[Andre Jute]

Prune wrote:

"Andre Jute" wrote Our legislators managed to criminalize fox-hunting and smoking; when
they will get off their collective fat arse and criminalize negative
feedback? It is clearly consumed only by undesirables.

LOL! Still, listening to stuff with limited amount of NFB in an amp that
has sufficient slew rate doesn't sound bad to my ears. But now there are
all sorts of alternatives like predistortion, using devices with inverse
nonlinearities, Hawksford error correction (feed back and/or forward the
error signal only instead of the whole signal), etc., so you can still get
low distortion without it.

I've dealt with slew rate as a separate matter in another thread.

You definitely have to keep perspective with NFB. I have no objection
to lesser designers using NFB in their amps to cover up their errors.
Solid state is a complete error, which accounts for why it is only
possible to implement with oodles of NFB. My best amp ever, the T113
EL34 triode-linked PP, in the original design had variable feedback but
hardly anyone bothered to build it in and now it isn't even on my own
T113.

Planned distortion cancellation is a chimera. Like NFB, it would not be
required if people would stop hogging tubes out to the ends of the
possible, impossible and totally impossible swing. A tube operated over
only a short part of its transfer curve is the most linear device known
to man.

Anything that requires NFB is by definition a bodge. You know the old
joke about the tailor fitting up an impressionable customer?

****
KISS 123
*****
The customer complained that his new suit didn't fit. 'The sleeves are
too short,' he said to the tailor.

'Yes sir,' said the tailor, 'but if you hold your arm just so, at an
angle as if you're drinking tea with your auntie, it will show just the
right amount of cuff.'

The customer tried it. The tailor was right! 'But what about the other
sleeve? It is definitely too short.'

'Just lower your shoulder, sir. Yes, yes, a little more. Put your foot
out so you can lower your shoulder a little more still. Bend your knee.
Yes, that's it. See how beautifully your suitcoat now fits?'

The customer had to admit the tailor was right. 'Wow. But now the leg
of the pants is all twisted around.'

'That's easily fixed,' said the tailor. 'Just point your other toe
westward, sir, and look over your shoulder to where I am holding up the
hand mirror. See? Doesn't that fit beautifully?'

'Yes,' the customer said doubtfully, 'but-'

'Now would sir like to wear his brilliant new suit or shall we wrap
it?'

The customer was too intimidated to argue. He walked out into the
street in his new suit, his arm crooked as if he were drinking tea, his
other shoulder well down over a bent knee with his foot out to the
side, his other foot pointing westwards, his head twisted back between
hunched shoulders as if complaining to God about a cruel fate.

Behind him he heard a boy say to his father. 'Oh, Daddy, look at the
poor twisted cripple.'

'Hush,' the father said. 'Be grateful the poor man found such a
brilliant tailor.'

****

The Ultrafidelista view of Negative Feedback

by Andre Jute

Negative feedback is the paradigm of modern electronic design. It is
mother's milk to an electronics engineer. He learns to say '100dB of
NFB,' in his sleep before he finishes his first week at the most humble
polytechnic. At the great institutions the professor of feedback is the
most honoured man in the department. In Massachusetts and Minnesota the
feedback guru is the most honoured man on the entire campus, equal in
stature to the football coach. When a guru of transistor high fidelity
(and some in tubes) says, 'I studied under Ron,' one doesn't have to
ask which Ron, one just knows it is the holy name of the prophet of
feedback from the Midwest.

Before I even finished the design of the KISS 300B it was forcefully
suggested by a wannabe guru that with only 50dB more gain (about seven
times as much as is likely to be in the actual design) I can apply 50dB
of negative feedback to linearize my amplifier.

Negative feedback, shorthanded as NFB, is the instant response of the
audio engineering fraternity to all ills, real, perceived,
non-existent. They don't even ask if there is a problem, they swing the
club of NFB regardless. NFB has become a reflex axiom of mainstream
audio design. An audio engineer with his negative feedback is like a
policeman who runs out into the street with his stick and starts
beating a confession out of the first housewife he sees. The difference
is that the policeman is relieved of duty to await punishment and the
audio engineer gets away with it. In the case of the policeman it is
unacceptable behaviour, in the case of the audio engineer so much the
expected norm that no one except the ultrafidelista notice. I guess
that if one in ten million audio amplifiers does not have negative
feedback added, it will be a lot...

No one asked if my KISS Amp requires linearization. The presumption by
all except those already of the ultrafidelista persuasion was that I
would welcome suggestions about A Good Thing.

In the face of such overwhelming acceptance by qualified engineers, why
do we as ultrafidelista not take the same easy path of negative
feedback? Especially considering that superficially NFB is easy to
understand and apply.

How does negative feedback work?

Negative feedback is simply a negative voltage fed back from the output
to the input amplifying device to offset part of the harmonic
distortion which is present as a positive voltage. It costs nothing
except a loss of gain and a few side effects such as phase shift and
possible instability which are well known in the mathematical
literature and more or less easily guarded against depending on the
level of NFB.

'Wow!' those meeting NFB for the first time will now say, 'Something
for free! I'll grab some of that for my amp.' Hey, I said it, and I am
a professional intellectual, by definition an infinite skeptic. NFB is
a thing of beauty that will draw you in. It is like an electronic
Marxism which admits of no contrary arguments because it has subsumed
them all into The Holy Measurements. To question The Measurements is to
commit heresy. You need to be of strong mind to resist the
blandishments of such a universal panacea and of strong stomach to
withstand the hysterical assaults of the lesser engineers defending
their holy grail. (And when you do get hold of a superior engineer to
explain NFB to you, you need to be high-domed indeed because suddenly
NFB can turn very intricate.)

Unfortunately NFB doesn't come without a price. It levies a cruel
charge on the perceived quality of the sound. Negative feedback is what
gives all those 'blameless' transistor and big PP tube amps their
chillingly unnatural sound.

Then how did NFB come to be such a panacea in amplifier design?

Your guess is as good as mine. Hi-fi design is not prestige work for
engineers, or highly paid. The most talented and best qualified
engineers go into automobiles or military hardware or big construction
projects or computer design. The left-overs design amplifiers in the
time they have to spare from writing up specs for requesting a CE mark
for a new electric kettle. Lemmings storming en masse over a cliff come
to mind; such people don't see the necessity of original thought, or
have the mental equipment for it. The exceptions to this rule are
normally audio enthusiasts in charge of their own small audio
manufactories with niche markets; those who grow larger from this base
follow the mainstream mantra of "mo' NFB give lowa' THD" because the
marketing channels demand it from them if they wish to grow. At this
point they usually cease to offer anything different, only the
exclusivity of a very high price. (I know, because a sub-board I
designed for a supplier to the trade turns up in so many very expensive
amps with so many different big names neatly silkscreened on it... it
strikes me as the sort of detail a real designer, as distinct from a
marketer, would take under his own control.) Those very few makers who
will sell you an ultrafi amp without any NFB operate even tinier shops,
usually one man and a cat, just hanging on.

The mechanism by which NFB wrecks your sound

Negative feedback at first acquaintance sounds good enough to take to
bed and cuddle. It isn't. It isn't even as simple as a superficial
acquaintance may suggest. Follow the steps with me, from the theory as
she is received to what arrives at your brain as music:

1. In theory NFB reduces all harmonic distortion equally, without
discrimination. Strictly in theory it does not reshape harmonic
distortion by reducing the most objectionable third and higher order
odd harmonic distortion to a greater extent than the relatively
harmless 2nd harmonic. Thus NFB at its theoretically most benign is
already useless in terms of psychoacoustics, as will become clear at
point 4. If you disregard psychoacoustics, as many audio engineers do,
NFB is brilliant in reducing total harmonic distortion to a number as
tiny as you want. You just pile on more NFB.

2. In real life, as distinct from simplified theory, NFB adds artifacts
of its own. Remember, it is a loop. The signal starts at the input and
is amplified by devices until it reaches the output. From the output a
part of the signal called the negative feedback is fed back to the
input. Here a loop is completed and the combination, less distorted,
reaches the output again, a part of the combination is fed back,
endlessly. The artifacts we want to consider here are created by the
fed-back residue of harmonic distortions adding to both the fundamental
and the distortions already created by the amplifier, then some portion
of the sum of the original and the feedback distortion is fed back
again and added on, until the ooh-ah bird flies up its own fundament.
It looks marginally less disgusting as a recursive mathematical formula
with lots of nested parenthetical parcels of noise being loaded onto
your music. But it is a monkey on the back of your sound, with a
smaller monkey on the back of the first monkey, a still smaller monkey
on the back of the second monkey, and so on ad infinitum. These
additive artifacts are all higher harmonics and the more dominant ones
are all odd. Suppose, for the sake of simplicity, a superbly designed
ultrafidelista amp with some second harmonic and zero odd harmonics
before NFB. Add NFB and the second harmonic will be lowered but the
recombinant new loop now contains newly added intermodulation effects
between the fundamental and the residual second harmonic, and that is
third harmonic. In the next cycle a small but nasty dose of fifth
harmonic that wasn't there before is added by interaction between the
still residual second harmonic and reduced newly added third harmonic.
In short, the artifacts NFB adds to the distortion mix are all of the
most harmful kind. But, say the proponents of NFB, so what? Every time
the loop cycles the added artifacts are smaller, even if there are more
of them... The whole affair starts to smell of trying to argue with a
Marxist who simply declares any inconvenient truth 'an anomaly'. (If
this sounds like a mess from which you should run a mile, you have come
to the right conclusion. Start running now. It gets worse.)

3. We thus arrive at a situation where distortion has been lowered
by NFB but where the most disturbing odd harmonic distortions are still
present to some measure, with the added disadvantage that new and
extremely disturbing artifacts of higher harmonic distortions have been
created by the very process of using negative feedback to lower
distortion. Regardless of the absolute level of THD, or the volume
setting, the mix of harmonics has been adversely affected and now
includes a higher proportion of third and higher harmonics than before
NFB. Let me say that again: after NFB, third and higher harmonics will
make up a greater part of the distortion than before.

4. Low volume levels perforce account for 99 per cent of audiophile
listening because we all have families or neighbours, and we would like
to keep our ears. Unfortunately for the lowest common denominator of
hi-fi designer, the one who specifies NFB as a conditioned response
much like Pavlov's dogs slavered when the bell rang, human physiology
and psycho-acoustic response is such that odd harmonics are
disproportionately more disturbing at lower than at higher listening
levels. This inescapable effect is independent of definition of
'listening level.' At the 110dB in-room SPL (only 14dB louder than an
automatic riveter!) advocated by the already deaf Transient Overload
Elite known on newsgroups as the Borg, this poisonous concoction of
original distortions and NFB recombinant artifacts will be least
disturbing (and soon not heard at all!). At any lower level perceived
interference of this harmonics cocktail with the music will increase in
inverse proportion to the volume level. At low volume levels the
artifacts generated by NFB will by their nature as higher harmonic
distortions be disproportionately far more disturbing. At these normal
listening levels 0.75 per cent of second harmonic distortion may be
below the threshhold of perception for sophisticated listeners, whereas
tiny amounts of third and higher odd harmonic distortions grate.

And they still use Negative Feedback? Are they stupid?

No, they are not stupid. Most of them march to the drum of a cost
accountant on whom we wouldn't spit if he were alight. NFB is as cheap
in money terms as it is expensive in terms of perceived quality of
music. We shall come to those who claim to be sympathetic to
high-fidelity but insist on devices which do not work without NFB, who
have another devious answer. Here, meanwhile, for you to keep in mind,
is a single-sentence summary of a complicated interdisciplinary
argument:
The case against NFB is that for 99 per cent of listening the NFB cure
is worse than the disease.

But surely we don't have to do anything so stupid?

It follows from the argument above that ultrafidelista should choose an
intrinsically linear topology and device which does not require added
negative feedback to 'linearize' the output. The intrinsically linear
device is the thermionic tube in either its triode form or as a pentode
hogtied to work as a triode, which can be a most pleasing alternative
both economically and sonically. The topology is often single-ended
operation, chosen also for several other reasons described elsewhere in
these articles, including KISS; if the chosen topology is push-pull
operation, which is more difficult but far from impossible to arrange
without NFB, operation should be specified as Class A1. Inside the
argued case above lies too the overwhelming reason to accept the
potential small disadvantage that may accompany the preferred topology
in comparison to the discarded alternatives. The disadvantage is of
course the potential for a residual second harmonic that measures high
by transistor or NFB tube standards. (Note the word potential. With a
conservatively designed DHT amp the potential problem should not
arise.)

The ultrafidelista, who are as keen on silent amps as anyone else,
accept this small potential difficulty because it is the lesser evil
compared to NFB. Unbelievers (largely unwashed, according to reports)
sneer that ultrafidelista like this approach because of the 'added
euphonics', which is bow-wow techie talk for the warmth a big chunk of
second harmonic lays on a zero negative feedback single-ended
amplifier. But competent design can easily reduce the level of second
harmonic to below the level of perception without the need for NFB and
its deleterious after-effects. In any event, it is your amplifier. You
paid for it. You have a right to tune it as you please. The key thing
is to get rid of NFB and to understand why you did it.

Can we prove any of this scientifically?

We have already. All of this is the technical subtext to my longtime
contention that what the ultrafidelista hear and love is not a directly
heated triode sound as is claimed by many enthusiasts but a Class A1,
ZNFB sound. (Admittedly, as we have seen above, the right sound is
virtually guaranteed with a ZNFB DHT SE amp of conservative provenance
but may have to be developed the hard way with more economical or
higher-power contenders.) In comparative ABX tests conducted over a
number of years, I found that professional musicians, certified golden
ears, choose the triode-linked Class A1 PP ZNFB EL34 whenever it is
present in the test over all other contenders including SE 300B and
'blameless' high-NFB silicon.

Science also proceeds by pure reason. Ultrafidelista have long doubted
whether what engineers insist we measure (the absolute level of
distortion, THD) predicts success in audio gear. This is the full
circle, because I have just proven by logical, individually uncontested
steps that what matters, once a certain modest level of silence is
assured to an amplifier, is not the absolute level of disharmonics but
their composition. The same proof demonstrates that a more beneficial
distribution follows instantly from doing without NFB.

But transistor amps won't work at all without NFB!

That is not our problem. Those who choose inefficient speakers and
consequently are forced to accept monstrous amps made possible only by
gigadeciBels of NFB, will receive our sympathy - and the music they
deserve.

Engineering hangers-on of transistor attempts at high fidelity, where
the measure of success is vanishing THD rather than sonic hedonism,
pretend to be enthusiasts for NFB. To make it work for them, they have
attempted to change the rules so that we won't hear what their
treasured NFB does to our sound. They sneer that low level listening,
which 99 per cent of us prefer and where NFB does most to wreck the
sound, is 'easy listening' and therefore not permissible. According to
them we should all be forced to listen at the high volume level which
suits NFB amps, which they call 'realistic'. This is a contemptible
circular argument, only too characteristic of a fascist mentality in a
part of the audiophile spectrum which wants to prescribe their arid
vision without regard for our enjoyment.

We can recommend a good tailor to them. It hurts every time you wear
his suit. No pain, no gain, fellers!

In summary

Almost everyone listens at low level most of the time. NFB wrecks
everybody's sound at all levels but most wretchedly at normal listening
levels. We started out with a contemptible circular argument and we
have met another along the way. We can now put both in context:

An 'engineer' who designs an amplifier which does not work perfectly
without negative feedback is like a tailor cutting the suit
incompetently and then demanding that you walk like a cripple to make
it fit, so that everyone can admire the brilliance of your tailor.

Negative feedback is a bodge. That is why it is despicable to the
ultrafidelista.

THE VOLTAGES IN THIS AMP WILL KILL YOU.
GET EXPERIENCED SUPERVISION IF IT IS YOUR FIRST TUBE AMP

All text and illustration is Copyright © Andre Jute 2001, 2004
and may not be reproduced except in the thread KISS xxx on
rec.audio.tubes

-----------
Part of 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

[Patrick Turner]

You definitely have to keep perspective with NFB. I have no objection
to lesser designers using NFB in their amps to cover up their errors.
Solid state is a complete error, which accounts for why it is only
possible to implement with oodles of NFB. My best amp ever, the T113
EL34 triode-linked PP, in the original design had variable feedback but
hardly anyone bothered to build it in and now it isn't even on my own
T113.

Planned distortion cancellation is a chimera. Like NFB, it would not be
required if people would stop hogging tubes out to the ends of the
possible, impossible and totally impossible swing. A tube operated over
only a short part of its transfer curve is the most linear device known
to man.

Anything that requires NFB is by definition a bodge. You know the old
joke about the tailor fitting up an impressionable customer?

But one cannot avoid even unplanned distortion cancellations.
In just about all SET amps the SET driving the output SET has 2H that cancels the 2H of the output tube,
and with such tubes as the 845, the THD approaches 5% of mainly 2H at 25 watts and
with about 110Vrms applied to its grid, so with say an EL34 in triode as the driver
then this driver will produce about 3% 2H at 110Vrms which will cancel much of the 845 distortion
to reduce it to about 2%.
At 1 watt or less where such amps are to be used mostly, there is about 20Vrms needed at the 845 grid
and considerable 2H cancellation still occurs to reduce the thd to well under 1%
with the natural trickery offered by cascading triodes.
The 845 has such low Ra that the damping factor is fine with no loop NFB.
With an EL34 driver, the THD is also quite low enough and beautiful sound results,
and the low Ra results in wide bandwidth and low transformer distortions.
The 25 watt ceiling allows enough dynamic range and bob is your uncle, gertrude your aunt, sit back enjoy
and don't worry what might be done with silly con.
But one does have to make a nice power supply since there is no loop NFB to
ensure the noise is reduced by that method.

Patrick Turner.

[Trevor Wilson]

"Andre Jute" wrote in message
oups.com...
Prune wrote:

"Andre Jute" wrote Our legislators managed to
criminalize fox-hunting and smoking; when
they will get off their collective fat arse and criminalize negative
feedback? It is clearly consumed only by undesirables.

LOL! Still, listening to stuff with limited amount of NFB in an amp that
has sufficient slew rate doesn't sound bad to my ears. But now there are
all sorts of alternatives like predistortion, using devices with inverse
nonlinearities, Hawksford error correction (feed back and/or forward the
error signal only instead of the whole signal), etc., so you can still get
low distortion without it.

I've dealt with slew rate as a separate matter in another thread.

You definitely have to keep perspective with NFB. I have no objection
to lesser designers using NFB in their amps to cover up their errors.
Solid state is a complete error, which accounts for why it is only
possible to implement with oodles of NFB. My best amp ever, the T113
EL34 triode-linked PP, in the original design had variable feedback but
hardly anyone bothered to build it in and now it isn't even on my own
T113.

Planned distortion cancellation is a chimera. Like NFB, it would not be
required if people would stop hogging tubes out to the ends of the
possible, impossible and totally impossible swing. A tube operated over
only a short part of its transfer curve is the most linear device known
to man.

Anything that requires NFB is by definition a bodge.

**What? like Triodes, with their massive amounts of internal NFB?

As usual, Jute, you are full of it. CORRECTLY applied, NFB can turn a crap
amp into a decent one. INCORRECTLY applied, it can turn a crap amp into a
more crappy one.

BTW: Modern transistors are more linear than even the best Triodes.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

[Prune]

"Trevor Wilson" wrote in
:
BTW: Modern transistors are more linear than even the best Triodes.

This is meaningless unless the specific distortion profile is weighted by
the nonlinear masking effects of the human ear and perceptual mechanism.
I've already pointed out references elsewhere that THD measurements do not
in general correlate with human perception of distortion in blind testing.

[Prune]

"Andre Jute" wrote in
oups.com:

The good thing about Hawksford error correction is exactly that you are not
feeding back the signal but only the residual error. Indeed, EC can be
done as feedforward instead of feedback, in which case there's no recursion
whatsoever. EC essentially makes it possible to improve a given power
stage by using a very accurate low power stage. You can use it whether or
not there is NFB also present. And, though most discussion of it is in
applications to stages without significant gain (emitter/source/cathode
followers or heavily degenerated stages with little gain), it's
generalizable though more difficult to trim properly for stages that do
have significant gain.

[Patrick Turner]

Modern transistors are more linear than even the best Triodes.

You have said this misleading statement before.

Unfortunately for your arguments this is not the case with regard to voltage
gain.
Transistors need only a small range of turn on voltage applied between their
base and emitter,
and their gm varies enormously between being on the threshold of turn on of
collector-emitter current and saturation.

Only enormous amounts of externally applied NFB corrects the inherent voltage
non-linearity
of all BJTs where there is substantial current change as in the case of all
power transistors.

Try setting up any bjt in common emitter mode without any emitter resistor and
apply
a voltage from a very low impedance to the base. The bjt is disgustingly non
linear
compared to a triode using no external applied NFB.
Even most pentodes which do not have internal electrostatic NFB like a triode
can easily
out perform a bjt.

I am not here to discuss whether the bjt amp can sound well, or measure well.
Both are known to be possible so it is believed by most folks.

Without external loops of NFB including the emitter follower connection
which is a high amount of applied series voltage NFB, the BJT is a hopeless
voltage amp
unless we try to restrict the current change in the device, and then the gain is

enormous and subject to the perils of the high collector resistance and
circuit slowness due to capacitances, and the non linear input resistances of
other
devices in the signal path.

A class A single bjt voltage amp stage with a single MJE340 with another for a
constant current source
collector load can have a gain of maybe 1,000, or like a pentode with a CCS load
in its anode circuit.
If external loops of shunt NFB are applied around either device, then the
linearity can be quite good for
either device, because for a gain reduction of 100, from 1,000 to 10, the thd is
also reduced about
100 fold.

The linearity is dependant on the NFB applied, and not on the basic VOLTAGE
linearity
of the device without NFB, which for a bjt is relatively poor, and poorest when
considerable
current change occurs in the device.

Patrick Turner.

[Prune]

Patrick, how are FETs in this regard?


Patrick Turner wrote in
:

Modern transistors are more linear than even the best Triodes.

You have said this misleading statement before.

Unfortunately for your arguments this is not the case with regard to
voltage gain.
Transistors need only a small range of turn on voltage applied between
their base and emitter,
and their gm varies enormously between being on the threshold of turn
on of collector-emitter current and saturation.

Only enormous amounts of externally applied NFB corrects the inherent
voltage non-linearity
of all BJTs where there is substantial current change as in the case
of all power transistors.

Try setting up any bjt in common emitter mode without any emitter
resistor and apply
a voltage from a very low impedance to the base. The bjt is
disgustingly non linear
compared to a triode using no external applied NFB.
Even most pentodes which do not have internal electrostatic NFB like a
triode can easily
out perform a bjt.

I am not here to discuss whether the bjt amp can sound well, or
measure well. Both are known to be possible so it is believed by most
folks.

Without external loops of NFB including the emitter follower
connection which is a high amount of applied series voltage NFB, the
BJT is a hopeless voltage amp
unless we try to restrict the current change in the device, and then
the gain is

enormous and subject to the perils of the high collector resistance
and circuit slowness due to capacitances, and the non linear input
resistances of other
devices in the signal path.

A class A single bjt voltage amp stage with a single MJE340 with
another for a constant current source
collector load can have a gain of maybe 1,000, or like a pentode with
a CCS load in its anode circuit.
If external loops of shunt NFB are applied around either device, then
the linearity can be quite good for
either device, because for a gain reduction of 100, from 1,000 to 10,
the thd is also reduced about
100 fold.

The linearity is dependant on the NFB applied, and not on the basic
VOLTAGE linearity
of the device without NFB, which for a bjt is relatively poor, and
poorest when considerable
current change occurs in the device.

Patrick Turner.

[Arny Krueger]

"Patrick Turner" wrote in message
...
Modern transistors are more linear than even the best Triodes.

You have said this misleading statement before.

Unfortunately for your arguments this is not the case with regard to
voltage
gain.
Transistors need only a small range of turn on voltage applied between
their
base and emitter,
and their gm varies enormously between being on the threshold of turn on
of
collector-emitter current and saturation.

It's almost like in Turner-world there are no such things as emitter
resistors.

Only enormous amounts of externally applied NFB corrects the inherent
voltage
non-linearity of all BJTs where there is substantial current change as in
the case of all
power transistors.

It's almost like in Turner-world there are no such things as emitter
followers.

Try setting up any bjt in common emitter mode without any emitter resistor
and
apply a voltage from a very low impedance to the base.

Proving once again that if you do something really stupid, you will get
suboptimal results.

I am not here to discuss whether the bjt amp can sound well, or measure
well.
Both are known to be possible so it is believed by most folks.

It's almost like in Turner-world sonic transparancy is the ultimate sin.

Without external loops of NFB including the emitter follower connection
which is a high amount of applied series voltage NFB, the BJT is a
hopeless
voltage amp unless we try to restrict the current change in the device,
and then the gain is
enormous and subject to the perils of the high collector resistance and
circuit slowness due to capacitances, and the non linear input resistances
of
other devices in the signal path.

Proving once again that if you do something really stupid, you will get
suboptimal results.

Yawn.

[Patrick Turner]

Prune wrote:

Patrick, how are FETs in this regard?

j-fets such as the 2SK369 set up to operate from a 20V supply
with say a 2k RL with 5mA of idle current and without any source resistor
are fairly horrible. You will get about 5% thd at about 5Vrms of output,
and the output is limited to only about 5Vrms.
A 6SN7 with 25k RL and 5mA of idle current will make a heck of a lot more
voltage
output with a 300V supply before you reach 5%.
So the fet THD is about 10 times the amount of the triode for 5Vrms into a
load.
The triode when fitted with a CCS load is maybe 12dB more linear.
The fet with a CCS load will get more linear but you are stuck with gain =
approx 2,000,
instead of 20 as with the 6SN7.
So to use the fet one may use shunt FB to reduce the gain to that of the
triode
and at 5Vrms of output, perhaps the fet is more linear than the triode; its
a function of applied FB and
high open loop gain.

But at 5mV from the fet, the thd is about 0.005%, and quite low enough not
to have to worry about at all.
The triode thd will have fallen below the noise floor and also be of zero
consequence.
So use the fet for its fine low noise properties in a phono/microphone input
stage
and use the tubes in regions where the fet cannot work without staining the
sound with crap.

bjts are a pain in the arse because of their low base-emitter input
resistance.
Fets are far better for discrete component audio stages where one wants
simplicity,
low noise, tube like distortions, and good music from phono.
When used as diff pairs, most of the fet distortion vanishes due to the 2H
cancelling
that occurs in a diff pair.

But why don't you just measure a fet, a triode, pentode
and bjt to find out about all this without me spoonfeeding you???

And many j-fets other than the highish gm ones I mention above have
little more gm than a signal pentode such as a 6AU6; 4mA/V is typical, and
these don't have the benefits of generating lots of gain which is usable in
a FB circuit, so thd remains high, so I never use things like an MPF102 or
such like.


Patrick Turner.




Patrick Turner wrote in
:

Modern transistors are more linear than even the best Triodes.

You have said this misleading statement before.

Unfortunately for your arguments this is not the case with regard to
voltage gain.
Transistors need only a small range of turn on voltage applied between
their base and emitter,
and their gm varies enormously between being on the threshold of turn
on of collector-emitter current and saturation.

Only enormous amounts of externally applied NFB corrects the inherent
voltage non-linearity
of all BJTs where there is substantial current change as in the case
of all power transistors.

Try setting up any bjt in common emitter mode without any emitter
resistor and apply
a voltage from a very low impedance to the base. The bjt is
disgustingly non linear
compared to a triode using no external applied NFB.
Even most pentodes which do not have internal electrostatic NFB like a
triode can easily
out perform a bjt.

I am not here to discuss whether the bjt amp can sound well, or
measure well. Both are known to be possible so it is believed by most
folks.

Without external loops of NFB including the emitter follower
connection which is a high amount of applied series voltage NFB, the
BJT is a hopeless voltage amp
unless we try to restrict the current change in the device, and then
the gain is

enormous and subject to the perils of the high collector resistance
and circuit slowness due to capacitances, and the non linear input
resistances of other
devices in the signal path.

A class A single bjt voltage amp stage with a single MJE340 with
another for a constant current source
collector load can have a gain of maybe 1,000, or like a pentode with
a CCS load in its anode circuit.
If external loops of shunt NFB are applied around either device, then
the linearity can be quite good for
either device, because for a gain reduction of 100, from 1,000 to 10,
the thd is also reduced about
100 fold.

The linearity is dependant on the NFB applied, and not on the basic
VOLTAGE linearity
of the device without NFB, which for a bjt is relatively poor, and
poorest when considerable
current change occurs in the device.

Patrick Turner.

[Andre Jute]

Patrick Turner wrote:

Andre Jute wrote:

You definitely have to keep perspective with NFB. I have no objection
to lesser designers using NFB in their amps to cover up their errors.
Solid state is a complete error, which accounts for why it is only
possible to implement with oodles of NFB. My best amp ever, the T113
EL34 triode-linked PP, in the original design had variable feedback but
hardly anyone bothered to build it in and now it isn't even on my own
T113.

Planned distortion cancellation is a chimera. Like NFB, it would not be
required if people would stop hogging tubes out to the ends of the
possible, impossible and totally impossible swing. A tube operated over
only a short part of its transfer curve is the most linear device known
to man.

Anything that requires NFB is by definition a bodge. You know the old
joke about the tailor fitting up an impressionable customer?

But one cannot avoid even unplanned distortion cancellations.

Who said anything about avoiding natural or native cancellations? We
welcome them, as we welcome the natural or native negative feedback
inherent in triodes. The negative feedback we hate is artificial,
added, loop, excessive, tasteless, thoughtlessly applied, deleterious,
wrecking.

In just about all SET amps the SET driving the output SET has 2H that cancels the 2H of the output tube,

Well, some of us aren't ashamed of liking what we like, and stuff a
417A or SRPP 6SL7 up the front of a 300B or an 845, or even PP EL34,
for a spot of glee intensification.

and with such tubes as the 845, the THD approaches 5% of mainly 2H at 25 watts and

Yes, but that's my point! If you need 25W you shouldn't be working with
SE845! Noise isn't linear; it is a non-linear ghost at the party,
starting as a cubic function (or worse) of power extracted. Three of
your five percentage points of HD arise from nowhere in the last 5W. It
would be far more sensible to use 845 only up to 19W or so, and beyond
that to parallel them or go to push-pull. And, in this regard, the 845
has a benevolent transfer function, all those grid lines
ruler-parallel, unlike some other tubes I can mention.

with about 110Vrms applied to its grid,

A sub-20W class A1 845 has operating points, off the top of my head,
with optimum 10K primary, of around 1kV plate, 80 milliamps of
quiescent current, bias a bit more than -150V, and signal pretty near
150V peak, current on the driver at least 20mA if the thing is not to
be frequency-limited below the capabilities of your trannies. That's a
tough drive requirement but 845 are for hard men who don't shy away
from hard work -- and they reward one accordingly. With these sort of
numbers I don't remember 5% distortion at all, more like well under
three-quarter per cent, but that's probably because we measured the
complete amp, after the choke-loaded 300B driver did its distortion
cancellation thing... g What I do remember is an experimental 845
with 95% of Pdmax, 90mA operating, giving nearly 38W in A2 with under
4.2%THD.

so with say an EL34 in triode as the driver
then this driver will produce about 3% 2H at 110Vrms which will cancel much of the 845 distortion
to reduce it to about 2%.

At a particular frequency, Patrick, surely? The problem with the
harmonic distortion cancellation schemes men propose is that the triode
gods didn't make any two of their children distort in perfect reverse
proportion across the frequency band.

Me, I'd rather run a shorter transfer curve, take fractionally less
power, and nail that silence down as my own property.

At 1 watt or less where such amps are to be used mostly, there is about 20Vrms needed at the 845 grid
and considerable 2H cancellation still occurs to reduce the thd to well under 1%
with the natural trickery offered by cascading triodes.
The 845 has such low Ra that the damping factor is fine with no loop NFB.
With an EL34 driver, the THD is also quite low enough and beautiful sound results,

845 is the true hedonist's amp. As a student I toured the States on the
Greyhound (99 buck ticket, go one way anywhere, make a big loop through
all the states). I listened to the smokey AM radio stations on a super
Sony radio I won gambling at a terminal. That formed a part of my
musical and aural taste. Years later I learned that many of those
stations still broadcast on war surplus 845.

and the low Ra results in wide bandwidth and low transformer distortions.
The 25 watt ceiling allows enough dynamic range and bob is your uncle, gertrude your aunt, sit back enjoy
and don't worry what might be done with silly con.
But one does have to make a nice power supply since there is no loop NFB to
ensure the noise is reduced by that method.

You also need a superior output transformer of the right impedance to
take maximum advantage of the intrinsic linearity of the 845, but I
imagine that's the least of your problems...

Patrick Turner.

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

[Andre Jute]

Trevor Wilson wrote:
"Andre Jute" wrote in message
oups.com...
Prune wrote:

"Andre Jute" wrote Our legislators managed to
criminalize fox-hunting and smoking; when
they will get off their collective fat arse and criminalize negative
feedback? It is clearly consumed only by undesirables.

LOL! Still, listening to stuff with limited amount of NFB in an amp that
has sufficient slew rate doesn't sound bad to my ears. But now there are
all sorts of alternatives like predistortion, using devices with inverse
nonlinearities, Hawksford error correction (feed back and/or forward the
error signal only instead of the whole signal), etc., so you can still get
low distortion without it.

I've dealt with slew rate as a separate matter in another thread.

You definitely have to keep perspective with NFB. I have no objection
to lesser designers using NFB in their amps to cover up their errors.
Solid state is a complete error, which accounts for why it is only
possible to implement with oodles of NFB. My best amp ever, the T113
EL34 triode-linked PP, in the original design had variable feedback but
hardly anyone bothered to build it in and now it isn't even on my own
T113.

Planned distortion cancellation is a chimera. Like NFB, it would not be
required if people would stop hogging tubes out to the ends of the
possible, impossible and totally impossible swing. A tube operated over
only a short part of its transfer curve is the most linear device known
to man.

Anything that requires NFB is by definition a bodge.

**What? like Triodes, with their massive amounts of internal NFB?

We've been here before, Trev-Baby, love of my life, kiss-kiss. NFB is
conventionally used to mean "added feedback" and even "added global
feedback". You know it. I know it. Everyone knows it. Your hysterical
arguments make sense only by ignoring a common convention of
engineering speech.

Triodes, with their massive amounts of internal NFB?

What, the 14dB or so inside a 300B, massive?

As usual, Jute, you are full of it. CORRECTLY applied, NFB can turn a crap
amp into a decent one. INCORRECTLY applied, it can turn a crap amp into a
more crappy one.

Be so much smarter in the first instance to design an amp that works
without the kludge.

BTW: Modern transistors are more linear than even the best Triodes.

After the application of a gazlllion dB of kludgeback, sure. And they
sound like it too.

--
Trevor Wilson
www.rageaudio.com.au

With lots of kisses and soothing cooing, Trev-Baby.

Andre Jute
"You can wait 'til more important things get taken care of."
-- Ned Carlson of TubeZone to a Customer who already waited *14 weeks*
for his tubes.

[Andre Jute]

Prune wrote:
"Andre Jute" wrote in
oups.com:

The good thing about Hawksford error correction is exactly that you are not
feeding back the signal but only the residual error. Indeed, EC can be
done as feedforward instead of feedback, in which case there's no recursion
whatsoever. EC essentially makes it possible to improve a given power
stage by using a very accurate low power stage. You can use it whether or
not there is NFB also present. And, though most discussion of it is in
applications to stages without significant gain (emitter/source/cathode
followers or heavily degenerated stages with little gain), it's
generalizable though more difficult to trim properly for stages that do
have significant gain.

I have a distinct suspicion of anyone who cannot explain his concepts
to me in plain English and Malcolm Hawsford is a decidedly suspicious
character. Nonetheless, I girded my loins and waded bravely into his
math back when even Martin Colloms, uniquely, admitted he didn't know
what it was all about. Having painfully crawled over Hawksford's field
of tintacks, I concluded that it was clever math and poor audio.

Hawksford's mechanism is exactly the same as the mechanism of NFB, to
chop the sound up into little bits and hope that the deleterious bits
will be under the perception threshhold. Nobody knows where the
perception threshhold is, but if what you (Prune) says about the
utility of THD measurements is correct (and it is, as I and others have
been saying for decades), the perception threshhold was always lower
than even Olson thought.

I concluded that, while NFB and Hawksford's variant are both
intellectually fascinating (if you get hold of a better class of
defendant than the clowns here, say for instance someone with brains
and an articulate goodwill to explain difficult concepts to the
innocent like Scott Frankland), for practical audio use they are the
same as going directly to digital.

I'll stick to tubes in simple ZNFB circuits, thanks.

Andre Jute
Simplicity is its own virtue

[Andre Jute]

I thought you'd show, Arny, like a maggot cut in half by the fish hook
still crawling towards the rotting carcass of negative feedback.

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

Arny Krueger wrote:
"Patrick Turner" wrote in message
...
Modern transistors are more linear than even the best Triodes.

You have said this misleading statement before.

Unfortunately for your arguments this is not the case with regard to
voltage
gain.
Transistors need only a small range of turn on voltage applied between
their
base and emitter,
and their gm varies enormously between being on the threshold of turn on
of
collector-emitter current and saturation.

It's almost like in Turner-world there are no such things as emitter
resistors.

Only enormous amounts of externally applied NFB corrects the inherent
voltage
non-linearity of all BJTs where there is substantial current change as in
the case of all
power transistors.

It's almost like in Turner-world there are no such things as emitter
followers.

Try setting up any bjt in common emitter mode without any emitter resistor
and
apply a voltage from a very low impedance to the base.

Proving once again that if you do something really stupid, you will get
suboptimal results.

I am not here to discuss whether the bjt amp can sound well, or measure
well.
Both are known to be possible so it is believed by most folks.

It's almost like in Turner-world sonic transparancy is the ultimate sin.

Without external loops of NFB including the emitter follower connection
which is a high amount of applied series voltage NFB, the BJT is a
hopeless
voltage amp unless we try to restrict the current change in the device,
and then the gain is
enormous and subject to the perils of the high collector resistance and
circuit slowness due to capacitances, and the non linear input resistances
of
other devices in the signal path.

Proving once again that if you do something really stupid, you will get
suboptimal results.

Yawn.

[Arny Krueger]

"Andre Jute" wrote in message
ps.com...

I thought you'd show, Arny, like a maggot cut in half by the fish hook
still crawling towards the rotting carcass of negative feedback.

Thanks Andre for demonstratting by example that you have nothing cogent to
say.

[Trevor Wilson]

"Prune" wrote in message
4.76...
"Trevor Wilson" wrote in
:
BTW: Modern transistors are more linear than even the best Triodes.

This is meaningless unless the specific distortion profile is weighted by
the nonlinear masking effects of the human ear and perceptual mechanism.

**********. Distortion profiles are dictated by topology, not the specific
device used. A more linear device will exhibit lower levels of distortion.

I've already pointed out references elsewhere that THD measurements do not
in general correlate with human perception of distortion in blind testing.

**Non-sequitur. The best transistors are more linear than the best Triodes.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

[Trevor Wilson]

"Patrick Turner" wrote in message
...
Modern transistors are more linear than even the best Triodes.

You have said this misleading statement before.

**It's not misleading. It's fact.


Unfortunately for your arguments this is not the case with regard to
voltage
gain.
Transistors need only a small range of turn on voltage applied between
their
base and emitter,
and their gm varies enormously between being on the threshold of turn on
of
collector-emitter current and saturation.

**Transistors are controlled by CURRENT, not Voltage. The CURRENT gain of
modern transistors is extremely linear, over a wide range of Collector
currents and Voltages.


Only enormous amounts of externally applied NFB corrects the inherent
voltage
non-linearity
of all BJTs where there is substantial current change as in the case of
all
power transistors.

**Transistors (BJTs) are CURRENT amplification devices.


Try setting up any bjt in common emitter mode without any emitter resistor
and
apply
a voltage from a very low impedance to the base. The bjt is disgustingly
non
linear
compared to a triode using no external applied NFB.

**Transistors (BJTs) are CURRENT amplification devices. Apply a current to
the Base and measure the change in Collector current. Get back to me when
you've done this.


Even most pentodes which do not have internal electrostatic NFB like a
triode
can easily
out perform a bjt.

**Not even close. Pentodes are vastly less linear than even average BJTs.
Triodes, at least, are reasonably linear.


I am not here to discuss whether the bjt amp can sound well, or measure
well.
Both are known to be possible so it is believed by most folks.

**Me either. I'm here to correct Jute's lies.


Without external loops of NFB including the emitter follower connection
which is a high amount of applied series voltage NFB, the BJT is a
hopeless
voltage amp


**Transistors (BJTs) are CURRENT amplification devices.

unless we try to restrict the current change in the device, and then the
gain is

enormous and subject to the perils of the high collector resistance and
circuit slowness due to capacitances, and the non linear input resistances
of
other
devices in the signal path.

A class A single bjt voltage amp stage with a single MJE340 with another
for a
constant current source
collector load can have a gain of maybe 1,000, or like a pentode with a
CCS load
in its anode circuit.
If external loops of shunt NFB are applied around either device, then the
linearity can be quite good for
either device, because for a gain reduction of 100, from 1,000 to 10, the
thd is
also reduced about
100 fold.

The linearity is dependant on the NFB applied, and not on the basic
VOLTAGE
linearity
of the device without NFB, which for a bjt is relatively poor, and poorest
when
considerable
current change occurs in the device.

**Transistors (BJTs) are CURRENT amplification devices.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

[Trevor Wilson]

"Andre Jute" wrote in message
oups.com...

Trevor Wilson wrote:
"Andre Jute" wrote in message
oups.com...
Prune wrote:

"Andre Jute" wrote Our legislators managed to
criminalize fox-hunting and smoking; when
they will get off their collective fat arse and criminalize negative
feedback? It is clearly consumed only by undesirables.

LOL! Still, listening to stuff with limited amount of NFB in an amp
that
has sufficient slew rate doesn't sound bad to my ears. But now there
are
all sorts of alternatives like predistortion, using devices with
inverse
nonlinearities, Hawksford error correction (feed back and/or forward
the
error signal only instead of the whole signal), etc., so you can still
get
low distortion without it.

I've dealt with slew rate as a separate matter in another thread.

You definitely have to keep perspective with NFB. I have no objection
to lesser designers using NFB in their amps to cover up their errors.
Solid state is a complete error, which accounts for why it is only
possible to implement with oodles of NFB. My best amp ever, the T113
EL34 triode-linked PP, in the original design had variable feedback but
hardly anyone bothered to build it in and now it isn't even on my own
T113.

Planned distortion cancellation is a chimera. Like NFB, it would not be
required if people would stop hogging tubes out to the ends of the
possible, impossible and totally impossible swing. A tube operated over
only a short part of its transfer curve is the most linear device known
to man.

Anything that requires NFB is by definition a bodge.

**What? like Triodes, with their massive amounts of internal NFB?

We've been here before, Trev-Baby, love of my life, kiss-kiss. NFB is
conventionally used to mean "added feedback" and even "added global
feedback". You know it. I know it. Everyone knows it. Your hysterical
arguments make sense only by ignoring a common convention of
engineering speech.

**NFB is NFB, regardless of how it is applied. You can ignore the facts as
much as you wish.


Triodes, with their massive amounts of internal NFB?

What, the 14dB or so inside a 300B, massive?

**Significantly more than a Pentode. Massive seems to be the appropriate
term to use.


As usual, Jute, you are full of it. CORRECTLY applied, NFB can turn a
crap
amp into a decent one. INCORRECTLY applied, it can turn a crap amp into a
more crappy one.

Be so much smarter in the first instance to design an amp that works
without the kludge.

**Read my lips: ALL AMPLIFIERS USE NFB. EVERY SINGLE ONE.


BTW: Modern transistors are more linear than even the best Triodes.

After the application of a gazlllion dB of kludgeback, sure. And they
sound like it too.

**Nope. Modern BJTs are more linear than Triodes. With or without feedback.
I understand that your experiences with BJTs ceased with the advent of the
2N3055, back in the 1960s, but you need to know that transistor technology
has moved on considerably since that time. Modern (power) transistors are
exceptionally linear devices. Far more linear than the best Triodes.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

[Eeyore]

Patrick Turner wrote:

Modern transistors are more linear than even the best Triodes.

You have said this misleading statement before.

Unfortunately for your arguments this is not the case with regard to voltage
gain.Transistors need only a small range of turn on voltage applied between their
base and emitter, and their gm varies enormously between being on the threshold of
turn on of
collector-emitter current and saturation.

You're being intentionally disingenous.

Jootikins already stated that toobs need to be operated with a restricted change in
Ia to be acceptable linear too.

If you take a single transistor amplifier circuit and do the same, let's say at ~
1mA Then for a typical small-signal silicon device the gm will be 40mA/V ( basic
physics ). Much greater than any toob, note !

If you restrict the signal level to say +-10% of Iq then the change in gm will be
from ~ 36 to 44 mA/V ( also +- 10% ) . Not exactly an *enormous change* !

Of course, you're also assuming that transistors should be operated in exactly the
same circuit configuration as toobs in order to get the worst results to be able to
blame them !

A 12AX7 for example has a gm of about 2mA/V at the same Iq - so to get the same gain
from a transistor stage we need to apply local feedback of 20x ( emitter
degeneration ) to make it truly equivalent.

This local feedback will linearise the +-10% swing in gm down to +-0.5% i.e from
40mA/V +-10% to 2mA/V +-0.5% ( 1.99 - 2.01 mA/V ).

Now tell me the change in gm for a 12AX7 over the same range !

And that's just for a single transistor. If one abandones the artificial 'thought
experiment' of restricting the direct comparison of one device to another and takes
advantage of the transistor's vastly lower cost, the obviuos choice for a gain stage
using transistors is the compound arrangement using an npn and a pnp. I this case,
the first device is operating at a near constant Ic and therefore the change in gm
is utterly miniscule !

Along with many others, I use such a configuration in a long-tailed pair arrangement
for mic input circuits and at the lower gains, say up to ~ 30dB or 30x ( much more
than any toob stage ) the distortion is barely measurable even using AP test gear.
Well below 0.01% for example - ISTR ~ 0.005% actually and it's barely just
measurable out of the noise floor - with *no* overall feedback !

It's damn quiet too ! Something a toob can never be.

Graham

[Eeyore]

Andre Jute wrote:

I have a distinct suspicion of anyone who cannot explain his concepts
to me in plain English

Because you can't understand science quite clearly.

You're a buffoon and charlatan, Jute !

Graham

[Arny Krueger]

"flipper" wrote in message
...
On Tue, 25 Jul 2006 09:16:18 -0400, "Arny Krueger"
wrote:


"Patrick Turner" wrote in message
...

Modern transistors are more linear than even the best Triodes.

You have said this misleading statement before.

Unfortunately for your arguments this is not the case with regard to
voltage
gain.
Transistors need only a small range of turn on voltage applied between
their
base and emitter,
and their gm varies enormously between being on the threshold of turn on
of
collector-emitter current and saturation.

It's almost like in Turner-world there are no such things as emitter
resistors.

Only enormous amounts of externally applied NFB corrects the inherent
voltage
non-linearity of all BJTs where there is substantial current change as
in
the case of all
power transistors.

It's almost like in Turner-world there are no such things as emitter
followers.

No, the problem is you make a claim about "modern transistors" and
then switch to arguing about circuit topology.

You're mistaken, and owe me an apology. The line about "modern transistors"
came from Trevor, not me.

[Eeyore]

Arny Krueger wrote:

"flipper" wrote in message
...

No, the problem is you make a claim about "modern transistors" and
then switch to arguing about circuit topology.

You're mistaken, and owe me an apology. The line about "modern transistors"
came from Trevor, not me.

I' saying nuttin about 'modern transistors' in that respect other than to
comment that 300V small-signal transistors are these days ( and for ~ the last
25 years actually ) readily available and at low cost too. It would be almost
trivially simple to make some transistors fit in a 9 bin base and compare almost
directly ( some bias voltage issues ).

Topology is the biggie though. Transistors are hugely more versatile in this
respect.

Graham

[Trevor Wilson]

"Patrick Turner" wrote in message
...


Trevor Wilson wrote:

"Prune" wrote in message
4.76...
"Trevor Wilson" wrote in
:
BTW: Modern transistors are more linear than even the best Triodes.

This is meaningless unless the specific distortion profile is weighted
by
the nonlinear masking effects of the human ear and perceptual
mechanism.

**********. Distortion profiles are dictated by topology, not the
specific
device used. A more linear device will exhibit lower levels of
distortion.

I've already pointed out references elsewhere that THD measurements do
not
in general correlate with human perception of distortion in blind
testing.

**Non-sequitur. The best transistors are more linear than the best
Triodes.

Please propose a test to compare the two.

**For the BJT:

A suitable supply Voltage for Collector and Emitter. Apply a current to the
Base. Vary that current from (say) 1mA to (say) 10 Amps. Graph the result.

For the Triode (or more amusingly) the Pentode:

A suitable supply Voltage for Plate and Cathode. Apply a Voltage to the
Grid. Vary that Voltage from (say) 0 Volts to (say) -50 Volts (or whatever
the limits of the tube are. Graph the result.

A modern power transistor will display a more linear amplification curve
than any tube. And over a much broader range.

I will readily acknowledge that transistors which Jute continually refer to
(2N3055, et al) are not particularly linear devices. Since his experience
appears to be limited to these, quite primitive, devices, it is hardly
surprising that he feels that a tube: "...is the most linear device known to
man." If he ever managed to pull his head out from his own arse, he would
realise that transistor technology has advanced significantly in the last 40
years.



--
Trevor Wilson
www.rageaudio.com.au




--
Posted via a free Usenet account from http://www.teranews.com

[Patrick Turner]

Andre Jute wrote:

Patrick Turner wrote:

Andre Jute wrote:

You definitely have to keep perspective with NFB. I have no objection
to lesser designers using NFB in their amps to cover up their errors.
Solid state is a complete error, which accounts for why it is only
possible to implement with oodles of NFB. My best amp ever, the T113
EL34 triode-linked PP, in the original design had variable feedback but
hardly anyone bothered to build it in and now it isn't even on my own
T113.

Planned distortion cancellation is a chimera. Like NFB, it would not be
required if people would stop hogging tubes out to the ends of the
possible, impossible and totally impossible swing. A tube operated over
only a short part of its transfer curve is the most linear device known
to man.

Anything that requires NFB is by definition a bodge. You know the old
joke about the tailor fitting up an impressionable customer?

But one cannot avoid even unplanned distortion cancellations.

Who said anything about avoiding natural or native cancellations? We
welcome them, as we welcome the natural or native negative feedback
inherent in triodes.

But I have seen attempts to load driver stages to cause extra even order distortions to
enhance the cancellation effects 2H between a driver and an output tube.
This isn't optimal imho because with all cascaded stages you get distortion of the distortions
so to speak and a fine mist of crap accumulates.

The negative feedback we hate is artificial,

added, loop, excessive, tasteless, thoughtlessly applied, deleterious,
wrecking.

Depends on the circumstances. I myself would think that pentodes and tetrodes need some loop FB
to bring them into the fold of the fidelity we wish them to be in.
bjts and mosfets et all like pentodes and tetrodes don't have internal electrostatic FB
so external loops are the only way.



In just about all SET amps the SET driving the output SET has 2H that cancels the 2H of the output tube,

Well, some of us aren't ashamed of liking what we like, and stuff a
417A or SRPP 6SL7 up the front of a 300B or an 845, or even PP EL34,
for a spot of glee intensification.

Indeed, and the music flows. Its all about thresholds.
One SE amp I tested and listened to had a lone EL34 in pentode driven by a 12AX7
with sub optimal loading; 2.5k with Ea = 450V, made in Thailand where the heat makes them
impevious to the message of the RDH4. There was a massive 1% thd at a watt and
it sounded dreadful above a wisper; the owner said it was no better than the generic transistor horror
he'd been using.



and with such tubes as the 845, the THD approaches 5% of mainly 2H at 25 watts and

Yes, but that's my point! If you need 25W you shouldn't be working with
SE845! Noise isn't linear; it is a non-linear ghost at the party,
starting as a cubic function (or worse) of power extracted. Three of
your five percentage points of HD arise from nowhere in the last 5W. It
would be far more sensible to use 845 only up to 19W or so, and beyond
that to parallel them or go to push-pull. And, in this regard, the 845
has a benevolent transfer function, all those grid lines
ruler-parallel, unlike some other tubes I can mention.

That's why I went on to mention that such amps are mostly used at a watt average max.

The thd is nearly proportional to output voltage in most amps.
so a 25 watt amp at 2.5 watts has 1/ 3.2 times the output voltage and thd
is thus 1/3.2 of the amount at clipping onset, or slightly less,
sometimes its 1/4 of the clipping level, but the other thing about listening level thd is that
its comprised of less harmonic numbers, and the resulting IMD products which are really
the worry are less sonically horrible, being low in level and complexity.



with about 110Vrms applied to its grid,

A sub-20W class A1 845 has operating points, off the top of my head,
with optimum 10K primary, of around 1kV plate, 80 milliamps of
quiescent current, bias a bit more than -150V, and signal pretty near
150V peak, current on the driver at least 20mA if the thing is not to
be frequency-limited below the capabilities of your trannies.

That's all about right.
I'm trying a 1:1 IST from an EL34 in SET to drive a pair of parallel 845.
The gain is low, so the Miller C is low, and Ia in the '34 is planned to be 30mA max,
to lift the working point of the '34 up from the curved lower Ra lines.


That's a
tough drive requirement but 845 are for hard men who don't shy away
from hard work -- and they reward one accordingly. With these sort of
numbers I don't remember 5% distortion at all, more like well under
three-quarter per cent, but that's probably because we measured the
complete amp, after the choke-loaded 300B driver did its distortion
cancellation thing... g What I do remember is an experimental 845
with 95% of Pdmax, 90mA operating, giving nearly 38W in A2 with under
4.2%THD.

I'm using KR Audio 845 at Ea = 1,100V, Ia = 75mA, RL = 6k for the two tubes.
About 48 watts is all one can get in class A1, with about 120Vrms of drive to the grid and 536Vrms at the
anodes.


so with say an EL34 in triode as the driver

then this driver will produce about 3% 2H at 110Vrms which will cancel much of the 845 distortion
to reduce it to about 2%.

At a particular frequency, Patrick, surely?

The phase relationship of drive voltage and output anode voltage and the 2H harmonics
is remarkably linear between 50Hz and 20kHz because the Ra of the driver triode and output triode
have such low values.


The problem with the
harmonic distortion cancellation schemes men propose is that the triode
gods didn't make any two of their children distort in perfect reverse
proportion across the frequency band.

In my SE35 CFB amps the output stage with a quad of 6CA7 with 12.5% of CFB from the OPT
produces about 2% thd, mainly 2H, at rated power into 5 ohms.
This is neatly cancelled by the EL84 driver tube producing the 46Vrms of required drive
and what you get is almost no 2H at all levels because the rates of increase of 2H
in driver and output are the same up to clipping, and the THD is as low as a good PP amp and consisting
of the same sorts of odd order harmonics as the PP amp.
There is slightly more to this story that this simple realisation of thd cancellations, because the
2H in pentodes and tetrodes varies enormously with load, and its phase changes relative to loads,
even if they are purely resistive. Read my website to know more.

But with triodes or SEUL the THD is usually more than a CFB stage with beam/pents.
Remember the NFB in a triode is delivered by non linear electrostatic routes based on a rule with the
applied voltages proportional to the cube root of something squared.
The amount of 2H cancellation with a 6V6 in triode that I use to drive a 13E1 in SEUL is minimal,
but useful and thd was 6dB less than when i had a more linear paralleled ECC32 but methinks the
6V6 makes better music.......
At normal levels the thd is all less than 0.2%, and mainly only 2H, so all is well.


Me, I'd rather run a shorter transfer curve, take fractionally less
power, and nail that silence down as my own property.

At 1 watt or less where such amps are to be used mostly, there is about 20Vrms needed at the 845 grid
and considerable 2H cancellation still occurs to reduce the thd to well under 1%
with the natural trickery offered by cascading triodes.
The 845 has such low Ra that the damping factor is fine with no loop NFB.
With an EL34 driver, the THD is also quite low enough and beautiful sound results,

845 is the true hedonist's amp. As a student I toured the States on the
Greyhound (99 buck ticket, go one way anywhere, make a big loop through
all the states). I listened to the smokey AM radio stations on a super
Sony radio I won gambling at a terminal. That formed a part of my
musical and aural taste. Years later I learned that many of those
stations still broadcast on war surplus 845.

Indeed, but the 845 were probably running in near class B in PP.
I recall the station engineers routinely checked that thd was less than 2%
during the audio tests on many stations.
The audio was detected, compared to the signal going to the modulator,
and the modulation was linearized with NFB....

I doubt if many radio stations used the 845 in class A, and in SE, this is the
real hedonistic use of tubes, like having a party with 40 tarts and ten gallons of plonk
rather than with a wife and only one bottle.



and the low Ra results in wide bandwidth and low transformer distortions.
The 25 watt ceiling allows enough dynamic range and bob is your uncle, gertrude your aunt, sit back enjoy
and don't worry what might be done with silly con.
But one does have to make a nice power supply since there is no loop NFB to
ensure the noise is reduced by that method.

You also need a superior output transformer of the right impedance to
take maximum advantage of the intrinsic linearity of the 845, but I
imagine that's the least of your problems...

It took some time before I concluded the OPT design, with 3,000 P turns on a GOSS
gapped E&I core of 70mm stack x 50 tongue.

But I will be trying a floating 1,100V supply connected between one end of the P to the
845 anodes. The other end of the P is grounded, so that the supply
is like a large floating battery and the OPT primary is at ground potential and thus not exposed to the
pressure of the 1,100V supply.
The only thing special I have to do is add an electrostaic foil screen on the power tranny to allow
the whole B+ supply to float without noise from a mains winding getting into the
anode signal via the stray C. Capacitance to 0V is slightly more, but with Ra of the pair
of 845 at about 1k the C won't drag the response down.
211 could also be used in the same amp.

I thought of doing the driver amp the same way but with Ea = 350V its not necessary.
The IST will be 1:1, with its Lp 50H, and thus the anode can be cap coupled to the secondary
for direct transfer of HF drive rather than suffer the horrors of the leakage inductance
of the IST causing reactive troubles at the higher audio F.
The secondary of the IST has a low winding resistance which keeps the output grids at the applied
-120V bias. The total bias will be about -160V, with 40V generated with cathode biasing of each 845 with
a 75mA CCS using transistors.
The two cathodes of each 845 will be seperately bypassed to 0V with 1,000 uF.
DC will be applied to the cathodes for heating.
Active protection against cathode voltage rise will be employed in case a tube takes off.

The heater supplies have to make 10V at 3.3 amps for each 845 if chinese 845 are to be used.
The KR Audio have KR's unique cathode technology needing only 10V at 1A.
It appears the KR cathodes are oxide coated types rather than tungsten and it remains to be
seen how many years these last, because oxide coated cathodes suffer from bombardment
more when there is an anode voltage of 1,000V than when it is a mild 400V in most normal tubes.
The higher voltage gives the positively charged gas molecules are higher velocity as they
travel to the cathode.
The KR cathodes allow far less heat to be radiated from the cathode so the Pda
rating of the tube can be higher.

I like the KR300B which will happily run with Pda = 40 watts for 10 watts of lazy triode power.
A pair should be capable of 40 watts of PP AB1 power with only 60W of idle power for the two.

Patrick Turner.

[Patrick Turner]

Arny Krueger wrote:

"Patrick Turner" wrote in message
...
Modern transistors are more linear than even the best Triodes.

You have said this misleading statement before.

Unfortunately for your arguments this is not the case with regard to
voltage
gain.
Transistors need only a small range of turn on voltage applied between
their
base and emitter,
and their gm varies enormously between being on the threshold of turn on
of
collector-emitter current and saturation.

It's almost like in Turner-world there are no such things as emitter
resistors.

I am forced to used Re to linearize bjts....



Only enormous amounts of externally applied NFB corrects the inherent
voltage
non-linearity of all BJTs where there is substantial current change as in
the case of all
power transistors.

It's almost like in Turner-world there are no such things as emitter
followers.

This is a huge amount of series voltage NFB....



Try setting up any bjt in common emitter mode without any emitter resistor
and
apply a voltage from a very low impedance to the base.

Proving once again that if you do something really stupid, you will get
suboptimal results.

I am not here to discuss whether the bjt amp can sound well, or measure
well.
Both are known to be possible so it is believed by most folks.

It's almost like in Turner-world sonic transparancy is the ultimate sin.

I get all the transparancy I want.

Why does Arny suggest that i sin with ultimate badness?

I think I just got KROOGERED!





Without external loops of NFB including the emitter follower connection
which is a high amount of applied series voltage NFB, the BJT is a
hopeless
voltage amp unless we try to restrict the current change in the device,
and then the gain is
enormous and subject to the perils of the high collector resistance and
circuit slowness due to capacitances, and the non linear input resistances
of
other devices in the signal path.

Proving once again that if you do something really stupid, you will get
suboptimal results.

......Another statement of BS, dislocated from the preceding text....

Patrick Turner.

Yawn.

[Patrick Turner]

Trevor Wilson wrote:

"Prune" wrote in message
4.76...
"Trevor Wilson" wrote in
:
BTW: Modern transistors are more linear than even the best Triodes.

This is meaningless unless the specific distortion profile is weighted by
the nonlinear masking effects of the human ear and perceptual mechanism.

**********. Distortion profiles are dictated by topology, not the specific
device used. A more linear device will exhibit lower levels of distortion.

I've already pointed out references elsewhere that THD measurements do not
in general correlate with human perception of distortion in blind testing.

**Non-sequitur. The best transistors are more linear than the best Triodes.

Please propose a test to compare the two.

Patrick Turner.



--
Trevor Wilson
www.rageaudio.com.au

--
Posted via a free Usenet account from http://www.teranews.com

[Patrick Turner]

Trevor Wilson wrote:

"Patrick Turner" wrote in message
...
Modern transistors are more linear than even the best Triodes.

You have said this misleading statement before.

**It's not misleading. It's fact.

Nothing is a fact until all sides agree it is, and you have to proove what you
say.





Unfortunately for your arguments this is not the case with regard to
voltage
gain.
Transistors need only a small range of turn on voltage applied between
their
base and emitter,
and their gm varies enormously between being on the threshold of turn on
of
collector-emitter current and saturation.

**Transistors are controlled by CURRENT, not Voltage. The CURRENT gain of
modern transistors is extremely linear, over a wide range of Collector
currents and Voltages.

Current relationships between base and collector currents are substantially
linear.
The voltage relationship is not.
You don't have the concepts correctly in your mind.




Only enormous amounts of externally applied NFB corrects the inherent
voltage
non-linearity
of all BJTs where there is substantial current change as in the case of
all
power transistors.

**Transistors (BJTs) are CURRENT amplification devices.

Sure, we all know that, but their voltage linearity is intrinsically poor.





Try setting up any bjt in common emitter mode without any emitter resistor
and
apply
a voltage from a very low impedance to the base. The bjt is disgustingly
non
linear
compared to a triode using no external applied NFB.

**Transistors (BJTs) are CURRENT amplification devices. Apply a current to
the Base and measure the change in Collector current. Get back to me when
you've done this.

The current applied to the base is propelled by the applied voltage.
No voltage = no current.

Set up a small bjt in bread board as a an SE device in class A with zero NFB and
record the
voltage linearity. Its terrible.
Lots of NFB is needed to linearize the bjt, which is easy, because they have a
lot of gain...


Even most pentodes which do not have internal electrostatic NFB like a
triode
can easily
out perform a bjt.

**Not even close. Pentodes are vastly less linear than even average BJTs.
Triodes, at least, are reasonably linear.

Your ignorance of tube behaviour is breathtaking.

Try reading RDH4 about the comparison of triode connected pentodes
and the same tube running as a pentode.
At low levels the pentode was more linear than the triode.




I am not here to discuss whether the bjt amp can sound well, or measure
well.
Both are known to be possible so it is believed by most folks.

**Me either. I'm here to correct Jute's lies.


Without external loops of NFB including the emitter follower connection
which is a high amount of applied series voltage NFB, the BJT is a
hopeless
voltage amp

**Transistors (BJTs) are CURRENT amplification devices.

No need to emulate a trained galah.



unless we try to restrict the current change in the device, and then the
gain is

enormous and subject to the perils of the high collector resistance and
circuit slowness due to capacitances, and the non linear input resistances
of
other
devices in the signal path.

A class A single bjt voltage amp stage with a single MJE340 with another
for a
constant current source
collector load can have a gain of maybe 1,000, or like a pentode with a
CCS load
in its anode circuit.
If external loops of shunt NFB are applied around either device, then the
linearity can be quite good for
either device, because for a gain reduction of 100, from 1,000 to 10, the
thd is
also reduced about
100 fold.

The linearity is dependant on the NFB applied, and not on the basic
VOLTAGE
linearity
of the device without NFB, which for a bjt is relatively poor, and poorest
when
considerable
current change occurs in the device.

**Transistors (BJTs) are CURRENT amplification devices.

Gee, I think I heard that parrot again.

Maybe you could confirm what i am saying if you
went right back to basics with a breadboard and a CRO
and examined the basic workings of the basic devices that mankind has
invented over the last 100 years.

Patrick Turner.



--
Trevor Wilson
www.rageaudio.com.au

--
Posted via a free Usenet account from http://www.teranews.com

[Patrick Turner]

**Nope. Modern BJTs are more linear than Triodes. With or without feedback.
I understand that your experiences with BJTs ceased with the advent of the
2N3055, back in the 1960s, but you need to know that transistor technology
has moved on considerably since that time. Modern (power) transistors are
exceptionally linear devices. Far more linear than the best Triodes.

Unfortunately, our Trevor fails to understand the very basics about transistors,
and confuses their
input/output current linearity with their voltage linearity which is poor, hence

large amounts of series voltage negative FB and series current negative FB must
be employed.

if what Trevor was saying was true, then you wouldn't need to use any NFB loops
with transistors, but one must use FB with transistors, since without NFB they
cannot be used at all.

Trevor tries to correct Jute's assertions about the perils of NFB but tells
bigger lies
to posture in a worse position.

Its not until one designs, builds and then listens to ones creations that
understanding the need for
NFB or not begins to be apparent, depending on the devices and the operating
conditions.
Using NFB cannot be explained in one sentence.



Patrick Turner.

[Eeyore]

Andre Jute wrote:

Trevor Wilson wrote:

BTW: Modern transistors are more linear than even the best Triodes.

After the application of a gazlllion dB of kludgeback, sure. And they
sound like it too.

Your absurd obsession with feedback sounding bad is a very tired and entirely
wrong premise based on former poor practice rarely seen any more.

In my example elsewhere in this thread I used 26dB of local feedback ( hardly
gazillions ) to make a transistor's gm equivalent to a 12AX7 for instance. I'll
venture that the transistor circuit is more linear too !

Without doing that, transistors would have vastly more stage gain than any toob,
rendering any meaningful comparison impossible.

Graham

[Eeyore]

Patrick Turner wrote:

Trevor tries to correct Jute's assertions about the perils of NFB but tells
bigger lies to posture in a worse position.

There is no peril whatever with NFB when intelligently and correctly applied.

Graham

[Patrick Turner]

Eeyore wrote:

Patrick Turner wrote:

Modern transistors are more linear than even the best Triodes.

You have said this misleading statement before.

Unfortunately for your arguments this is not the case with regard to voltage
gain.Transistors need only a small range of turn on voltage applied between their
base and emitter, and their gm varies enormously between being on the threshold of
turn on of
collector-emitter current and saturation.

You're being intentionally disingenous.

Jootikins already stated that toobs need to be operated with a restricted change in
Ia to be acceptable linear too.

If you take a single transistor amplifier circuit and do the same, let's say at ~
1mA Then for a typical small-signal silicon device the gm will be 40mA/V ( basic
physics ). Much greater than any toob, note !

If you restrict the signal level to say +-10% of Iq then the change in gm will be
from ~ 36 to 44 mA/V ( also +- 10% ) . Not exactly an *enormous change* !

But if the R load of the bjt was say 5k6 in a typical circuit with a 12V rail supply,
then 10% Ic change gives +/- 0.1mA, or 0.39vrms of output.
If the change in gm is 36 to 44, then the gain change over a swing of 0.39Vrms is 5%,
and I dare not calculate the 2H but it will be large.

The use of a triode with 56k load and with a +/-10% in Ia won't result in anything like
the
huge gm change you have in your bjt and the thd will be far less, even at 10 times the
output voltage.



Of course, you're also assuming that transistors should be operated in exactly the
same circuit configuration as toobs in order to get the worst results to be able to
blame them !

A 12AX7 for example has a gm of about 2mA/V at the same Iq - so to get the same gain
from a transistor stage we need to apply local feedback of 20x ( emitter
degeneration ) to make it truly equivalent.

This local feedback will linearise the +-10% swing in gm down to +-0.5% i.e from
40mA/V +-10% to 2mA/V +-0.5% ( 1.99 - 2.01 mA/V ).

Now tell me the change in gm for a 12AX7 over the same range !

And that's just for a single transistor. If one abandones the artificial 'thought
experiment' of restricting the direct comparison of one device to another and takes
advantage of the transistor's vastly lower cost, the obviuos choice for a gain stage
using transistors is the compound arrangement using an npn and a pnp. I this case,
the first device is operating at a near constant Ic and therefore the change in gm
is utterly miniscule !

Along with many others, I use such a configuration in a long-tailed pair arrangement
for mic input circuits and at the lower gains, say up to ~ 30dB or 30x ( much more
than any toob stage ) the distortion is barely measurable even using AP test gear.
Well below 0.01% for example - ISTR ~ 0.005% actually and it's barely just
measurable out of the noise floor - with *no* overall feedback !

It's damn quiet too ! Something a toob can never be.

Usually the studio background noise is higher than the tube noise if they are used
in a critical situation.

Many samples od consumer electronics, amps and receivers were noisier than tubes gear
done well.
Anyway, noise isn't a problem in anything I build now.

Nor is the distortion.

All I am saying is that where one wants to make 20V for driving speakers,
transistors will need as much NFB as can be used unless the circuit is in class A like
nearly all tube amps
which usually provide enough class A power for all the of the music levels.
Typical 50 watt 2 x KT88 power amp in cfb or ul makes about 0.03% at 1 watt.
I know of none who can discern whether such distortion exists or not in any amplifier.
Such typical tube amp performance is doable with only a max of 20 dB of global NFB
But a bjt amp seems to need 60 dB unless its a class A type, and then 20 dB is usually
enough.

I am over simplifying, but desoite your arguments I still believe there is not a single
SS
device that is more linear than a 6SN7 with a constant current load for 20Vrms of
output,
and not a single external loop of NFB including emitter folls, shunt FB, emitter R etc.
And the 6SN7 in a diff pair will have even lower thd where there is extremely low 3H
and virtually no 2H and again, with no loop FB.

Perhaps you should try to convince the guys at rec.timber.boats to start using
fibreglass
or steel to build their craft.

But this is a tubecraft site, and those of us who like tubes see little reason to give
them away.

And I have built quite a few SS amps, and I know about pairs of NPN and PNP drivers et
all, see my web pages.

Patrick Turner.



Graham

[Patrick Turner]

Eeyore wrote:

Patrick Turner wrote:

Trevor tries to correct Jute's assertions about the perils of NFB but tells
bigger lies to posture in a worse position.

There is no peril whatever with NFB when intelligently and correctly applied.

Graham

I happen to agree with you here. I use NFB as I see fit.

But Trevor tried to say there would be little reason why one couldn't build
a bjt amp without NFB.

Since he said bjts are so darn linear, then why not dispense entirely with
the NFB?

Patrick Turner.

[Tom Schlangen]

Hi Trevor,

BTW: Modern transistors are more linear
than even the best Triodes.

I don't know much about recent transistors, so this
is new to me and sounds interesting.

Does it hold true for, for example, comparable circuits,
like building a SE triode or SE transistor amp, both w/o
gNFB?

Tom

--
When in doubt, use brute force.
- Ken Thompson

[Arny Krueger]

"flipper" wrote in message
news
On Tue, 25 Jul 2006 18:41:37 -0400, "Arny Krueger"
wrote:


"flipper" wrote in message
. ..
On Tue, 25 Jul 2006 09:16:18 -0400, "Arny Krueger"
wrote:


"Patrick Turner" wrote in message
...

Modern transistors are more linear than even the best Triodes.

You have said this misleading statement before.

Unfortunately for your arguments this is not the case with regard to
voltage
gain.
Transistors need only a small range of turn on voltage applied between
their
base and emitter,
and their gm varies enormously between being on the threshold of turn
on
of
collector-emitter current and saturation.

It's almost like in Turner-world there are no such things as emitter
resistors.

Only enormous amounts of externally applied NFB corrects the inherent
voltage
non-linearity of all BJTs where there is substantial current change
as
in
the case of all
power transistors.

It's almost like in Turner-world there are no such things as emitter
followers.

No, the problem is you make a claim about "modern transistors" and
then switch to arguing about circuit topology.

You're mistaken, and owe me an apology. The line about "modern
transistors"
came from Trevor, not me.

Then change it to...

Too bad about that character problem you've got, Mr. alias.

No, the problem is you take the clearly stated
topic "modern transistors" and switch to arguing about circuit
topology.

When you show me a transistor or a tube amplifying audio without a
supporting circuit topology, then and only then will you have made your
point.

The problem is that Patrick obviously intentionally picked a well-known
high-distortion circuit topology to make his point.

[Arny Krueger]

"Patrick Turner" wrote in message
...


Arny Krueger wrote:

"Patrick Turner" wrote in message
...
Modern transistors are more linear than even the best Triodes.

You have said this misleading statement before.

Unfortunately for your arguments this is not the case with regard to
voltage
gain.
Transistors need only a small range of turn on voltage applied between
their
base and emitter,
and their gm varies enormously between being on the threshold of turn
on
of
collector-emitter current and saturation.

It's almost like in Turner-world there are no such things as emitter
resistors.

I am forced to used Re to linearize bjts....

So what? Re also helps with bias stability.

Only enormous amounts of externally applied NFB corrects the inherent
voltage
non-linearity of all BJTs where there is substantial current change as
in
the case of all
power transistors.

It's almost like in Turner-world there are no such things as emitter
followers.

This is a huge amount of series voltage NFB....

If NFB is such a sonic terror, why did almost every tubed audio amp and
preamp of the days of tubes have it?

Try setting up any bjt in common emitter mode without any emitter
resistor
and
apply a voltage from a very low impedance to the base.

Proving once again that if you do something really stupid, you will get
suboptimal results.

I am not here to discuss whether the bjt amp can sound well, or measure
well.
Both are known to be possible so it is believed by most folks.

It's almost like in Turner-world sonic transparancy is the ultimate sin.

I get all the transparancy I want.

So do I. Only, I'm obviously harder to please than you are, Pat.

Why does Arny suggest that i sin with ultimate badness?

I think I just got KROOGERED!

Figure of speech.

Without external loops of NFB including the emitter follower connection
which is a high amount of applied series voltage NFB, the BJT is a
hopeless
voltage amp unless we try to restrict the current change in the device,
and then the gain is
enormous and subject to the perils of the high collector resistance
and
circuit slowness due to capacitances, and the non linear input
resistances
of
other devices in the signal path.

Proving once again that if you do something really stupid, you will get
suboptimal results.

.....Another statement of BS, dislocated from the preceding text....

Not BS, just accepted practice, even in the heyday of tubes, back in the
60s.

[Arny Krueger]

"flipper" wrote in message
...
On Wed, 26 Jul 2006 07:49:27 -0400, "Arny Krueger"
wrote:


"flipper" wrote in message
news
On Tue, 25 Jul 2006 18:41:37 -0400, "Arny Krueger"
wrote:


"flipper" wrote in message
m...
On Tue, 25 Jul 2006 09:16:18 -0400, "Arny Krueger"
wrote:


"Patrick Turner" wrote in message
. ..

Modern transistors are more linear than even the best Triodes.

You have said this misleading statement before.

Unfortunately for your arguments this is not the case with regard to
voltage
gain.
Transistors need only a small range of turn on voltage applied
between
their
base and emitter,
and their gm varies enormously between being on the threshold of
turn
on
of
collector-emitter current and saturation.

It's almost like in Turner-world there are no such things as emitter
resistors.

Only enormous amounts of externally applied NFB corrects the
inherent
voltage
non-linearity of all BJTs where there is substantial current change
as
in
the case of all
power transistors.

It's almost like in Turner-world there are no such things as emitter
followers.

No, the problem is you make a claim about "modern transistors" and
then switch to arguing about circuit topology.

You're mistaken, and owe me an apology. The line about "modern
transistors"
came from Trevor, not me.

Then change it to...

Too bad about that character problem you've got, Mr. alias.

No problem, but thanks.

No, the problem is you take the clearly stated
topic "modern transistors" and switch to arguing about circuit
topology.

When you show me a transistor or a tube amplifying audio without a
supporting circuit topology, then and only then will you have made your
point.

My point doesn't depend on a topology, yours did.

Flipper, uour point was first and foremost wrong, because held me
responsible for a comment that Trevor made. You've shown your poor character
by not apologizing for that error, and you've compounded your demonstration
of poor character by continuing to pretend that you have made no mistakes.

You're also callously and deceptively avoiding answering a perfectly
reasonable question about how one can talk about the performance of devices
that must be used in some circuit topology to even have any performance to
discuss.

Please post again when you grow tired of substituting simplistic rhetorical
devices and dissembling for intelligent conversation.

[Andre Jute]

Eeyore wrote:
Andre Jute wrote:

Trevor Wilson wrote:

BTW: Modern transistors are more linear than even the best Triodes.

After the application of a gazlllion dB of kludgeback, sure. And they
sound like it too.

Your absurd obsession with feedback sounding bad is a very tired and entirely
wrong premise based on former poor practice rarely seen any more.

A single sentence from you, Poopie, carrying a whole truckload of
misunderstandings, huge holes in your knowledge, a complete display of
your arrogance, and a tankload of slurry (**** mixed with water, used
for manure).

Your absurd

The only place that it is absurd to want better sound is in the junior
engineers' tearoom. The rest of us know, by just weighing the quality
of the proponents of the status quo, that better sound must be
possible.

obsession

Obsession? Nah, it's my hobby. You are confusing articulate enthusiasm
and glee with something nasty in your own character.

with feedback sounding bad is a very tired

How can it be "tired" for me to say that NFB, the way it is usually
applied in SS devices and big banksa6550 tube amps, mostly sounds like
**** when, at the same time, it is all right for you continuously to
abuse me for expressing a modest opinion?

with feedback sounding bad is a very tired
I want to talk about science and joy -- and you want to talke about
what's fashionable? Poopie, that is disappointing even by your
abysmally low standards.

and entirely
wrong premise based on former poor practice rarely seen any more.

Ah! You admit that for a very long time -- decades -- solid state amps
sounded like ****. So what's your beef with me then? I've always said
the same thing. My solid state amps are Quad 405 II and Audiolab 8000
series, carefully selected for not sounding like majority of
****-silicon. I imagine that, if you could afford them, you would buy
the same silicon amps. So, once more, what is your continuous beef with
me?

rarely seen any more

Crap. Just because a bunch of thick engineers, having been caught out
doing wrong for so long, have now marginally changed their ways does
not mean the principle on which they went wrong has suddenly been made
right.

rarely seen any more

This is like the Russians in 1968 telling me, "Oh, things are better
now. We no longer shoot the statisticians when the numbers don't come
out right." They were constitutionally unable to see that what was
wrong with their system was not the kludges of kludges of kludges but
the very concept of central planning itself, their inability to trust
human nature to find the best answer.

What is wrong with silicon is that it was conceived on the
understanding that massive NFB would be required.

Nothing wrong with NFB in general engineering; I'd hate to drive a
modern car without power steering. But in audio NFB must be used with
the greatest delicacy, or preferably not at all, for it adds artifacts
that make people edgy. That these artifacts are outside present
measuring systems does not make them absent, it merely makes those who
claim that the answer has been found for all time into fools. If in
addition they're fools without delicacy, and furthermore of a bullying
tendency like you, forcing your way in where you are not wanted, I am
justified in calling them silicon slime.

As for the rest of your foolish post, below, I don't do twee little
zero-current preamp tubes. Take the apples out of the orange basket,
gimme a medium-gain example with meaty current and maybe I'll pay
attention to you. Whatever made you think I'm interested in discussing
lowest common denominator guitar tubes?

Andre Jute
Our legislators managed to criminalize fox-hunting and smoking; when
they will get off their collective fat arse and criminalize negative
feedback? It is clearly consumed only by undesirables.


In my example elsewhere in this thread I used 26dB of local feedback ( hardly
gazillions ) to make a transistor's gm equivalent to a 12AX7 for instance. I'll
venture that the transistor circuit is more linear too !

Without doing that, transistors would have vastly more stage gain than any toob,
rendering any meaningful comparison impossible.

Graham

[Patrick Turner]

Arny Krueger wrote:

"Patrick Turner" wrote in message
...


Arny Krueger wrote:

"Patrick Turner" wrote in message
...
Modern transistors are more linear than even the best Triodes.

You have said this misleading statement before.

Unfortunately for your arguments this is not the case with regard to
voltage
gain.
Transistors need only a small range of turn on voltage applied between
their
base and emitter,
and their gm varies enormously between being on the threshold of turn
on
of
collector-emitter current and saturation.

It's almost like in Turner-world there are no such things as emitter
resistors.

I am forced to used Re to linearize bjts....

So what? Re also helps with bias stability.

I am not complaining about having to use NFB.
I have readily used it in the solid state amps I have designed and built.

I am merely saying that NFB is necessary because bjts are not very linear,
and collector resistance is much higher than the loads to which an amp is
connected.

Its negative FB that makes a transistor circuit with fairly non linear devices
linear.
People have said here that SS devices are linear voltage amplifiers.
They are not.
But they do have a lot of gain and NFB can easily be used to provide the
linearity
that is not built into the device.







Only enormous amounts of externally applied NFB corrects the inherent
voltage
non-linearity of all BJTs where there is substantial current change as
in
the case of all
power transistors.

It's almost like in Turner-world there are no such things as emitter
followers.

This is a huge amount of series voltage NFB....

If NFB is such a sonic terror, why did almost every tubed audio amp and
preamp of the days of tubes have it?

A huge % of consumer electronics avoided NFB in preamps because that meant
having gain which could be thrown away, needing extra tubes.
NFB was indeed commonly used in phono amps with two halves of a 12AX7
in countless amps.
But the tone controls and line stages rarely used NFB.
Power amps nearly always had NFB to linearize pentode/tetrode power tubes and
reduce Rout.
I didn't say NFB was a terror, I just said lots of NFB is used in SS amps.

But triode amps can easily be built without global NFB loops and still give low
thd and
great sound.




Try setting up any bjt in common emitter mode without any emitter
resistor
and
apply a voltage from a very low impedance to the base.

Proving once again that if you do something really stupid, you will get
suboptimal results.

I am not here to discuss whether the bjt amp can sound well, or measure
well.
Both are known to be possible so it is believed by most folks.

It's almost like in Turner-world sonic transparancy is the ultimate sin.

I get all the transparancy I want.

So do I. Only, I'm obviously harder to please than you are, Pat.

You are impossible to please.

Patrick Turner.



Why does Arny suggest that i sin with ultimate badness?

I think I just got KROOGERED!

Figure of speech.

Without external loops of NFB including the emitter follower connection
which is a high amount of applied series voltage NFB, the BJT is a
hopeless
voltage amp unless we try to restrict the current change in the device,
and then the gain is
enormous and subject to the perils of the high collector resistance
and
circuit slowness due to capacitances, and the non linear input
resistances
of
other devices in the signal path.

Proving once again that if you do something really stupid, you will get
suboptimal results.

.....Another statement of BS, dislocated from the preceding text....

Not BS, just accepted practice, even in the heyday of tubes, back in the
60s.

[Patrick Turner]

Bret Ludwig wrote:

Andre Jute wrote:



I concluded that, while NFB and Hawksford's variant are both
intellectually fascinating (if you get hold of a better class of
defendant than the clowns here, say for instance someone with brains
and an articulate goodwill to explain difficult concepts to the
innocent like Scott Frankland), for practical audio use they are the
same as going directly to digital.

I'll stick to tubes in simple ZNFB circuits, thanks.


you are so dumb you do not even have the capacity to see your own
case. Power amplifers with either tubes or transistors require
moderate, purposeful applicaton of NFB to not sound cow ****ed when
driving voice coil speakers. Simple as that.

Goodness gracious me, well, really,....
Just what sort of sound does a cow's **** make now....

Any more of that sort of talk and I'll wash you mouth out with soap
and send you to your room.

Patrick Turner

[Trevor Wilson]

"Patrick Turner" wrote in message
...


Eeyore wrote:

Patrick Turner wrote:

Trevor tries to correct Jute's assertions about the perils of NFB but
tells
bigger lies to posture in a worse position.

There is no peril whatever with NFB when intelligently and correctly
applied.

Graham

I happen to agree with you here. I use NFB as I see fit.

But Trevor tried to say there would be little reason why one couldn't
build
a bjt amp without NFB.

**That would be a lie. Here are my EXACT words. Do pay close attention.

ALL AMPLIFIERS USE NFB. EVERY SINGLE ONE.

Understand?



Since he said bjts are so darn linear, then why not dispense entirely with
the NFB?

**Impossible. ALL AMPLIFIERS USE NFB. EVERY SINGLE ONE.



--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

[Trevor Wilson]

"Tom Schlangen" wrote in message
...
Hi Trevor,

BTW: Modern transistors are more linear
than even the best Triodes.

I don't know much about recent transistors, so this
is new to me and sounds interesting.

**When I say recent, I mean post - 1975. The advent of the Ring Emitter
Transistor heralded the advent of spectacularly linear (power) transistors.
Unfortunately, the devices were relatively fragile and not capable of large
current capabilities. However, since the late 1990s, devices have come to
market which offer very impressive linearity, high current capacity and low
cost.


Does it hold true for, for example, comparable circuits,
like building a SE triode or SE transistor amp, both w/o
gNFB?

**Sure, but why would you bother building a crippled amplifier in the first
place? Push pull offers an automatic reduction in even order distortion,
MUCH better load tolerance, higher power output and better efficiency. I see
no point in bothering with SE topology.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com