high-ticket high-carriage iron on board, before the natural triodes
make as good a showing as the humble, inexpensive, ultra-versatile
EL34; by then it is clearly no longer a fair test (but then, in terms
of high street hi-fi prices even the base EL34/300B test has only a
tenuous connection to what most people would regard as reality).


I have heard music via a pair of made in HK 18watt Vincent PP amps using two
300B
which to me did all the business really well.

it wasn't an expensive amp in1995, when I used to attend the NSW Audiophile
Society's meetings
to see what other folks got up to.

For PP triodes and 18 watts you need about 400V and 150mA,
and an OPT with about 8k : 8 ohms, and your'e away.
The same PS could be used for a pair of EL34, and get less power, or a pair of
6550 in triode
for maybe slightly more power. But the iron need only be about the same and not
cost a lot'
the cost is mainly in the higher costs of the 300B and perhaps in its needed
pair
of 5V filament supplies.
I personally don't see any point to using EL34 in triode when for such a small
extra outlay
6550 or KT88 in triode could be used and which would have lower Ra-a
and more power which is very much worth that slight extra outlay.





I give you the additional information because we need to be clear that
what I have proved isn't that PP amps are better than SE, merely that
the EL34 is a stonking good tube, especially at the price.


Also don't forget the EL34 replacement called the 6CA7, a beam tetrode, also
an underated tube.
I had to do a minor repair on a 'THD" branded SE guitar amp last week
which had a Russian 6L6GC running with 45 watts of anode dissipation with the
anode only
a tiny bit red in one place. It was fine at 35 watts.
EL34 will glow red with less Pda than this 6L6GC.
So I it seems the humble 6L6GC now made with its actual higher pda capability
well above the
original 22 watt rating could produce good triode power in a PP circuit.



The test
only incidentally pitches a PP against an SE amp; I had long before
this discovered that SE or PP matters not when both are made with
triodes running in Class A and you have a very light or absent hand on
the NFB; what I set out to prove in these later tests with the PP
trioded EL34 was something about Class A sound, and something about the
composition of distortion, and something about the lowest imperceptible
level of loop or anyway additional NFB.


I tried PP EL34 in triode in a pair of Quad II amps for 13 watts with 6db of
global NFB
and the owner said it lacked the sparkling
dynamics of a 10 watt amp using 6GW8 in class AB1 and about 17dB of GNFB.
Only when i went to KT88 in triode with 12 dB of GNFB did the owner say that
the
Quads then sounded as good as the UL amp and that the bonus was a slighty
higher ceiling
because the KT88 in triode with Ea at 400V and fixed bias the amp gave 20 watts
AB1.
There is lots about modding Quad II at
http://www.turneraudio.com.au/quad2powerampmods.html

I conclude from my observations and from what customers tell me that 12dB of
NFB is fine in a
triode PP amp. Nobody I know can tell the difference between
a normal triode amp with 12db of GNFB and the same amp with its screens taken
to UL
taps and with the FB left the same.


You also seem to be saying that the negative feedback that is inherent


in the operation of a triode is not responsible for its superior sound,


On the contrary, it seems to me very likely that the negative feedback
inside a triode is responsible for the quality of its sound. To me it
is a very persuasive argument that to bring a pentode back even partway
towards the silence of a triode you have to use the NFB that was taken
away to make it a pentode!


Well, yes, but impossible....



However, it is clear to me that external forms of NFB, as in loop
feedback, UL, CFB, etc, act differently to the native or internal NFB
of a triode. This is easily seen in comparative harmonic output
analysis of an EL34 amp with a pentode/UL/triode switch and a pot or
switch to alter the amount of loop NFB, as in my T113 "Triple Threat"
PP EL34.


Well indeed there IS a difference in FB transfer between external and triode
internal transfer.

Local or global NFB loops are normally employed in linear mechanisms; ie the
CFB of an OPT with CFB is where
the cathode voltage is magnetically locked to the energy elsewhere generated.
The fed back voltage is exactly the same in spectral content at the cathode as
at the anode'
only the phase is opposite.
The local CFB with screen fully bypassed to cathode acts to reduce all the
spectra of the
pentode without NFB, and most pentodes suffer double digit THD at clipping when
tested
to gain the published data for SE use; 13% THD is about what is quoted, and a
horrible mix compared to
the 5% of the trioded case, with most only 2H.
Note that these figures are for the rated load use stated for the tube;
Loading means a heck of a lot with output tube distortions.
Unloaded, the pentode is abysmally horrible.
But when CFB or external GNFB is added, the higher the load, the higher the
gain
so for a given value of ß, the greater tha amount of NFB applied, so although
the
THD rises as load increases with no NFB, it is limited in rise when a given
amount of NFB is applied.
The triode THD reduces to almost nothing when load value is very high,
indicating
its inmternal FB is maximally effective, similar to the case od the unloaded
pentode with a given amount
of CFB as i calculated in a previous case for the EL34.

When loaded though, the gain of the triode goes lower, and the internally
applied amount of NFB becomes lower
but still present, and the transfer of the NFB becomes maximally affected by
the nonlinear 3/2
voltage effect on Ia.
A similar thing occurs in UL, but intermediate between triode and pentode,
and somewhat unique, ie, different to either triode or pentode.

A UL amp with 43% taps and EL34 may make a maximum of say 32 watts,
and in triode its 14 watts, but the UL amp will have no more THD than the
triode amp at 5 watts,
and be spectrally as clean.
Trouble is the Rout. The UL amp has Rout about = RL, and GNFB must be used to
further reduce Rout.

In the past many makers competed with each other to get the highest possible
amount of GNFB applied around their UL
amps to be able to say they had 0.03% THD at 45 watts.
30db of applied GNFB was not uncommon in top brands using
well made OPT.
Meanwhile all the makers with lesser quality OPTs had to settle for no more
than the standard 20dB
of GNFB and 0.3% THD at clipping for class AB1.
Now 17db is a lot of GNFB around any tube amp.
In actual fact, few could really tell the difference between samples of all the
above
amp recipes at average normal listening levels of 86db, or 1/2 a watt average
to each of two speakers.
Nobody is going to win any prizes for applying more than just enough GNFB
around any tube amp these days.
Sanity has prevailed; we have done away with the uneccessary.

A UL amp with 50% taps and in class A PP with 6550 typically makes 1% THD of
mainly only 3H
at about 30 watts and without GNFB.
At 3 watts, output voltage is 1/3 of clipping, and THD is about 0.2%, and at 1
watt
its THD is about 0.11%, and THD is already so low that it isn't of any concern
and would
not be discernible by 99% of the population.
However, the Rout would seriously colour the sound, depending on the vaguaries
of speaker Z
so if 15dB of NFb were applied, the typical Rout without NFB of about 5 ohms
if the secondary winding was a match for 5 ohms is reduced to about 0.7 ohms.
All is well if the OPT has wide BW to start with and the driver amp is suitably
set up.
people knock UL amps with 6550, but it has been my experience to seriously dent
all the
egos of other makers of amps with triodes and low GNFB with samples of mine in
demonstrations with the
audiophile club, and while using 1/2 the output tube count.

I have nothing against trying to use zero GNFB and rely on just the natural low
Ra of the triode.
But I would say that then one is compelled to use wide BW OPTs, lest the OPT
unecessarily act as a filter,
so don't try an old Leak Point 1 TL12 without its GNB in triode; the OPT has
50mH of leakage inductance!
And one wants low winding loss OPTs, and with a nice high voltage ratio
to give the output tubes a higher than normal AB1 loading.
So when thinking of EL34 in triode I'd be thinking of 10k : 6 ohms OPT ratios,
using Ea = 425V, Ia = at least 50mA.
The Ra-a of the triode = 2.5k, and this is transformed to 1.5 ohms by the OPT Z
ratio
of 1,666:1.
Then one adds the effective winding resistance of say 0.4 ohms at the sec and
you still get
Rout at about 1.9 ohms.
This is one reason why not to use EL34 in triode when 6550, KT88, or KT90
will all give you 1.5 ohms under the same conditions.
But the larger tubes allow a higher safe Ea at the same Ia, and so RLa-a can be
higher,
say 12k : 6 ohms, or 2,000 : 1 so the Ra-a of 1,800 ohms is reduced to only 0.9
ohms,
and plus Rw, Rout = 1.3 ohms. 300B will do slightly better since the Ra is
slightly lower than
any of the larger octal power tubes in triode.
The benefit of having each output tube seeing a class A load of 6k each is that

the THD also is quite low, and negligible at ordinary listening levels.



do you have any clues yet as to exactly what it is that is responsible
for the superior sound of the triode and the triode connected pentode?


Sure. The difference in sound between a triode (natural or screentied)
and a pentode is caused by the different makeup of the harmonics.


Especially the IMD caused by the varying gain with load changes.
In the pentode, these are high, in the triode low, and its a function of the
Ra....


Regardless of the absolute level of distortion, the triode, however
made, has a lower proportion of odd and higher harmonics than the
pentode. It is known that very low percentages of odd and higher
harmonics can cause uneasiness in listeners.


This very true, and when i built a pair of SET 4 watt amps using 2A3
they sounded cleaner than the same power from an EL84 in pentode with global
NFB.
However, I do have a pair of SE amps with EL84 with about 10% CFB and slight
NFB
and these are remarkably triode like, and very listenable.

I think the 2A3 gives the best 4 watts possible out of all devices in the
universe.

It is strong supporting
information that the difference between a good 300B amp and a bad one
can be read in the proportion of 3rd harmonic left on the bad amp (as
you yourself showed in a table when you compared my HVHCHL "Hedonist"
to the distrastrous BobC/LaFevre/Magnequest "Bubbaland" amp roundabout
1998 -- that was a big clue on the way to my present understanding --
thanks!).

The easiest way to prove the importance of the proportions inside the
THD to yourself is to put a pentode/UL/triode switch and an NFB pot on
a pentode amp and to study the makeup of the distortion in each mode at
various levels of NFB including zero NFB. Of course, it took me a bit
longer than a single sentence, because I had to eliminate all the
common factors between the various topologies (I wasted years on AC
balance in PP amps) before I isolated the odd factor and could examine
it closely. There is no other parameter where the change is so striking
and so inexplicable. Even at zero NFB, the third and higher harmonics
fall through the floor when you turn the triode switch on a pentode
amp.


Well, switching that switch from pentode to triode is connecting the triode FB.

Ra falls heaps, the iron distortions and intermods are much suppressed,
and sure, the THD reduces along with IMD.

Some ppl may not initially like the triode sound if the pentode with FB gave
increased bass and treble due a
speakers higher Z below 100Hz and above 500Hz, and this was the case in old
radios,
where the FB was omitted not only to save having to have another tube for the
extra
open loop gain, but to allow the high pentode Ra to compensate the miserable F
response
from the AF detector of the radio, typically 150hz to 2 kHz.
But with hi-fi speakers powered by current sources, which is what a pentode amo
is without its GNFB,
the outcome is a bit tricky indeed.




Of course, before you even get there, you notice that in the trioded
pentode, the THD is lower than in the other two modes (pentode, UL) at
any (low) level of NFB. It is difficult not to conclude that the
effective removal of the pentode's screen grid adds additional NFB
which works in some internal way. It is equally difficult to see (and
hear) the different result of this internal NFB and not to conclude
that it works differently from external feedback.


I have posulated that the triode FB works along paths which act on a 3/2
voltage to current rule.
But where very small changes level occur, the changes in THD are virtually
linear because
one acts along what is such a slight amount of bend in the Ra curves.

When plotting the THD for a given class A amp on linear voltage output
versus THD % scales the THD rises slightly faster than a straight line.
So a given amp may make 5% at 20Vrms into a load,
and 2% at 10V.
One might draw a curve through the 0.0V and the 10v and 20V points and find
that's the average for several samples of that amp.
But wide variations in THD occur between samples; tubes are not always matched.

In Quad II samples i have worked on with older tubes it isn't unusual to find
5 times the rated data THD. Swapping positions of the KT66 and or the EF86
can drastically reduce the THD.
Usually they measure a whole lot better when all R&C are replaced,
but still its worth final swapping of known healthy tubes to get the
THD to measure low; and voila, usually the sound is blameless
while every effort has been made to accomodate the imperfections of the items
within the system.

Class AB usually gives a slowly rising THD profile at first which is virtually
the same as full class A, but when the threshold of AB commences the THD rises
much more rapidly,
and graphs of THD with kinks showing the THD increases rapidly with AB action.
pentode amps are worst in this regard because their gain is prportional to
load,,
since gain = gm x RL, and RL reduces to half the class A load ( or to 1/4 RLa-a
) when one tube cuts off.
Triode gm tends to rise and Ra get lower with increasing anode current so
the AB transition produces less odd order harmonics; principally less 5H.
The principle reason why PP triode output tubes in class A are so linear up to
clipping
where 1% THD is not uncommon is that the decline in gm with lessening Ia is
about equal to the increase in
gm with increasing Ia.
The actual load seen by one tube of a PP pair affects the load seen by the
other, and in fact the loads
are curved lines for each tube.

The PP amplifier is so inherently linear and majestically simple that it has
stayed in favour
for all these years............

But its hard to get a PNP transistor to act just like its NPN companion.
They just don't come in twin pairs; more like distant cousins.




Thus my fear that, if you use any form of external feedback to make the
triode and the pentode "electrically equivalent", you will disadvantage
the pentode because the makeup of its harmonics will be adverse *and
will be heard by the panel*.


This is the fundemental problem with comparisons of pentode with loop FB
and triodes, arranged for the same Ra.

However, I have used CFB in my SE35, and with screens bypassed to 0V
and with Eg2 much lower than Ea to minimise Ig2, and got only about 1.5% THD
without
GNFB at 35 watts from a quad of 6CA7.
With such a small amount of 2H at the output stage, it was easy to cancel it by
the
triode driver stage without setting up the driver with an adverse load to
deliberately
create 2H that will cancel in the output stage.
The amp is designed to give maximal THD cancelations in the 4 to 6 ohm load
range
and the benefits seem real sonically during the tests I have done with SEUL
amps using
13EI for a comparison.
I only had to apply a small amount of GNFB in the SE35 to "complete the
picture".
The owner now uses NOS EL34 instead of the Sovtek or EH6CA7,
and perhaps the harmonics produced are even more benign than they were
when supplied with the Russian 6CA7.



I don't actually see any alternative way
which won't turn the pentode into a triode, which defeats the purpose
of a straight-up challenge, so I think you and Patrick are on a wild
goose chase. But that has never stopped us speculating before!


One can only compare two different things to be more aware how each works.

I sometimes wonder what the folks on different planets in the many universes
out there thought when they
discovered thermionic emission in vacuum tubes, and farnarcled around with 2
electrodes, then 3 electrodes,
then 4, then 5, then 7 then 9..............
And we can't advise those who have not yet discovered tubes, and them out there
can't advise us
of what to look out for next.

We are profoundly alone so far, scratching at the surface of the very hugely
unknown.............

Patrick Turner.



Regards,

John Byrns


These, incidentally, are the same test results I interpret as meaning
that there is no such thing as an SE sound, that what we hear which so
appeals is a Class A ZNFB or very low NFB sonic signature. People just
confuse Class A with SE because only a tiny, tiny minority even of the
ultrafidelista have ever heard pure Class A PP amp.

HTH.

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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Henry Pasternack Henry Pasternack is offline
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Default Henry Pasternack's Norton triode model???

"Andre Jute" wrote in message oups.com...
[Deleted]


Typos are a nuisance, but there's enough context in the rest of the paragraph to
figure out exactly what I mean. The only thing attacking me personally shows
is that you have nothing worthwhile to say.

A hundred years ago this subject was cutting edge physics. Most readers don't
have the background to follow the arguments. I know you don't.

If you want to quibble over details, be my guest. I entered the discussion to
respond to Patrick, not to discredit you -- you take care of that on your own.

I feel sorry for Phil, who tried hard to make a positive contribution, spoke his
mind, and got a heap of trash talk from you in return. I would say you ought
to be ashamed of yourself, Andre, but I know you're not capable of it.

I didn't invite your commentary and I'm not interested in your sleazy opinion.

Go away.

-Henry


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Peter Wieck Peter Wieck is offline
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Default Was CFB and UL really specifically intended to combat NFB recombinants? was Explanation still required for triode superiority


Andrew Jute McCoy posited:

One of the really irritating things on the usenet is when you write a
long, detailed post full of facts and opinions -- and find everyone so
much in agreement with you that no one replies.


Far more likely is that no one would dignify the actual lies (your
"facts") or the unsupported posturing (your "opinions") with a reply. I
have been following the actual discussions (with some difficulty) and
the numbers (with some care), and writing only for myself find your
diversions at the very least ignorant, far more typically ignorant,
wrong and diversionary. Sock-puppets are excepted, of course, and may
be expected to chime in momentarily.

For the record, when you express opinion _without_ judgement on others,
eschew the self-pity *and* the arrogance and generally act as a
participant rather than King Rat, I leave you entirely alone. Also, for
the record, note that there is quite a bit of good science, good lore
and good discussion going on here entirely without you, even in this
thread started by you (for which I must be grateful however distasteful
that might be), no thanks to you.

You are 61 years old, and by your self-designed resume have presumably
done it all from dodging assassin's bullets through participating in
and completing the Iron Butt Rally on a self-designed bicycle (
http://www.ironbuttrally.com/IBR/default.cfm ). But you still have a
great deal to learn, not the least of which is humility.

You lie as actual human beings breath.

Peter Wieck
Wyncote, PA



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Ian Iveson Ian Iveson is offline
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Default Henry Pasternack's Norton triode model???

Chris Hornbeck wrote

...so Ia=k*Vak^3/2, with k some geometrically determined
: constant.
:

better formulated as: so, by induction, we know Ia is proportional
to Vak^3/2,
the multiplier k being dependent on geometry and cathode emission


This is actually the approximation for a diode, but the
form for a triode is similar.

Please note that these are approximations. Put another way,
k is not constant, and not linear. It's the k part
that's interesting.



Perveance is largely dependent on heater power, for a given type of
cathode, AFAIR from discussions long ago.

From a practical point of view, I have asked a few times about how I
might take valve ageing into account in my (Duncan Munro's, as nearly
all are) models. One might assume that any decent model should need to
know what kind of life the valve has suffered?

For the moment, I just vary perveance.

It would be nice to sensibly discuss Duncan's most recent model, and
especially to transfer its grid model to his pentode. I wonder to what
extent reducing heater current has the same effect as ageing?

Unfortunately Duncan has gone very quiet, and has withdrawn the
documents describing the derivation of his models.

No-one has even tried, AFAIK, to capture the lumpiness of typical real
valve characteristics...the unevenness that, for any particular valve,
may result in sweet spots. I haven't seen a tetrode kink either,
AFAIR.

All the extra bits added to Child-Langmuir by the more sophisticated
SPICE models are just curve manipulation and bodging. I can't find
much relating them to the physical reality, except approximately
similar behaviour.

As for delay, I suspect that the kind of periods involved in
propogating electron flows in a valve are too short for SPICE to
contemplate. Very few amateurs have access to an alternative modeling
environment, so if it's not SPICE its not much use.

Where we are now, for all practical purposes, is likely to be the end
of the story.

cheers, Ian


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Patrick Turner Patrick Turner is offline
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Default Was CFB and UL really specifically intended to combat NFB



Andre Jute wrote:

One of the really irritating things on the usenet is when you write a
long, detailed post full of facts and opinions -- and find everyone so
much in agreement with you that no one replies. It feels like you're
out in a vacuum somewhere, whereas in fact everyone is just sitting
there nodding wisely, saying, "I knowed that," and not posting a
response because they have nothing to disagree with or add. (For the
non-Anglophones, "I knowed that" is not bad English but a schoolboy
joke.) Patrick must feel like that after his two recent long, detailed
posts full of relevant numbers. I especially enjoyed the historical
references, and sure, I agree, the EF86 is a wonderful little pentode.


The doubters of NFB in triodes have ignored me well because when cornered they
know they really cannot support their position on NFB with any proof.
Ian even went beserk and said there wasn't any NFB in triodes, then said today there
was NFB in everything,
so in so many cases where these guys have not a clue they turn around and say
everything is nothing, and nothing is everything to somehow convince us all of how
wise they are about something
and they use lotsa jargon, but I see them coming, and going,
and if they'd stay gone so I won't have to address the weaknesses in their arguments.

But those who try to concentrate on tubes here are a diminishing crew.



But the only question I want to raise on two whole long posts from
Patrick is one so tangential that it needs a subthread of its own.

Yo, Patrick: you say that the inventors of CFB and UL *intended* by
their inventions to get all the advantages of the triode, including
specifically the advantageous harmonic distribution, together with most
of the power of the pentode. Can you cite any documentary proof of a
deliberate intention with reference to harmonic proportions at this
early date, say the late forties or early fifties? Or is your remark
the result of hindsight brought on by your own, much more recent
observations, and simply reflected back upon those guys -- IOW am I
just reading too much into your statement?


I have first to give credit to those who deserve it amoung the pioneers
of better tube audio gear and who actually did worry their brains to peices over
distortion and noise in kit they thought might sell OK.

I'd have to nominate DTN Williamson and Peter Walker.
After having tried dozens of ways of hooking up multigrids in output stages
I always come back to the Quad II Acoustical connection.

Its neither UL nor is it beam or pentode with local NFB in the output stage.
So why not when surely the two guys could have settled for the cheapest option
of high power with triode distortions, ie, UL?
Harold Leak settled quickly for UL; just adding two taps made his amps
much more saleable.
I think Walker must have known that his Acoustical did the business the best.
And if you examine it, with 10% CFB, there is CFB applied in TWO ways around the
KT66. if you examine the actual Quad II circuit,
there will be say +0.9D volts of THD at the anode.
Therefore -0.1D will exist at the cathode. This -0.1Dv appears
as an effective +0.1Dv between g1 and k so it is amplified A times to appear at the
anode
as -2Dv if we were to agree the gain of the output stage between Vgk to anode was
-20.
-2Dv is subtracting from the 3Dv that would be there were there no FB at all.
But it ain't that simple.
The -0.1Dv also exists between k and g2, and effectively the g2 is going +0.1Dv with
respect to
k similarly to the g1 to k case.
The screen transconductance creates some gain and an additional correction signal
is created in the anode current so augment the correction created around the g1
circuit.
The math on this is quite daunting, but the concept is there for our understanding.
The applied NFB around the g2 acts slightly differently to the g1 circuit in that
the tube is tending to be like a triode because of its relative total voltages.

If a KT66 is set up with a simple 20% UL taps, the beam distortion characteristics
change
towards triode substantially.
Applying the CFB to both g1 and g2 preserves the partial triodisation spectra
but because most of the effectiveness of the CFB is around the g1 circuit,
you get the output stage tubes to operate about like trioded KT66 but without the
limitations
of the triode due to the restriction of anode swings due to grid current.

I suspect Walker would have tried to use CFB with separate bypassing of each g2 of
each KT66 to
that tubes's cathode; this would have been dead easy with say 3.3k series R and a
47uF electro,
and thus the output stage could have been true beam tetrode with 10% CFB, but then
the
the spectra of the finished output stage would have the more complex spectra of
pentode thd
left intact, but just reduced perhaps by 12dB.
( certainly today anyone could bypass each g2 easily to each k in their Quad II amps;
they'd
have to maybe reduce the global FB though ...)
With both g2 taken to a fixed voltage, the open loop gain of the KT66 isn't as great
as the pure beam tetrode
would provide, and the thd reduction with 10% CFB isn't as great but then the
effectively
applied g2 FB made the spectra more acceptable to begin with so the extra reduction
of real beam tet + CFB wasn't needed, so onlt one bypass cap was needed and it could
have the erathy end
taken to 0V, and there was no need for two series R and instead a choke as used to
filter the screen supply
well since that's what helps keep the noise from the PS low in Quad II in addition to
the
common mode rejection which operates over most of the F range with ESL57, since
they are so easy to drive because of their mainly high Z between 50Hz and 1 kHz.

In my experiments with far better OPT than Walker settled for in his Quad II
the operation in pure tetrode with FB gave slightly worse looking THD on the CRO.
A decent PP amp should have a nice clean looking 3H tone of THD right up to clipping
without easily seen 2H, or any other jagged wriggles in the distortion wave which
would indicate the presence
of 4,5,6,7,8,9H etc.
if the 3H trace looks like a clean sine wave to the eye, then any other harmonics are

at least 20dB down and if the 3H is at 0.01%, anything else will be at 0.001%
and who is going to tell me they hear the results of say 0.001% of 5H?
But so often there is a mix of 3H and 2H because of
anything between slight and gross tube mis-matches.

In discussions with Neville Thiele in about 1995 when I was learning about all this
he asked me if I'd tried to use CFB with cross coupled screen taps off the anode
windings to give not just
equal g2 signal to k signal but a boost to g2 signal of about twice the k signal, ie,

positive FB applied to the g2.
Positive FB wasn't sneered at in 1955, and there are schematics in RDH4 with positive

series voltage FB to artificially boost the open loop gain of an amp circuit
and thus increase the applied NFB which depends on gain and thus reduce the N&D and
Rout.
Anyway, I didn't see the point of trying Neville's recomendation
that he and his pals farnarcled around with when they were young fellas in 1955;
these guys were mainly number oriented; if it measured well, they'd just do it, and
numbers guided
most audio engineering efforts, and concerns modern audiophiles have about distortion

and using no loop FB were yet to gain any real prominence.
And PFB always seems to reduce the margin of stability of any amp where its used.
I found spectra with pure tetrode with CFB was worse, and could perhaps get more
worse
with PFB, so I left it out.
I did try CFB with UL taps, and I got 0.7% THD at 40 watts with a quad of 6550,
but when i upped the anode supply to 470v for more AB operation and higher power
the Acoustical was better and without the UL taps with CFB the THD went down an
amazing 10 dB
with both g2 taken to a suitable B+ supply, somewhat lower than the anode B+.
The final preferred schematic is that of my 8585 at
http://www.turneraudio.com.au/8585integrated.html
The output stage in the 8585 is about as blameless as one could hope for,
and if I had used triodes to make the same power and had no CFB, it wouldn't measure
any better of have meaningfully lower amounts of spectra.
Maybe Williamson would be happier if I had used a triode output stage, if he were
around to see it,
but the 8585 has enough redeeming features to excuse it from the obligation
of including triode operation in the output stage.
Typically the THD of the 8585 is at negligible levels at normal listening levels
and it does not have an enormous amount of total FB applied.
It is only slightly better measuring than plain UL with 50% taps with which
I have also pleased some customers.

At some point the measurements don't mean much because they are so low, and so
benign.
At below 0.02%, I doubt I have to worry; the sound is then qualified in terms of
dynamics, and realism, preserved warmth, and those other subjectives that the
engineers
insist may flow on from the good numbers, but which audiophiles think may NOT flow on
from good numbers.
Ive heard changes to sound quality just by replacing input tubes in a line stage
preamp
with different brands; the idea that THD affects the sound does not stack up because
when i measured THd it was below 0.01%, and mainly 2H during such tube rolling.
Was it the subtle effect of microphony resonant F of the tubes chosen?
I doubt that because you only get microphony effects with phono and microphone
amplifiers,
unless the chosen tubes were really badly micophonic, and none I have selected have
been.
So there is something inexplicable about tubes.
And in the 1970s ppl in hi-fi mags talked about the sound of various transistors
making a big difference, even though ALL the circuits were drenched in NFB
wheras the triode preamp i fiddled with had zero loop FB. Just what made the
difference
in 1970? maybe it was LSD by 1975...

I cannot point to any particular written material which prooves
that Wlliamson amd Walker understood that UL was better than pure beam with either
shunt FB or series CFB, but I cannot help thinking they must have given
THD and the spectral purity a lot of thought.
What else was there to think about in 1940 to 1955 apart from a terrible world war,
and frightful distortions in all audio gear except in the FB amps they contrived?
There were guys who tried many of the techniques of output stage contrivances
well before they were officially invented by prominent ppl, some of whom
were well off and could afford to patent their ideas.
Just about every single damn connection of OPT to tubes that could be tried
had been tried by 1950 by somebody.

Things got a lot worse for awhile with germanium transistors.
They just applied MORE NFB.
Most consumer electronics continued to be the results of eager
dumbing down efforts by bean counters....
Very few ppl stuck to using their triode amps.
The 1950s and 60s were a regressive period in human history imho.

If we are bright enough to see that history repeats itself, we are more likely
to keep our faith and ignore the BS, and sweep out only what is
definately inferior, and avoid the traps of fads.

Patrick Turner.








TIA.

Andre Jute
Twenty-twenty hindsight

Patrick Turner wrote:
Andre Jute wrote:

John Byrns wrote:

In article .com,
"Andre Jute" wrote:

I'm reading this part of the thread with great pleasure; it reminds me
of the glory days of RAT when high theory was everyday meat on the
table.

There's some confusion here about which tubes we're talking about.
Perhaps I am to blame for it, in phrasing the thread headline too
bluntly as "triode superiority". But the results of tests and my actual
opinion, which comes as no surprise to you, is not the unqualified
"triodes are superior" but that "ZNFB or low NFB Class A1 triodes and
trioded pentodes are superior on the ear of qualified listeners to any
other form of reproduced music". My best amp ever, in the ears of my
test groups of professional performers, is PP EL34 Class A running ZNFB
or less than 6dB of NFB; I usually test it against expensive 300B gear
either of my own decising or commercially available and *behind the
curtain* it usually wins.

Next, the problem with pentode sound is not so much the pentode itself
but the amount of NFB required to get it to deliver its power with any
pretense to quality, the NFB creating recombinant harmonic artifacts
which are very disturbing to qualified listeners. Thus, if we use any
NFB at all in the levelling process, as in the CFB example, the
question is opened up of the recombinant harmonic effects of NFB *which
we are then adding to only one of the contestants*, the pentode, to
disadvantage the pentode yet again.

Hi Andre,

Please cut me a little slack if I have missed something, as I wasn't in
on this thread from the beginning.

The necessary information is spread over many threads and my netsite.

I don't understand your apparent
thesis that the triode is superior, if indeed your "PP EL34 Class A
running ZNFB" is your best amp ever, as judged by your "test groups of
professional performers"?

The headline is a provocative outgrowth of a bad-tempered set of
threads on whether a triode has native or built-in negative feedback. I
have always said that best amp I ever built was the trioded EL34 PP. In
fact I spelt it out earlier in this thread as well, but nobody took the
slightest notice.

Are the EL34s in this amp triode connected
with the screen grids strapped to the plates?

Yes.

If this is the case, the
implication is that an EL34 with the screen tied to the plate makes a
better triode than the 300B used in several of your other amp designs?

Yes. The comparison is ZNFB or very low NFB triode strapped EL34 PP
against SE ZNFB 300B. In level matched tests with a third, usually
solid state placebo amp also behind the curtain, a sophisticated
listening panel will choose the PP EL34 pseudo-triode amp every time.
(The SS amp commonly gets no votes.)

There are complications, in that when you double up the tubes on each,
to compare PSE and PPP, all other factors equal, except that now you
can use better speakers, specifically ESL63, the results get a bit
closer simply because the speakers offer more resolution to a test
panel accustomed to listening to details, and that big broadcasting DHT
like 845 and SV572-xx whip little EL34, but for practical,
level-matched tests at the entry level -- not meaning money, for all
these amps are expensive, but the entry level of very high resolution
-- sure as hell triode strapped PP ZNFB EL34 hold the upper hand. You
have to be in PP 300B at umpteen-eleven times the price, with a lot of
high-ticket high-carriage iron on board, before the natural triodes
make as good a showing as the humble, inexpensive, ultra-versatile
EL34; by then it is clearly no longer a fair test (but then, in terms
of high street hi-fi prices even the base EL34/300B test has only a
tenuous connection to what most people would regard as reality).


I have heard music via a pair of made in HK 18watt Vincent PP amps using two
300B
which to me did all the business really well.

it wasn't an expensive amp in1995, when I used to attend the NSW Audiophile
Society's meetings
to see what other folks got up to.

For PP triodes and 18 watts you need about 400V and 150mA,
and an OPT with about 8k : 8 ohms, and your'e away.
The same PS could be used for a pair of EL34, and get less power, or a pair of
6550 in triode
for maybe slightly more power. But the iron need only be about the same and not
cost a lot'
the cost is mainly in the higher costs of the 300B and perhaps in its needed
pair
of 5V filament supplies.
I personally don't see any point to using EL34 in triode when for such a small
extra outlay
6550 or KT88 in triode could be used and which would have lower Ra-a
and more power which is very much worth that slight extra outlay.





I give you the additional information because we need to be clear that
what I have proved isn't that PP amps are better than SE, merely that
the EL34 is a stonking good tube, especially at the price.


Also don't forget the EL34 replacement called the 6CA7, a beam tetrode, also
an underated tube.
I had to do a minor repair on a 'THD" branded SE guitar amp last week
which had a Russian 6L6GC running with 45 watts of anode dissipation with the
anode only
a tiny bit red in one place. It was fine at 35 watts.
EL34 will glow red with less Pda than this 6L6GC.
So I it seems the humble 6L6GC now made with its actual higher pda capability
well above the
original 22 watt rating could produce good triode power in a PP circuit.



The test
only incidentally pitches a PP against an SE amp; I had long before
this discovered that SE or PP matters not when both are made with
triodes running in Class A and you have a very light or absent hand on
the NFB; what I set out to prove in these later tests with the PP
trioded EL34 was something about Class A sound, and something about the
composition of distortion, and something about the lowest imperceptible
level of loop or anyway additional NFB.


I tried PP EL34 in triode in a pair of Quad II amps for 13 watts with 6db of
global NFB
and the owner said it lacked the sparkling
dynamics of a 10 watt amp using 6GW8 in class AB1 and about 17dB of GNFB.
Only when i went to KT88 in triode with 12 dB of GNFB did the owner say that
the
Quads then sounded as good as the UL amp and that the bonus was a slighty
higher ceiling
because the KT88 in triode with Ea at 400V and fixed bias the amp gave 20 watts
AB1.
There is lots about modding Quad II at
http://www.turneraudio.com.au/quad2powerampmods.html

I conclude from my observations and from what customers tell me that 12dB of
NFB is fine in a
triode PP amp. Nobody I know can tell the difference between
a normal triode amp with 12db of GNFB and the same amp with its screens taken
to UL
taps and with the FB left the same.


You also seem to be saying that the negative feedback that is inherent


in the operation of a triode is not responsible for its superior sound,

On the contrary, it seems to me very likely that the negative feedback
inside a triode is responsible for the quality of its sound. To me it
is a very persuasive argument that to bring a pentode back even partway
towards the silence of a triode you have to use the NFB that was taken
away to make it a pentode!


Well, yes, but impossible....



However, it is clear to me that external forms of NFB, as in loop
feedback, UL, CFB, etc, act differently to the native or internal NFB
of a triode. This is easily seen in comparative harmonic output
analysis of an EL34 amp with a pentode/UL/triode switch and a pot or
switch to alter the amount of loop NFB, as in my T113 "Triple Threat"
PP EL34.


Well indeed there IS a difference in FB transfer between external and triode
internal transfer.

Local or global NFB loops are normally employed in linear mechanisms; ie the
CFB of an OPT with CFB is where
the cathode voltage is magnetically locked to the energy elsewhere generated.
The fed back voltage is exactly the same in spectral content at the cathode as
at the anode'
only the phase is opposite.
The local CFB with screen fully bypassed to cathode acts to reduce all the
spectra of the
pentode without NFB, and most pentodes suffer double digit THD at clipping when
tested
to gain the published data for SE use; 13% THD is about what is quoted, and a
horrible mix compared to
the 5% of the trioded case, with most only 2H.
Note that these figures are for the rated load use stated for the tube;
Loading means a heck of a lot with output tube distortions.
Unloaded, the pentode is abysmally horrible.
But when CFB or external GNFB is added, the higher the load, the higher the
gain
so for a given value of ß, the greater tha amount of NFB applied, so although
the
THD rises as load increases with no NFB, it is limited in rise when a given
amount of NFB is applied.
The triode THD reduces to almost nothing when load value is very high,
indicating
its inmternal FB is maximally effective, similar to the case od the unloaded
pentode with a given amount
of CFB as i calculated in a previous case for the EL34.

When loaded though, the gain of the triode goes lower, and the internally
applied amount of NFB becomes lower
but still present, and the transfer of the NFB becomes maximally affected by
the nonlinear 3/2
voltage effect on Ia.
A similar thing occurs in UL, but intermediate between triode and pentode,
and somewhat unique, ie, different to either triode or pentode.

A UL amp with 43% taps and EL34 may make a maximum of say 32 watts,
and in triode its 14 watts, but the UL amp will have no more THD than the
triode amp at 5 watts,
and be spectrally as clean.
Trouble is the Rout. The UL amp has Rout about = RL, and GNFB must be used to
further reduce Rout.

In the past many makers competed with each other to get the highest possible
amount of GNFB applied around their UL
amps to be able to say they had 0.03% THD at 45 watts.
30db of applied GNFB was not uncommon in top brands using
well made OPT.
Meanwhile all the makers with lesser quality OPTs had to settle for no more
than the standard 20dB
of GNFB and 0.3% THD at clipping for class AB1.
Now 17db is a lot of GNFB around any tube amp.
In actual fact, few could really tell the difference between samples of all the
above
amp recipes at average normal listening levels of 86db, or 1/2 a watt average
to each of two speakers.
Nobody is going to win any prizes for applying more than just enough GNFB
around any tube amp these days.
Sanity has prevailed; we have done away with the uneccessary.

A UL amp with 50% taps and in class A PP with 6550 typically makes 1% THD of
mainly only 3H
at about 30 watts and without GNFB.
At 3 watts, output voltage is 1/3 of clipping, and THD is about 0.2%, and at 1
watt
its THD is about 0.11%, and THD is already so low that it isn't of any concern
and would
not be discernible by 99% of the population.
However, the Rout would seriously colour the sound, depending on the vaguaries
of speaker Z
so if 15dB of NFb were applied, the typical Rout without NFB of about 5 ohms
if the secondary winding was a match for 5 ohms is reduced to about 0.7 ohms.
All is well if the OPT has wide BW to start with and the driver amp is suitably
set up.
people knock UL amps with 6550, but it has been my experience to seriously dent
all the
egos of other makers of amps with triodes and low GNFB with samples of mine in
demonstrations with the
audiophile club, and while using 1/2 the output tube count.

I have nothing against trying to use zero GNFB and rely on just the natural low
Ra of the triode.
But I would say that then one is compelled to use wide BW OPTs, lest the OPT
unecessarily act as a filter,
so don't try an old Leak Point 1 TL12 without its GNB in triode; the OPT has
50mH of leakage inductance!
And one wants low winding loss OPTs, and with a nice high voltage ratio
to give the output tubes a higher than normal AB1 loading.
So when thinking of EL34 in triode I'd be thinking of 10k : 6 ohms OPT ratios,
using Ea = 425V, Ia = at least 50mA.
The Ra-a of the triode = 2.5k, and this is transformed to 1.5 ohms by the OPT Z
ratio
of 1,666:1.
Then one adds the effective winding resistance of say 0.4 ohms at the sec and
you still get
Rout at about 1.9 ohms.
This is one reason why not to use EL34 in triode when 6550, KT88, or KT90
will all give you 1.5 ohms under the same conditions.
But the larger tubes allow a higher safe Ea at the same Ia, and so RLa-a can be
higher,
say 12k : 6 ohms, or 2,000 : 1 so the Ra-a of 1,800 ohms is reduced to only 0.9
ohms,
and plus Rw, Rout = 1.3 ohms. 300B will do slightly better since the Ra is
slightly lower than
any of the larger octal power tubes in triode.
The benefit of having each output tube seeing a class A load of 6k each is that

the THD also is quite low, and negligible at ordinary listening levels.



do you have any clues yet as to exactly what it is that is responsible
for the superior sound of the triode and the triode connected pentode?

Sure. The difference in sound between a triode (natural or screentied)
and a pentode is caused by the different makeup of the harmonics.


Especially the IMD caused by the varying gain with load changes.
In the pentode, these are high, in the triode low, and its a function of the
Ra....


Regardless of the absolute level of distortion, the triode, however
made, has a lower proportion of odd and higher harmonics than the
pentode. It is known that very low percentages of odd and higher
harmonics can cause uneasiness in listeners.


This very true, and when i built a pair of SET 4 watt amps using 2A3
they sounded cleaner than the same power from an EL84 in pentode with global
NFB.
However, I do have a pair of SE amps with EL84 with about 10% CFB and slight
NFB
and these are remarkably triode like, and very listenable.

I think the 2A3 gives the best 4 watts possible out of all devices in the
universe.

It is strong supporting
information that the difference between a good 300B amp and a bad one
can be read in the proportion of 3rd harmonic left on the bad amp (as
you yourself showed in a table when you compared my HVHCHL "Hedonist"
to the distrastrous BobC/LaFevre/Magnequest "Bubbaland" amp roundabout
1998 -- that was a big clue on the way to my present understanding --
thanks!).

The easiest way to prove the importance of the proportions inside the
THD to yourself is to put a pentode/UL/triode switch and an NFB pot on
a pentode amp and to study the makeup of the distortion in each mode at
various levels of NFB including zero NFB. Of course, it took me a bit
longer than a single sentence, because I had to eliminate all the
common factors between the various topologies (I wasted years on AC
balance in PP amps) before I isolated the odd factor and could examine
it closely. There is no other parameter where the change is so striking
and so inexplicable. Even at zero NFB, the third and higher harmonics
fall through the floor when you turn the triode switch on a pentode
amp.


Well, switching that switch from pentode to triode is connecting the triode FB.

Ra falls heaps, the iron distortions and intermods are much suppressed,
and sure, the THD reduces along with IMD.

Some ppl may not initially like the triode sound if the pentode with FB gave
increased bass and treble due a
speakers higher Z below 100Hz and above 500Hz, and this was the case in old
radios,
where the FB was omitted not only to save having to have another tube for the
extra
open loop gain, but to allow the high pentode Ra to compensate the miserable F
response
from the AF detector of the radio, typically 150hz to 2 kHz.
But with hi-fi speakers powered by current sources, which is what a pentode amo
is without its GNFB,
the outcome is a bit tricky indeed.




Of course, before you even get there, you notice that in the trioded
pentode, the THD is lower than in the other two modes (pentode, UL) at
any (low) level of NFB. It is difficult not to conclude that the
effective removal of the pentode's screen grid adds additional NFB
which works in some internal way. It is equally difficult to see (and
hear) the different result of this internal NFB and not to conclude
that it works differently from external feedback.


I have posulated that the triode FB works along paths which act on a 3/2
voltage to current rule.
But where very small changes level occur, the changes in THD are virtually
linear because
one acts along what is such a slight amount of bend in the Ra curves.

When plotting the THD for a given class A amp on linear voltage output
versus THD % scales the THD rises slightly faster than a straight line.
So a given amp may make 5% at 20Vrms into a load,
and 2% at 10V.
One might draw a curve through the 0.0V and the 10v and 20V points and find
that's the average for several samples of that amp.
But wide variations in THD occur between samples; tubes are not always matched.

In Quad II samples i have worked on with older tubes it isn't unusual to find
5 times the rated data THD. Swapping positions of the KT66 and or the EF86
can drastically reduce the THD.
Usually they measure a whole lot better when all R&C are replaced,
but still its worth final swapping of known healthy tubes to get the
THD to measure low; and voila, usually the sound is blameless
while every effort has been made to accomodate the imperfections of the items
within the system.

Class AB usually gives a slowly rising THD profile at first which is virtually
the same as full class A, but when the threshold of AB commences the THD rises
much more rapidly,
and graphs of THD with kinks showing the THD increases rapidly with AB action.
pentode amps are worst in this regard because their gain is prportional to
load,,
since gain = gm x RL, and RL reduces to half the class A load ( or to 1/4 RLa-a
) when one tube cuts off.
Triode gm tends to rise and Ra get lower with increasing anode current so
the AB transition produces less odd order harmonics; principally less 5H.
The principle reason why PP triode output tubes in class A are so linear up to
clipping
where 1% THD is not uncommon is that the decline in gm with lessening Ia is
about equal to the increase in
gm with increasing Ia.
The actual load seen by one tube of a PP pair affects the load seen by the
other, and in fact the loads
are curved lines for each tube.

The PP amplifier is so inherently linear and majestically simple that it has
stayed in favour
for all these years............

But its hard to get a PNP transistor to act just like its NPN companion.
They just don't come in twin pairs; more like distant cousins.




Thus my fear that, if you use any form of external feedback to make the
triode and the pentode "electrically equivalent", you will disadvantage
the pentode because the makeup of its harmonics will be adverse *and
will be heard by the panel*.


This is the fundemental problem with comparisons of pentode with loop FB
and triodes, arranged for the same Ra.

However, I have used CFB in my SE35, and with screens bypassed to 0V
and with Eg2 much lower than Ea to minimise Ig2, and got only about 1.5% THD
without
GNFB at 35 watts from a quad of 6CA7.
With such a small amount of 2H at the output stage, it was easy to cancel it by
the
triode driver stage without setting up the driver with an adverse load to
deliberately
create 2H that will cancel in the output stage.
The amp is designed to give maximal THD cancelations in the 4 to 6 ohm load
range
and the benefits seem real sonically during the tests I have done with SEUL
amps using
13EI for a comparison.
I only had to apply a small amount of GNFB in the SE35 to "complete the
picture".
The owner now uses NOS EL34 instead of the Sovtek or EH6CA7,
and perhaps the harmonics produced are even more benign than they were
when supplied with the Russian 6CA7.



I don't actually see any alternative way
which won't turn the pentode into a triode, which defeats the purpose
of a straight-up challenge, so I think you and Patrick are on a wild
goose chase. But that has never stopped us speculating before!


One can only compare two different things to be more aware how each works.

I sometimes wonder what the folks on different planets in the many universes
out there thought when they
discovered thermionic emission in vacuum tubes, and farnarcled around with 2
electrodes, then 3 electrodes,
then 4, then 5, then 7 then 9..............
And we can't advise those who have not yet discovered tubes, and them out there
can't advise us
of what to look out for next.

We are profoundly alone so far, scratching at the surface of the very hugely
unknown.............

Patrick Turner.



Regards,

John Byrns

These, incidentally, are the same test results I interpret as meaning
that there is no such thing as an SE sound, that what we hear which so
appeals is a Class A ZNFB or very low NFB sonic signature. People just
confuse Class A with SE because only a tiny, tiny minority even of the
ultrafidelista have ever heard pure Class A PP amp.

HTH.

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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Default Henry Pasternack's Norton triode model???

On Thu, 12 Oct 2006 14:51:57 +0200, "Ruud Broens"
wrote:

: This is actually the approximation for a diode, but the
: form for a triode is similar.

actually, it's more general than that, it is applicable to all tubes
under space charge conditions, subject to modification when there are
more influences (such as grids). in a penthode, for instance, the diode
curve comes back for both G1 and G2 voltage vs Ia.


other interesting stuff snipped for bandwidth

Another thing folks who take Terman's introductory college
texts as Gospel is that Child actually is more interesting
in the original (_Phys. Rev._, 32, p.498, 1911 [!} ).

Child includes a term for distance between electrodes that
we always just roll into k because it's outside our control.
But he also specifies certain assumptions:

1) that the electrodes are parallel infinite planes

2) that the plate current is limited only by space charge
(not by emission saturation)

3) that there is no gas within the tube (or at least not
enough to cause retardation of the electrons due to collisions
with gas molecules)

4) that equipotential electrodes are used

5) that the electrons are emitted with zero velocity

6) that the contact potential at the plate is negigible.

Since most of these assumptions are never wholly realized
in actual tubes, the exponent (*always* given without
caveats) generally differs somewhat from 3/2, being
somewhere between 1 and 5/2.

There's a very good description in Eastman _Fundamentals
of Vacuum Tubes_ Third Edition, edited by Terman, 1949,
probably still pretty available, from his famous MIT series.


My thoughts are that interesting real-triode deviations are
largely geometric, ei. from the first assumption above, and
that a realistic triode model must begin in a geometric
rather than an algebraic form.

Much thanks, as always,

Chris Hornbeck
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Default Henry Pasternack's Norton triode model???

On Thu, 12 Oct 2006 16:07:52 GMT, "Ian Iveson"
wrote:

As for delay, I suspect that the kind of periods involved in
propogating electron flows in a valve are too short for SPICE to
contemplate. Very few amateurs have access to an alternative modeling
environment, so if it's not SPICE its not much use.


Delay, if included in an algebraic (including SPICE, etc.)
model that also includes "inherent triode feedback"
would imply some(* ps later maybe) tendency to oscillate.
Maybe that's why it's not included.


Where we are now, for all practical purposes, is likely to be the end
of the story.


And yet, having despaired of the topic and this newsgroup,
and life, the universe, and everything, I've read recent
interesting stuff and despair has faded into...

What's the word?

Much thanks, as always,

Chris Hornbeck
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Default Was CFB and UL really specifically intended to combat NFB recombinants? was Explanation still required for triode superiority

On 12 Oct 2006 07:02:14 -0700, "Andre Jute" wrote:

One of the really irritating things on the usenet is when you write a
long, detailed post full of facts and opinions -- and find everyone so
much in agreement with you that no one replies.


Patrick must feel like that after his two recent long, detailed
posts full of relevant numbers.


I would really, really love to read Patrick, but, lacking
an editor, sadly I cannot. Life is too brief, and he seems
not to care if I live long enough to read even a single post.

Doubtless good stuff, but inaccessable to me. My loss.


Yo, Patrick: you say that the inventors of CFB and UL *intended* by
their inventions to get all the advantages of the triode, including
specifically the advantageous harmonic distribution, together with most
of the power of the pentode.


If he actually said that, which would be very surprising,
he's incorrect.

JMOHFO, but defensable.

Much thanks, as always,

Chris Hornbeck


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Ruud Broens Ruud Broens is offline
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Default Henry Pasternack's Norton triode model???


"Chris Hornbeck" wrote in message
...
: On Thu, 12 Oct 2006 14:51:57 +0200, "Ruud Broens"
: wrote:
:
: : This is actually the approximation for a diode, but the
: : form for a triode is similar.
:
: actually, it's more general than that, it is applicable to all tubes
: under space charge conditions, subject to modification when there are
: more influences (such as grids). in a penthode, for instance, the diode
: curve comes back for both G1 and G2 voltage vs Ia.
:
: other interesting stuff snipped for bandwidth
:
: Another thing folks who take Terman's introductory college
: texts as Gospel is that Child actually is more interesting
: in the original (_Phys. Rev._, 32, p.498, 1911 [!} ).
:
: Child includes a term for distance between electrodes that
: we always just roll into k because it's outside our control.
: But he also specifies certain assumptions:
:
: 1) that the electrodes are parallel infinite planes
:
: 2) that the plate current is limited only by space charge
: (not by emission saturation)
:
: 3) that there is no gas within the tube (or at least not
: enough to cause retardation of the electrons due to collisions
: with gas molecules)
:
: 4) that equipotential electrodes are used
:
: 5) that the electrons are emitted with zero velocity
:
: 6) that the contact potential at the plate is negigible.
:

he, he forgot to include secundary emission fx ;-)

: Since most of these assumptions are never wholly realized
: in actual tubes, the exponent (*always* given without
: caveats) generally differs somewhat from 3/2, being
: somewhere between 1 and 5/2.
:
larger than ^3/2 you'll have to give me an example of that ;-)

but sure, actual electron emission is more like at some 0.5V 'speed',
the space charge is non uniform, trace gasses will be around,
DH will not have equipotential cathode when DC heated,
etc. etc. - the imperfections of the physical implementation world

: There's a very good description in Eastman _Fundamentals
: of Vacuum Tubes_ Third Edition, edited by Terman, 1949,
: probably still pretty available, from his famous MIT series.
:
:
: My thoughts are that interesting real-triode deviations are
: largely geometric, ei. from the first assumption above, and
: that a realistic triode model must begin in a geometric
: rather than an algebraic form.
:
: Much thanks, as always,
:
: Chris Hornbeck

with computing power now available, it should be possible
to model just about everything to ~perfection~ when the
physical sizes, shapes, chemical compositions, heat delivered
are known accurately. still, that 's a damn lot of work for
-somewhat better-
(although used -designing new tubes- would give it a whole
different meaning

you got me looking at some triode curves, first one
6BX7, 25V 10 mA, 100V 80 mA perfect ^3/2
then
the Pa 125W, 60W heater massive power triode
GM70, 100V 34 mA, 400V 204 mA
200V 54 mA, 800V 330 mA about ^1.3

btw, running it at 1400V, 80 mA 112W Pa,
will just do 44W SE in a 14K reflected OT,
40 % efficiency (for Stewart and Graham

ECC83 Mazda gave ^1.12 to ^0.97 from 10 to 160V
in general, low current will spoil the "space current
dominates all" approximation quite a bit.

cheers,
Rudy


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Default Henry Pasternack's Norton triode model???

On Fri, 13 Oct 2006 21:35:48 +0200, "Ruud Broens"
wrote:

: Since most of these assumptions are never wholly realized
: in actual tubes, the exponent (*always* given without
: caveats) generally differs somewhat from 3/2, being
: somewhere between 1 and 5/2.
:
larger than ^3/2 you'll have to give me an example of that ;-)


Maybe the most straightforward way to get a large exponent
is by variable grid spacing. An example might be variable-mu
tubes like 6BA6, etc. where nonlinearity is a design goal.


ECC83 Mazda gave ^1.12 to ^0.97 from 10 to 160V
in general, low current will spoil the "space current
dominates all" approximation quite a bit.


Linearity like this requires very careful work getting
tight and equally-spaced grid pitch. The great European
manufacturers knew more than just metallurgy; they could
build very high precision small things long before
modern computer control of everything. The linearity
of Telefunken and some Amperex 12AX7's is pretty amazing.

And probably not duplicable today. Don't know for sure.

Much thanks, as always,

Chris Hornbeck
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Ruud Broens Ruud Broens is offline
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Posts: 190
Default Henry Pasternack's Norton triode model???


"Chris Hornbeck" wrote in message
...
: On Fri, 13 Oct 2006 21:35:48 +0200, "Ruud Broens"
: wrote:
:
: : Since most of these assumptions are never wholly realized
: : in actual tubes, the exponent (*always* given without
: : caveats) generally differs somewhat from 3/2, being
: : somewhere between 1 and 5/2.
: :
: larger than ^3/2 you'll have to give me an example of that ;-)
:
: Maybe the most straightforward way to get a large exponent
: is by variable grid spacing. An example might be variable-mu
: tubes like 6BA6, etc. where nonlinearity is a design goal.
:
:
hmm, that feels somewhat like cheating, but ok.
talking about crazy curves, try to find a DL73 data sheet
penthode, with G2 100V, for all but the 0 Vg1 grid voltage,
going from 10 and 30 V Plate, the current decreases
negative impedance, shouldn't be too hard to make an
oscillator with that :-)
(of course, many tetrodes have this effect, where G2
takes a lot of current , but the DL has it very pronounced)

Rudy
now experimenting with a gridless penthode


: ECC83 Mazda gave ^1.12 to ^0.97 from 10 to 160V
: in general, low current will spoil the "space current
: dominates all" approximation quite a bit.
:
: Linearity like this requires very careful work getting
: tight and equally-spaced grid pitch. The great European
: manufacturers knew more than just metallurgy; they could
: build very high precision small things long before
: modern computer control of everything. The linearity
: of Telefunken and some Amperex 12AX7's is pretty amazing.
:
: And probably not duplicable today. Don't know for sure.
:
: Much thanks, as always,
:
: Chris Hornbeck


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Default Explanation still required for triode superiority

Oops! Been gone a while ...

Well Andre, the idea that I'm a hypocrite is one interpretation, but not
the only one that fits the facts. It is true that I think Henry is right
on this one, and yes, I know he was involved with the magnequest
gangsters, but I honestly have no idea how much, or if he was involved
in anything truly rotten. However, I do know that (1) Henry gave a
logical post on the triode feedback issue, and (2) you responded by
saying he was an asshole, not with a logical response. Regardless of
what someone may or may not have done, the right thing to do now is give
an honest response to the issue being addressed, not attack the guy
personally. Henry raised some legitimate points about my post, and I am
going to admit it when I think someone is right, period.

But really, Andre, do you honestly believe, after seeing my posts, that
I play politics and throw out truth whenever it happens to be convenient
for me?? I doubt it, which is not a good thing. But if you really do,
then I am going to conclude that either it is hard for you to judge
someone's character over the interent, or you occasionally play politics
yourself. Hopefully it's the former.

Phil

Andre Jute wrote:
Phil wrote:

Henry Pasternack wrote:


"Phil" wrote in message ...


You, Andre, I will answer. Patrick can go **** himself, since he's determined to answer my technical discussion of a subject with
mindless insults and unsupported criticisms.


I politely but firmly demand that you do not respond to or repost standerous
statements made about me. If you have any question about this, please
contact me in person so we can discuss.

-Henry



That's fair enough. I felt uncomfortable about responding to this
anyway, as I see no point to (1) bringing up ancient history, (2)
including you in it, since I was never aware of your involvement in
anything evil, and (3) using the technique of "cutting your opponent to
shreds" given the apparent honesty and intelligence of your responses. I
wasn't exactly sure what to do about it, mind you, but your suggestion
seems like the right thing to do.

Phil



Absolutely amazing. Let's take Phil's hypocrisy step by step:


That's fair enough. I felt uncomfortable about responding to this
anyway,



But you don't feel uncomfortable condemning me by implication and name,
because my name is mentioned above? You're a hypocrite, Phil.

And you don't feel uncomfortable condemning Patrick, an innocent third
party, by implication and name, because *his* name is also mentioned
above? You're a hypocrite, Phil.


as I see no point to (1) bringing up ancient history,



I see. The fact that Henry Pasternack consistently, for several years
on end, committed vicious and immoral acts, and approved publicly of
such acts committed by his associates in the Magnequest Scum, are
irrelevant while Pasternack agrees with you, eh Phil? You're a
hypocrite, Phil.


(2)
including you in it, since I was never aware of your involvement in
anything evil,



The evidence of Pasternack's vicious immorality and consistent lies on
professional matters for personal reasons was clear on the newsgroups,
still stands on the newsgroups, are referred to by me in enough detail
to check them on the Google archive and the Harvard Sound List archive,
and you, Phil, have deliberately chosen not to look, to blind yourself
to the fact that Pasternack lies on professional matters. You're a
hypocrite, Phil.


and (3) using the technique of "cutting your opponent to
shreds" given the apparent honesty and intelligence of your responses.



English translation: Phil says, "The only people who are sincere,
honest and intelligent are those who agree with me." You're a
hypocrite, Phil.

The phrase "cutting your opponent to shreds" is itself a dishonest
polemical device. Of course honest people will cut a dishonest, vicious
piece of scum like Pasternack to shreds. You're not only a hypocrite,
Phil, you are dishonest in argument, as we saw in your abuse of
Patrick, and again in this post of yours. Crows of a dishonest feather
flock together. You belong with Pasternack.


I
wasn't exactly sure what to do about it, mind you, but your suggestion
seems like the right thing to do.



English translation: Phil says, "I, Phil, see electronics as a
popularity contest. If Pasternack agrees with me he is always right,
regardless of his history of lying on electronics, regardless of his
proven history of making electronic statements in furtherance of his
personal vendettas."

Below my signature is the evidence of Pasternack's professional
unreliabity and personal viciousness that you refuse to consider. That
is only a sample, of course; a hundred times that much lies in the
archives.

You're a hypocrite, Phil, and you're dishonest. I had hopes for you.
Too bad. Flick.

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:
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

"Phil" wrote in message ...
[Deleted]


I will ask you once again, and I mean it seriously, not to repost these libelous
statements.

If you want to discuss the matter privately, post your email address in a spam-
proof way and I will contact you.



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