[Sander deWaal]

"Arny Krueger" said:

"Patrick Turner" wrote in message

I am speaking about the facts of the engineering.


So your example of an SS amp produces 5% THD without
feedback, yet you say that to produce less than 10% is
extremely difficult. I needn't go and measure anything,
I'll just use your example to show that you are being
very silly.


You sound like a man who has NEVER designed or built any
amplifiers, and you are just cruising for a bruising.


Where is your website outlining your achievements and
depth of knowledge?


You mean he loses points for not publicly bragging about himself?

LOL!


Apparently, *I* do lose point for just doing that.

ROTFLMEEEOOOOW !

--

- Maggies are an addiction for life. -

[Sander deWaal]

"Arny Krueger" said:


I find Sander's newfound self-confidence as an "amplifier designer" to be
pretty curious.


That's because you're involved in so many flame wars and lies, you
can;'t even remember who you're responding to at times.


Perhaps Sander can name a store in SE Michigan that has one of his
amplifiers in stock. ;-)

Is Sander's brand name deWaal or what?


Is Graham's brand name "Stevenson"?

--

- Maggies are an addiction for life. -

[Sander deWaal]

"Arny Krueger" said:


Sander often posts pretty incoherently, perhaps testimony to the effects of
the legalization of pot in the Netherlands.


So, what's *your* excuse then? ;-)

--

- Maggies are an addiction for life. -

[Iain Churches]

"Arny Krueger" wrote in message
. ..
"Iain Churches" wrote in message
. fi
"Arny Krueger" wrote in message
. ..
"Iain Churches" wrote in message
. fi
"Sander deWaal" wrote in message
...
"Arny Krueger" said:


Typical of Sander's overly-confrontational approach to
technology he can't properly understand.

ROFL!!

That's why I design amps for a living, and you fix
computers and work on your "usenet career", hmmm? ;-)

I find Sander's newfound self-confidence as an
"amplifier designer" to be pretty curious.

Perhaps Sander can name a store in SE Michigan that has
one of his amplifiers in stock. ;-)

I have just been looking at some archive postings. Sander has some really
excellent posts, made in very good English, which
I know is not his first language.

Sander often posts pretty incoherently, perhaps testimony to the effects
of the legalization of pot in the Netherlands.


Arny, you are probably the last person on RAT entitled to
comment on liguistic incoherence:-)

I remember your "condensor" (sic) microphone, and
your use of KHZ instead of kHz, and DB instead of
dB. Pretty sloppy - even for a cheapo computer
repair man:-)



Iain

[Edward R. Morris]

God IS perfect. You are right on one statement. "Humans are notoriously
erroneous creatures".

Edward Morris

"Patrick Turner" wrote in message
...


The Score So Far,

one says
"********, and illitertate boolocks at that",

two asks,
" ..I wonder what Arnie says?"

three says
"we get weird sound when we get a cold and we type opinions as we type
them.."

four says
that the thesis favoured tube amps at the expense of SS amps,

five said
....."might explain why the empirically arrived at minimum level
necessary for 'undetectable distortion' changed dramatically when
transistors replaced tubes, though."
And five also said a lot of other things which proved he had more
understanding of what Cheever said
about ears, ear distortions and brains.

six said
"For more recent work (2005) along very similar lines but with slightly
different conclusions see
http://www.gedlee.com/distortion_perception.htm

I had a look at that but don't have time right now to read Gedlee's
1.6MB dissertation,


and seven said,
"** Meet the NEW load of ********...
Same as the old load of ********.
( Apologies to Pete Townshend )

Without immediately knowing what relevance Mr Townshend has,
I am at a loss to comment.



TAD, ot Total Audio Discononance is not to be confused with TID,
Transient Induced Distortion.



It seems to me Cheever tries to show that the ears will produce harmonic
voltages from the
hairs in the cochlea in your ear when a pure tone is used as a signal.
The brain he says, filters out the harmonics, and we hear the tone as
pure.

To me this defies common sense, because it implies the brain would do a
lot of filtering
with music or noise which is riddled with many harmonics.
Humans are notoriously erroneous creatures. God isn't perfect, let alone
understandable,
if we take a look at his creations over the millions of years or trial
and error.

But if Cheever is correct, and the brain does away with much of what the
ear microphones feed to it
then its easy to see how MP3 formatted sound gets away with it...

Anyone who has listened to the effects of clipping of clean sine wave in
an amp
would know what the threshold level is for THD of the tone; a 400Hz tone
seems to
suddently become "harder" sounding when the clipping becomes easily
visible on the CRO.
Pop music guitar players would say visibly undistorted sound is dull and
lifeless;
they set their levels so THD is 15% minimum most days...

But Cheever's treatise includes the effect of using NFB in an amp making
10% 2H, and this is not ******** at all; using say 8 dB of NFB around a
gain
stage with 10% THD with no NFB does not improove the sonics even though
the 2H is reduced a bit.

The phenomena of using a very mild amount of NFB, say 5dB to 14dB around
an amp with 10% open loop Dn
and its creation of other harmonics of a higher F has been well
documented in the past.

The past examiners of this phenomena have concluded that where open loop
THD was 10%, and there
was sufficient open loop gain present, ie, the amp wasn't clipping, and
still had considerable headroom
in its output and drive amp stages, then you simply need to apply a lot
more FB
and then all original open loop AND ARTIFACTS CREATED BY THE NFB are
reduced at a constant rate once NFB exceeded about
20dB, and this is shown in Cheever's graphs, if anyone here is able to
read a graph
by looking at it long enough.

Since many SS amps with NFB make THD 0.005% quite routinely at 1 dB
below clipping, and
perhaps 0.001% at say 2 watts, and that open loop THD at 1dB below clip
was 3% typically,
then just how does the ear and brain tell us something is drastically
wrong and make some listeners
go running to the shop for an SET amp?

Surely there have to be limits of audibility of distortion.
If it simply ain't there on the basis of it being totally inaudible if
played to listeners on its own
without the wanted undistorted sound, then how do we perceive the
distortion?

0.001% of say 4Vrms into 8 ohms, 2 watts, makes noise lower than an ant
walking
across the floor in front of the speakers.

I have heard music via SS amps which tend to make a noise similar to
people tearing up
paper in time with the music levels, but many SS amps just don't,
and are as clean as a whistle, so to speak, even clinically clean, too
darn clean in fact for
some listeners, and clean in an objectionable way compared to when they
listen to
a tube amp, which may measure 50 times worse, but nevertheless still
measure quite well with less than 0.04% THD for an SE amp,
and 0.02% for something PP.

I have found it quite easy to make a clean sounding SS amp, and several
that
sound ok when compared to class A tube amps of similar power ceilings
and
low THD at low levels used during continuous actual listening.

I could say that the use of very good passive filtering of rail supplies
in all the amps concerned leads to a clean sound, as well as a high% of
class A working
before the amp moves to class AB helps the NFB do its job.
In many SS amps the noise in the open loop signal is far greater than
the THD/IMD,
so much so that examining the output waveform on a CRO is marred with
hum levels,
even at high output levels.
Reducing the injected PS noise with careful filtering allows the open
loop
to actually be plotted and graphed.
Before NFB is applied many an SS amp then resembles
a giant phono amp which amplifies say 1mV of input to 25Vrms output at
100Hz with bandwidth rolling off
at 6dB/octave after some low F pole which can be as low as perhaps
100Hz.
The open loop response usually includes the local output stage emitter
follower NFB which equates to
typically 40dB of local loop series voltage NFB, ( the definition of the
variety of NFB is important ).
So the response and THD one sees is mainly that created by the class A
bjt input and driver stages.
And if anyone gets that to less than 3% at 25Vrms, they are doing well.
If they also have open loop bandwidth from say 20hz to 5kHz, they are
doing a lot better.

Having an open loop pole at 100Hz means that at if the global NFB is say
60dB at 100Hz, then at 1kHz, its 40 dB,
and at 10kHz its 20 dB, and by 100kHz, there is no effective NFB applied
because gain has dropped to unity.
Just as well, because we get stability more easily.

Its very easy to reduce the 3% of THD to 0.003% with 60dB of GNFB.
My view is that the this 60dB is more effective if there is a low amount
of noise in the signal to begin
with; the applied NFB has an easier task to perform, ie, cleaning out
the spuriae,
which if not cleaned out would leave things sounding worse, surely,
even if by some miracle, we could totally reduce PS noise,
and extend the open loop BW out to 20kHz?
Extending the open loop BW out to 20kHz isn't all that easy with bjts
because we'd have to use either global NFB around the voltage amp gain
stage/s
or have cascaded stages of gain each with its own local FB and when you
have
say 3 gain stages cascaded each not using much NFB, I cannot see how the
spuriae will not be better than if one simple effective GNFB loop is
applied around
ALL 3 cascaded stages.

Amplifiers without emitter follower output stages,
ie, common emitter outputs will have much more open loop THD,
and I cannot see how FB could be dispensed with at all, one other reason
being that
collector resistance like pentode anode resistance or drain resistance
in mosfets gives an amp
with output resistance far to high to be usable, and well above speaker
impedances.

Meanwhile, triodes are passable without any global NFB
and can operate in common cathode and still remain listenable,
and their internal NFB makes them able to have output resistance well
below speaker impedances.

A customer of mine maintains he prefers the sound
of a quad of 300B in PP for each channel without any GNFB.
The NFB is adjustable and he can make the comparisons easily
at the trun of a switch knob.

But we are stuck with distortion regardless of what we do, and the only
way
to avoid it is to attend live music, and where the instruments are NOT
amplified.

Nevertheless I'd swear I was at a concert when I listen to music from
the
local ABC Classic FM radio station here, despite the whole process of
recording onto a CD, replay, sending the signal to a satelite and back,
then encoding
it all to be able to re-constructed into stereo vi a multiplexed 100MHz
carrier,
in my humble all tubed FM tuner, which has switching diodes to create
the stereo,
and the less I tell you all about the process, the better.

My lounge room is never really the best seat in the theatre though,
mainly
because I'm at home, and not out, all dressed up for the occasion, with
friends,
and with the aura of the theatre and human togetherness affecting my
subjective senses.
But plenty of times my lounge room has brought me closer than the best
theatre seat ever could to a performer.
I have plenty of LPs recorded as far back as 1958 which
put me in the same studio room with the artists.

And this luxury is possible despite all that has been said about noise
and distortions.

Patrick Turner.

[Patrick Turner]

Ian Bell wrote:

Patrick Turner wrote:

A real schematic is one that you have drawn up from what you have built
on your breadboard.

Real distortion is what you measured with a meter, and monitored with a
CRO.

I am ONLY interested in REALITY.

You need to work harder to convince me of something here.
Don't forget all the other guys, they are watching you as well.


Really Patrick, I have absolutely no need or desire to convince you of
anything.


I get easily fed up with people who say they don't wanna convince me of
anything.
If that is your attitude, you will never convince yourself of anything,
and nobody else either.

I once had a silly wife who said exactly the same thing and she became
quite a pest to herself
and all the people around her. She could not proove her commitment to
anything.
She was a "whatever" person, and could not be relied upon to attend the
simplest tasks,
and although I tried to reason, plead, cajole, and help her, she wasn't
going to try to help
herself, and finally departed by aeroplane at midnight, away from me,
her job and all she'd known without
letting anyone know, and in a spirit of telling us all with her feet
that we could all go and get ****ed.
I visited her 18mths later after the divorce and property settlment and
she'd gained 3 stone, was smoking
dope all the time, and had become an easy slut.
I finally gave up on her then, and realised once again that you could
talk with some ppl,
but to others it had no effect while they deceived everyone.

I just expect minimum standards of intellectual endeavour in those I
meet on the net.

If you won't take my word for it, build the circuit I provided
and measure it yourself as I have many times in the past.

I need the URL for the schematic, or you can email one to me, less than
100kB, GIF, JPG, PDF,
and NEATLY drawn with all values please, and with all dc working
voltages at least,
and copied from your workshop notebook.

I will not read a long list of numbers and by some damn miracle go
figure out from there.

YOU have to do some real work to make it easy for others to follow your
thoughts.

For me this meant creating a whole website with 18MB of content,
with nearly all the schematics tried and built, de-bugged and fully
tested.


My website is what I have done for ppl like you, so
be so kind as to get busy and work at it.


As for the
SwitchCAD file, it is an excellent simulation package which produces
results that are very close to lab measurements and this one is no
exception. It was simply a convenient means to send you a design you could
check without having to build it yourself or take my word for it. But if
you don't think simulations are at all accurate then I can help you no
further. You can substitute just about any BJT in this circuit and obtain
almost identical results. I know this circuit produces the stated levels of
distortion as well as you know a triode has internal NFB.

Ian

I cannot accept any simulations.
You are being very sloppy and lazy and unless there is some change to
doing all your tests on real devices in the real world, I will never
bother to take much notice of your
"test results".

Guess I will have to do a test again to repeat what i found some years
back.

Patrick Turner.

[Patrick Turner]

KeithR wrote:

Doug Flynn wrote:

Here's what I think:

Pentodes = evil
Global negative feedback = the spawn of Satan
Digitial = the work of the Devil


Pentodes, triodes, and tetrodes = products of the stone age and should be
confined to archaeological digs

Global negative feedback = the first glimmering of hope back in the dark
ages

Digitial = The only way to fly, but setting standards by trying to cram
the longest piece of music available into 640 megs was a bad
idea, mp3s - even worse.

You need to spend a few years building Planet Y out there someplace
where things are perfect enough for you.

We'll be better off when the rocket leaves with you on it.

Patrick Turner.

[Patrick Turner]

KeithR wrote:

Patrick Turner wrote:

Everyone knows just how slimy Arny is, and what an arsole ****head.
Sorry Arny, but you really deserve an award for being a slimy AH.

Again Slimy Arsole lies again.

You are the net's greatest arsole who quickly resorts to telling tales
of BULL**** about what people said, or didn't say.


err, weren't you the one complaining about how Fill goes off when
criticised?

But I have provided long detailed technical replies to back up what I am
saying
in the presence of a severe stream of BS from Arny AH.

Now you are having a go. Just what is your purpose here?

Do you come to learn, share, teach, or just harrass?

Patrick Turner.

[Arny Krueger]

"Sander deWaal" wrote in message

"Arny Krueger" said:

"Sander deWaal" wrote in message

"Arny Krueger" said:

"Sander deWaal" wrote in message

John Byrns said:


The usual outcome: those who like tubes agreed with
most of it, those who loathe tubes disagreed with
most of it.


Typical of Sander's overly-confrontational approach to
technology he can't properly understand.


ROFL!!

That's why I design amps for a living, and you fix
computers and work on your "usenet career", hmmm? ;-)


You design amps for a living, Sander?

Do tell!


Suffering from dementia, Arns?

http://groups.google.nl/group/rec.au...e4ae93 2cf1af
http://groups.google.nl/group/rec.au...2be909 ac1238

And meanwhile, some tube designs of my hand found their
way into production in China under the brand name
"Yarland".

Prove it.

[Arny Krueger]

"Iain Churches" wrote in message
.fi
"Arny Krueger" wrote in message
. ..
"Iain Churches" wrote in message
. fi
"Arny Krueger" wrote in message
. ..
"Iain Churches" wrote in
message
. fi
"Sander deWaal" wrote in message
...
"Arny Krueger" said:


Typical of Sander's overly-confrontational approach
to technology he can't properly understand.

ROFL!!

That's why I design amps for a living, and you fix
computers and work on your "usenet career", hmmm? ;-)

I find Sander's newfound self-confidence as an
"amplifier designer" to be pretty curious.

Perhaps Sander can name a store in SE Michigan that has
one of his amplifiers in stock. ;-)

I have just been looking at some archive postings.
Sander has some really excellent posts, made in very
good English, which I know is not his first language.

Sander often posts pretty incoherently, perhaps
testimony to the effects of the legalization of pot in
the Netherlands.


Arny, you are probably the last person on RAT entitled to
comment on liguistic incoherence:-)

I remember your "condensor" (sic) microphone, and
your use of KHZ instead of kHz, and DB instead of
dB. Pretty sloppy - even for a cheapo computer
repair man:-)

Obsessing over typos in Usenet posts?

You're a really small man, aren't you Iain?

[Patrick Turner]

KeithR wrote:

Patrick Turner wrote:


And in addition to what i said below, there was a brilliant series of
articles
in the 1978-1979 copies of monthly Wireless World on the way in which
low levels
of NFB can make the sound worse.
It was penned by one Peter Baxandall, his part 6 article appears in
Feb'79,
and has very similar graphs of the NFB effects on THD spectra as Mr
Cheever
has drawn, except that Baxandall's efforts look more plausible.
The math involved are at a level fit only for a masochist with lots of
time,
but Baxandall does manage to get the point across regarding applying NFB
and its effect on spectra in THD.
To avoid the worst of what Baxandall and Cheever are saying, it would
seem prudent to
ensuring open loop distortions before NFB is applied be kept well below
the
10% level they use in the examples for their analysis.

Thats kind of interesting, I worked at the same establishment as Peter J in
the early 60s (I was an apprentice, he was THE senior circuit design
consultant). I met him on several occasions and went to a number of his
lectures. At that time he considered a good level of NFB to be essential,
his design for 10 watt EL84 amp published in Wireless World at the time
demonstrated this.

The advice that he gave then was to not bother too much about the amp, NFB
could get the THD low enough not to matter, put very big reservoir
capacitors in the PS to avoid power line droop on peaks (he was an organ
music fan), spend as much as you can on the cartridge and speaker (this was
mono days) because that is where most of your distortion is going to come
from.

Maybe he had a change of heart in his latter days, but when I knew him, the
application of NFB was the heart of his work.


His methods for EL84 amps are just as valid now as they were in 1957.
Accountants in amplifier manufacturing companies never agreed with
people
like Baxandall if there was a cheap nasty way to do things and still be
able
to maintain high sales levels, and all companies reverted to lowest
common denominator crap.

He was right about carts and speakers, and this is still valid today.

In 1957, most speakers were 95dB efficent at 400Hz at least,
and needed little power to go loud.
So amplifier distortions were low, since 1/4 of a watt gave a very loud
89dB from each speaker at a watt, and distortion falls about
proportionately
to output voltage in a substantially class A amp, which nearly all 10
watt EL84 amps were in 1957,
such as the Leak 2020.

Carts varied, some were good, some attrocious, but the Denon MC103
invented in 1949
by Denon was pretty good, and is still good.
1957 speakers were universally crappy unless you were silver tailed and
could afford
ESL57.

Ever plotted a response from any mint condition dynamics from 1957?

I have, and all are quite attrocious. Science may have been very briefly
used to design them,
but during manufacture any semblance of conformity to the science used
in the design
was utterly abandoned, and the public was treated to eating ****
sandwiches for which
they paid a lot of money for. There is still plenty of rip-off right
now,
but in 1957, it was quite rampant, since it was an age of hope, and
fantasies
about purchasing satisfactions of desires for suburban consumeristic
bliss.
Realities shocked ppl, so they looked away.

The stereo Kreisler radiogram my mum bought for a queen's ransom in 1963
had
two 3 watt SE EL84 in pentode amps with
extremely poor circuitry, only 4 dB of NFB which didn't improve the
sound one bit, very inaccurate RIAA,
and the extremely poor Rola speakers were located at each end of the 5'
long floor standing cabinet.
The Rola speakers gagged when asked to make bass from the few new rock
and roll records
my sisters insisted in buying at my parents' great displeasure.
High levels of bass were rude and tasteless in 1957.
The speaker breakup and rising accoustic output when fed from what were
current source amps gave boost to lower and upper F to compensate
partially
for electronic response deficiencies.

The cabinet had a nice finish, and that was why mum was able to be
talked into buying it.
She could have bought a lot better, because she was married to my dad, a
professional man,
a vet, but he may have become upset anyway, because he had a terrible
temper,
and she needed to fear what reaction would occur if she spent too much.
Professional men knew that their wives could make life very financially
miserable without
very much effort in 1960. They earned, their wives spent.
Besides, my dad didn't like music, and couldn't dance.
Mum used to teach piano, and needed music, and why she married a bad
tempered musical clod like dad
remains a mystery. Maybe he was good in bed...
People were desperadoes by the dozen in the 1940s, they didn't wait, and
didn't think.

Buying a full set of Quad gear was simply right out of the question, and
was only for
judges and barristers and prime ministers, and was an utterly frivoulous
expense
because the value of hi-fi in most ppl's minds at the time was not high;
how could it be?,
because nearly everyone based their opinion of hi-fi on the utter
garbage they were being sold,
which was simply to extend simple mantle radio electronics into a
radiogram package.

People tried to buy a better looking lifestyle in 1957, or 63, whenever,
and only the really dogged types who were well educated knew of an
alternative
way of living. Some were condemned as being free thinking communists,
who shocked genteel
society by NOT immeditately marrying and settling down and buying what
was laid out for them
by Dodgy Bros entrepreneurs who only wanted one thing, their money.
I was one such shocking examples of the brash young men about, I waited
10 years before marrying,
and rejected most things others foolishly did, and it wasn't until
1976 I bought any hi-fi, a passable SS receiver. First TT was a Sansui
212, and with Shure M91ED MM.
I had lots of good parties with that lot. I have always built my own
speakers,
and have the pair I made 31 years ago, rebuilt twice now, but the bass
drivers are still wonderful.
The mids and trebs were quickly retired when I got some measuring gear
and some Vifa midranges in 1993.
The bass function sounds well if the response is curtailed to 250Hz,
anything higher as ppl did in 1970
sounded like strident mud, but ppl tried to not have to buy a good
midrange.
Bass surrounds for the 12" Foster bass drivers are woven cotton doped
with rubber, and have no signs
of deteriation. Its the only pair of speakers I have ever seen with such
a suspension system,
I must have spotted the superiority in '76 straightawy; I was an
observant young turk.
The two drivers cost $30 each, so about a weeks pay for the two, or
equal to spending $700 now.
It was worth it; you should have seen the other crap being sold!!!!
I went to a local district library in 1976 and copied the design for a
bass reflex
from RDH4, which I found on a shelf. When building anything, I thought,
study well first.
One needs a 3 way system for full range sound, IMHO.
If I had had more time in 1976, I'd have built my own tube amps. But I
was doubling the size of the house
I'd bought, and building all my own furniture. The silly young wife also
needed a fair amount of fixin,
so building amps as well all looked like too many ruined sundays, and I
had a reasonable wage,
and although most THOUGHTFUL ppl thought tubes were nice, they knew SS
could do near enough to what tubes did
if you didn't have the money or time....
The receiver was a 30W/ch Linear Design, I still have it but the Oz
company has gone broke a long time ago.
It cost $200 in 1976, but that was half the price of a supposedly better
Marantz receiver capable of the same power.
$400 in 1976 was about a month's pay, or equal to maybe $4,000 now, and
Marantz sure laughed all the way to the bank,
because by then Marantz were having things made very cheaply in asian
sweatshops.
I didn't like big business much either. **** Marantz is what i thought.
The 30 watts per ch was more than what I ever needed at a party, and
seemed like a lot of power then.
Neither myself or my friends were deaf.

Patrick Turner.

[Patrick Turner]

John Byrns wrote:

In article ,
Patrick Turner wrote:

John Byrns wrote:

In article ,
Patrick Turner wrote:

I think I prefer the sound of the radio stations that have NFB built
into their carrier modulators,
so that at the station a receiver module produces audio from the
radiated RF signal,
then compares that with the audio used to modulate the RF signal, and
applies an error signal to reduce
N&D to sub audible levels.
I am wondering if I would like the whole transmission done without any
loop FB,

Did you actually check out what sorts of "carrier modulators" the
various radio stations were actually using, so that you can truthfully
say you have correlated the sound of the stations with the "carrier
modulators" they used? It's probably too late to do this experiment
today, what with digital modulation schemes having taken over the field.
Assuming that you actually investigated what sort of "carrier
modulators" were being used by the stations you preferred, as well as
those you didn't, how did you eliminate the possibility that it wasn't
the overall loop negative feedback that produced the sound you liked,
but was some other factor common to the transmitters using overall loop
negative feedback? I can think of one factor that is common to most
analog transmitters that didn't use overall loop negative feedback, i.e.
demodulated RF, that I suspect was more likely to have contributed to
your dislike of them.

What i do know is that for present AM and FM transmissions in Oz the
waves must remain compatible for existing analog receivers to
decode audio from the RF carrier waves, and the recovered audio cannot
be more linear than the transmitter modulator permits,
and so I have assumed modulators have inbuilt means to use NFB to
ensure modulation is as linear as possible. Engineers have told me but
I admit I have not seen ths latest transmitters' schematics and analysed
them.

The "Digital" AM transmitters I was speaking of were not the so called
"Digital Radio" types. What I was talking about were AM transmitters
that use digital techniques to produce an analog waveform "compatible
for existing analog receivers to decode audio from the RF carrier
waves". These are essentially large high power RF D to A converters,
that take a digital audio input from an A to D converter, CD player, or
whatever, and use it to drive the large RF D to A converter which
directly drives the antenna through a filter/matching network.

OK, I am light years behind developments in radio transmitter design.

Lets just say NFB used to be used, and is still used where old
transmitters exist.

linearity is still of concern to engineers no matter how they prepare a
modulated
RF carrier for reception by existing radios.

I was assuming that you were talking about the old style AM tube
transmitters. Many of these used high power class B audio amplifiers to
modulate the final RF stage in the transmitter. This type of
transmitter used negative feedback from the plates of the high power
push pull modulator tubes back to the audio input stage, this feedback
did not encompass the large modulation transformer or the modulated RF
stages. I am not aware of any transmitters of this type that apply
negative feedback around the entire transmitter from a detector
connected to the RF output. The feedback stability problems were
apparently just too great.

You may find the stability problems are not all that great, AM needs
only 9kHz BW max here in Oz,
and less in Japan.

Many transmitters did employ loop feedback from an RF detector.
Typically transmitters of the following types used feedback from an RF
detector.

1. Low level modulation followed by high power linear amplifiers.

2. Screen modulated Tetrode final RF amplifier.

3. Low/medium level modulation followed by a triode Doherty high
efficiency linear amplifier.

4. Chireix outphasing modulation.

5. Screen modulated Tetrode Weldon Doherty high efficiency final
amplifier.

I suspect that what you were hearing was not the negative feedback of
the transmitters in the second group, but rather were the artifacts
produced by the high power class B audio stage in the first type of
transmitter.

One radio engineer once told me his task each night was to test the
transmitter for less than 2% THD in the signal with a 1kHz sine wave.
At between 1AM and 3AM, many stations could be heard running their test.


My personal favorite is the screen modulated tetrode final with overall
negative feedback from an RF detector.

Your'e moving along to distortion in RF ampfiers.

Most here are not much interested in anything else except audio amps.

If you want to build a really low thd RF oscillator with say an AM
function
to allow between say 0% and 100% modulation levels of a tone, its not
hard to
make one up which uses NFB to linearize the modulation to an extent
where
the receiver demodulation THD/IMD will always be higher, unless
rather extraordinary measures are taken with RF and IF amplifications
and AM detection methods.

Another approach the ancients used was to start with an ordinary AM
generator that would produce the required low level of distortion at say
30% modulation, and then mix in enough out of phase carrier signal to
bring the overall modulation level up to 100%. This yields a low
distortion RF signal generator capable of low distortion at 100%
modulation.

How many crates of tubes and coils and trim caps does that all take?

However if you push the modulation beyond 100%, this
generator does not clip the negative peaks like the common AM envelope
modulator, instead the carrier flips phase on the negative modulation
peaks, sort of like an DSB-SC modulator. The result is that an envelope
detector will show higher distortion with this type of generator when
the modulation is push past 100%, than it will with a standard AM RF
generator. On the other hand a synchronous detector will demodulate
this signal without distortion, even when it is over modulated. A
corollary of this is that if this sort of modulation scheme were used in
an actual broadcast transmitter, over modulation would not cause
sideband splatter into adjacent channels as it does with the common AM
envelope modulator.

AM is the poor relation of the media industry.
Nobody gives a ****; what is cheapest and easy to maintain is king.

I once tried a tubed "synchrodyne receiver" but turned to a wide
bandwdth
superhet for more easily obtained good resuslts.

I don't have time now.

Patrick Turner.

Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Patrick Turner]

John Byrns wrote:

In article ,
Patrick Turner wrote:

John Byrns wrote:

Where is the schematic for your proposal?

My scanner is broken so my verbal description will have to do.

For example take 11 identical BJts
and connect 10 of them in parallel.

But is this for a power application? preamp?, what?

I was thinking of it as a preamp, but it could be either. In fact your
mention of using it "for a power application" has got me thinking that
it might be a way to build a BJT amplifier without negative feedback for
the "Pinko" challenge. I will have to look up the ground rules for the
"Pinko" challenge, take pen, paper, and calculator in hand, and see if I
can come up with a workable solution.

For an SE power app, think about a darlington triple input.
Then think of a CCS dc supply instead of 10k collector R.

Maybe you end up with a ByrnZen amplifier.
But mosfets are so much easier to drive than any BJT.....

[Snip]

OK, I think I have drawn up the schematic easily enough from what you
have said.

I knew you could do it.

you have 10 parallel npn BJT in common emitter which is grounded.
Input AND bias from a low Z source is via series 10k to the 10 bases.
Output from the 10 collectors.

an 11th npn BJT is also set up with emitter grounded, but its base and
collector
both connected to the other 10 bases, so in effect the 11th BJT is a
Baxandall diode,

What might I ask is a "Baxandall diode"?

Its a transistor used as a diode, base in connected to collector,
so the BJT is turned on fully when passing current, and the threshold of
turn on
is the same as another BJT. Baxandall invented the idea and his name is
applied when a BJT is used
like this.

and for some reason you are perhaps suggesting that as the base input
voltage rises,
so does the current in the 11th BJT, as it does in the other 10 BJT, and
you'd get a linear
voltage outcome.

Correct, but don't forget the series input resistor.

It is part of a shunt NFB network.

Patrick Turner.

Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Patrick Turner]

"Edward R. Morris" wrote:

God IS perfect. You are right on one statement. "Humans are notoriously
erroneous creatures".

Edward Morris

There is always one, maybe two, in every crowd
who hears a large amount about what he is here for then picks
on what is not so obvious, and of little concern to
us humans, ie, God's perfection.

I recall singing a line of a folksong, a long time ago,

"God does love me I don't think,
If he did he'd buy me a drink"

Apparently, if I were to believe the born again Christian Right
I should buy God a drink, although drink is not a correct type of gift,
not for any god, even when it looks like he needs a very stiff drink, to
get him
relaxed at such a hard job all day creating then managing the Universe,
and putting up with all the mistakes he made, and those of the sinners
he created.
All seems a bit pointless to make a universe with built in obsolesence,
that needs to spend billions of years before parts of evolve self
consciousness,
and being able to ask "why the **** it is all here God?"

The One True Truth is that God is unknowable, because He is infinite,
and we only have tiny teenzy weeny brains to comprehend Him, and all the
information NOT IN THE BIBLE
won't fit into such brains, so there's no need to try, you will fail,
and whether God is perfect or not
is mere conjecture, a social convention during pleasant discourse.

Ppl say God Is Perfect because they are placing a safe bet.
Better to Praise the Lord despite evidence he doesn't deserve it just in
case
you end up having to face Him later.
One won't get into heaven if you turn up after
spending one's time down here casting ill favour upon the Lord.
But I have never catowed before anyone and won't ever.
I don't care if I go to hell. Hell, I been told to go there
often enough...

Its like bad mouthing the bank manager. He darn well knows what you
think
and when you ask for a loan, you'll know why he said " NO."

I see the Universe as SNAFU.

Meanwhile, courtesy of Chance, autumn days here are glorious, long
bicycle rides are nice,
music is great, not much distortion to worry about,
women my age are a complete waste of time,
I'd like to be a little richer, but I don't mind povety.
Life isn't too bad, not even tree bad, and if God isn't perfect, I
understand,
because neither am I.

Patrick Turner.

[KeithR]

Patrick Turner wrote:

err, weren't you the one complaining about how Fill goes off when
criticised?

But I have provided long detailed technical replies to back up what I am
saying
in the presence of a severe stream of BS from Arny AH.

Now you are having a go. Just what is your purpose here?

Do you come to learn, share, teach, or just harrass?

I am here for my own amusement. The sight of (presumably) grown men
endlessly arguing over the same ground as my friends and I did when we were
teenaged apprentice electronics designers is rather sad but funny at the
same time. Most of us moved on and decided that it was better to listen to
the music than to the equipment and that there is a law of diminishing
returns with regards to what you spend on music reproduction systems.

What is not so edifying is the sight of a bunch of cronies egging on someone
with obvious mental problems, kind of like bear baiting.

In your case, I was pointing out the hypocrisy of complaining about insults
from others and then slinging them yourself. I doesn't matter how right or
wrong you are, slinging insults is not a valid argument technique, it
usually indicates that the slinger has run out of logical points and is
just throwing in noise to cover the fact. You do come across as arrogant,
fixed in your views, and unwilling to concede anything, this makes you a
target for the loonies and makes it less likely that others will accept
your arguments.

[John Byrns]

In article ,
Patrick Turner wrote:

John Byrns wrote:

In article ,
Patrick Turner wrote:

John Byrns wrote:

Where is the schematic for your proposal?

My scanner is broken so my verbal description will have to do.

For example take 11 identical BJts
and connect 10 of them in parallel.

But is this for a power application? preamp?, what?

I was thinking of it as a preamp, but it could be either. In fact your
mention of using it "for a power application" has got me thinking that
it might be a way to build a BJT amplifier without negative feedback for
the "Pinko" challenge. I will have to look up the ground rules for the
"Pinko" challenge, take pen, paper, and calculator in hand, and see if I
can come up with a workable solution.

For an SE power app, think about a darlington triple input.
Then think of a CCS dc supply instead of 10k collector R.

The 10k collector resistor was for the simple preamp circuit. I have
thought about using a CCS, and actually used one in a BJT SE power
amplifier I built that predates the "Pinko" challenge which doesn't meet
the rules of the "Pinko" challenge. I am leaning towards an output
transformer for the "Pinko" challenge.

As far as "darlington triples" go, the "darlington triple" includes two
emitter followers which have a shirt load of negative feedback, and so
are not allowed by the rules of the "Pinko" challenge.

Maybe you end up with a ByrnZen amplifier.
But mosfets are so much easier to drive than any BJT.....

[Snip]

OK, I think I have drawn up the schematic easily enough from what you
have said.

I knew you could do it.

you have 10 parallel npn BJT in common emitter which is grounded.
Input AND bias from a low Z source is via series 10k to the 10 bases.
Output from the 10 collectors.

an 11th npn BJT is also set up with emitter grounded, but its base and
collector
both connected to the other 10 bases, so in effect the 11th BJT is a
Baxandall diode,

What might I ask is a "Baxandall diode"?

Its a transistor used as a diode, base in connected to collector,
so the BJT is turned on fully when passing current, and the threshold of
turn on
is the same as another BJT. Baxandall invented the idea and his name is
applied when a BJT is used
like this.

and for some reason you are perhaps suggesting that as the base input
voltage rises,
so does the current in the 11th BJT, as it does in the other 10 BJT, and
you'd get a linear
voltage outcome.

Correct, but don't forget the series input resistor.

It is part of a shunt NFB network.

And where is the other part of the shunt NFB network, the feedback part?
And if this series resistor causes shunt NFB, what do you do if a preamp
with a finite source impedance is used to drive the power amp? Or what
if the CD player in the "Pinko" challenge has an isolation resistor in
the output lead?


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Patrick Turner]

KeithR wrote:

Patrick Turner wrote:

err, weren't you the one complaining about how Fill goes off when
criticised?

But I have provided long detailed technical replies to back up what I am
saying
in the presence of a severe stream of BS from Arny AH.

Now you are having a go. Just what is your purpose here?

Do you come to learn, share, teach, or just harrass?

I am here for my own amusement. The sight of (presumably) grown men
endlessly arguing over the same ground as my friends and I did when we were
teenaged apprentice electronics designers is rather sad but funny at the
same time. Most of us moved on and decided that it was better to listen to
the music than to the equipment and that there is a law of diminishing
returns with regards to what you spend on music reproduction systems.

What is not so edifying is the sight of a bunch of cronies egging on someone
with obvious mental problems, kind of like bear baiting.

In your case, I was pointing out the hypocrisy of complaining about insults
from others and then slinging them yourself. I doesn't matter how right or
wrong you are, slinging insults is not a valid argument technique, it
usually indicates that the slinger has run out of logical points and is
just throwing in noise to cover the fact. You do come across as arrogant,
fixed in your views, and unwilling to concede anything, this makes you a
target for the loonies and makes it less likely that others will accept
your arguments.

If you don't have the internal courage to take part in a debating forum,
stay away.

If you think of us all with contempt, stay away,

If you have nothing to offer, stay away.

And if you cannot see why I am not shy to pick up some **** and rub it
right into the
eyes of offenders when i see fit, stay away.
Its not very often I have to climb into the cess pit to clean it.
If I tread on a few low life critters while I'm there, so be it,
and I know how to clean up later.

All government debates in the House of Lords, Aust. Parliment, US House
of Reps,
Russian Parliment are all places where the mud flies.

Most days I dodge the lot, and come home clean.

Meanwhile, I plan to stay here, and won't miss you if you have nothing
constructive to say.

If you think I am arrogant because I hold my ground, never willing to
concede
anything, always remember I don't agree with bull**** easily, you know,
all those pet ideas
that simply don't add up, or are confusingly presented for
consideration.
Its you who will tell me I am arrogant, but you adopt the stance that
you know everything, and
had the same conversations 50 years ago. YOU ARE ARROGANT YOURSELF to be
such a ****ing hypocrite
and come here accusing any of us.

If you want to convince me of anything, then you have to put some real
effort in,
and show respect.

Meanwhile there have been many times when I have more to say to the
group about audio related engineering
than the rest of group put together, something most don't seem to mind.

Just what benefit to tubecraft have you ever been?

The group has suffered many distractions with off topic crap talks, but
a high SNR
on news groups has become normal ever since the Internet became
mainstream.
Unmoderated groups were to attract social misfits whose ONLY human
connection would be possible in a news group
from where it is difficult to dislodge them.

I don't like the other little private groups because they are full of
peole who rarely ever
fill a screen with their thoughts, and who hate ever being challenged.

If you want a nice looking audio group, try the moderated
rec.audio.high-end,
where the conversations are stultifyingly dull most days, and where you
have to wait days before
you may see a posted reply, and where there isn't much DIY.


Patrick Turner.

[Patrick Turner]

For an SE power app, think about a darlington triple input.
Then think of a CCS dc supply instead of 10k collector R.

The 10k collector resistor was for the simple preamp circuit. I have
thought about using a CCS, and actually used one in a BJT SE power
amplifier I built that predates the "Pinko" challenge which doesn't meet
the rules of the "Pinko" challenge. I am leaning towards an output
transformer for the "Pinko" challenge.

OK, if you have a CCS for the collector load, the Rout without any NFB
is the dynamic collector resistance, and is very high, like a pentode.
The load becomes the open loop Rout.

With an OPT connected to a collector circuit, you will have appallingly
high
transformer caused distortions because its fed by a current source.
Only the load reduces the Dn.
But if you have NFB, this works to reduce Dn and the effective Rc,
and all the tranny distortions, as it does with a pentode amp.

As far as "darlington triples" go, the "darlington triple" includes two
emitter followers which have a shirt load of negative feedback, and so
are not allowed by the rules of the "Pinko" challenge.

OK, the first BJT of a darlington pair does indeed act as a follower
device
with a shirtload of local series NFB, just like a 12AX7 when set up as a
cathode follower.

But there is no other way to easily increase input resistance other than
using some kind
of NFB somewhere, and in a BJT amp, one must think
of using NFB freely to get anywhere.
If you are to say that you will limit the NFB total to 12dB, like in a
Nelson Pass Zen amp,
or about equal to the amount of internal triode NFB in a loaded 300B SET
amp,
then you have a real challenge.



Maybe you end up with a ByrnZen amplifier.
But mosfets are so much easier to drive than any BJT.....

[Snip]

OK, I think I have drawn up the schematic easily enough from what you
have said.

I knew you could do it.

you have 10 parallel npn BJT in common emitter which is grounded.
Input AND bias from a low Z source is via series 10k to the 10 bases.
Output from the 10 collectors.

an 11th npn BJT is also set up with emitter grounded, but its base and
collector
both connected to the other 10 bases, so in effect the 11th BJT is a
Baxandall diode,

What might I ask is a "Baxandall diode"?

Its a transistor used as a diode, base in connected to collector,
so the BJT is turned on fully when passing current, and the threshold of
turn on
is the same as another BJT. Baxandall invented the idea and his name is
applied when a BJT is used
like this.

and for some reason you are perhaps suggesting that as the base input
voltage rises,
so does the current in the 11th BJT, as it does in the other 10 BJT, and
you'd get a linear
voltage outcome.

Correct, but don't forget the series input resistor.

It is part of a shunt NFB network.

And where is the other part of the shunt NFB network, the feedback part?
And if this series resistor causes shunt NFB, what do you do if a preamp
with a finite source impedance is used to drive the power amp? Or what
if the CD player in the "Pinko" challenge has an isolation resistor in
the output lead?

Where you have a series R in front of the base input, you will have a
voltage across that
R = the R x Iout/hfe.

The base current = collector current/hfe.

This is a substantially linear relationship. So any change in voltage at
RL at the collector
will involve a change in current in the collector circuit which is in
series with RL.

So therefore you get a corresponding change in base input current. So
-1V at the collector
caused by some external factor means IRL is greater, so Ib is greater,
and because you have 10k in series with Ib, the voltage signal at the
base
falls with increasing current in the 10k, and a falling base voltage
tends to
make less current flow in the base thus opposing the externally cause
increase in current.
So the output current change due to distortion is opposed by the
fraction of fed back
current in shunt with the input current.

Where the source input is very low R, much lower than the actual
measured base input resistance,
no such shunt current NFB correction can occur.
Thus Dn is very high.

All BJTs operate so that current conduction from collector to emitter
begins when Vbe
is about 0.4V, and the device saturates when Vbe = about 0.75V.
Between the two voltage points the gm of the BJT varies enormously, as
does the
measured small signal base input resistance which resembles a simple
silicon diode
turn on chracter.

There are many here who do not want to contemplate these very awkward
facts about BJTs.

I can only suggest that everyone who is curious about BJTs should hook
one up and measure what they observe,
and let us know. I keep telling people, find out for yourself, I won't
do YOUR HOMEWORK.

More info is at

http://www.google.com/search?sourcei...basic+working+

Very many misunderstandings and mental blocks occur in DIYers who refuse
to teach themselves about the basics.

Patrick Turner



Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Ian Bell]

Patrick Turner wrote:

diatribe snipped


I will not read a long list of numbers and by some damn miracle go
figure out from there.


I told you it was a SwitcherCAD file. All you have to do is run SwitcherCAD
and load the file - the circuit will then be seen complete with all
component values.



I cannot accept any simulations.
You are being very sloppy and lazy and unless there is some change to
doing all your tests on real devices in the real world, I will never
bother to take much notice of your
"test results".


You obviously missed the bit where I said I have built this circuit many
times in the past.

Guess I will have to do a test again to repeat what i found some years
back.



If you use the same circuit you will get the same results. If you use the
circuit I have given you you will get the results I described. Why don't
YOU make some effort, download switcherCAD -it's free (I cannot believe you
don't know of its existence) load in the file I posted then YOU build it
and prove my results are wrong.

Ian

[Patrick Turner]

Ian Bell wrote:

Patrick Turner wrote:

diatribe snipped


I will not read a long list of numbers and by some damn miracle go
figure out from there.


I told you it was a SwitcherCAD file. All you have to do is run SwitcherCAD
and load the file - the circuit will then be seen complete with all
component values.


I refuse to load a program to view your "work".


I cannot accept any simulations.
You are being very sloppy and lazy and unless there is some change to
doing all your tests on real devices in the real world, I will never
bother to take much notice of your
"test results".


You obviously missed the bit where I said I have built this circuit many
times in the past.

Guess I will have to do a test again to repeat what i found some years
back.


If you use the same circuit you will get the same results. If you use the
circuit I have given you you will get the results I described. Why don't
YOU make some effort, download switcherCAD -it's free (I cannot believe you
don't know of its existence) load in the file I posted then YOU build it
and prove my results are wrong.

I have never used simulation software. I did try to use some software
for circuits,
but the programme writers couldn't explain it properly and I always had
too many questions that i could not ask
because PCs don't often give answers. It was much easier to walk out to
my workshop and
build a real circuit, rather than waste 10 hours ****ing around on a PC,
and maybe getting fooled in the process, because a couple of important
details
han't been included in the program.
And there are no programs which acurrately predict output transformers,
and none that cover all the design and LCR properties properly, so I
studied it all the hard way and
really did become an expert on the subject, and I sell my results in
amplifiers i make.

My brain, CRO, meters and soldering iron are the tools I use to solve
problems and gain undertsanding.

I will re examine the THD of a single BJT, we all need a refresher
course sometimes,
but I will use my schematic, not yours,
because you have not presented it anywhere so one click will have it on
my screen.
In other recent posts I have clearly explained how to set up a test to
show
the working distortion of a single small signal BJT.
I intend expanding my web pages to include more about bjts and j-fets,
so that the basics become more obvious.
Late last year I built a complete SS phono stage which I need to
transfer to the electronic medium for the Web.
This will take days to re-draw in MS Paint so when lazy critters like
you pay a visit,
you won't be misled, the information will all be there and nothing is
bull****.
There is a more that DIYers should about SE j-fets and SE bjt preamp
stages
to make music more enjoyable, IMHO.

I have never needed anyone to tell me much about anything electronic; I
always find out for myself,
since I have learnt to NEVER trust anyone because of the bull****
factor.
I did for years before going online in 2000, and have for years since.

You need someone to light a fire under your arse to get you away from
your PC and
to a soldering iron and the real world,
where real devices are examined.

I make no apologies for being a ******* over the issue, but where I come
from we learn
things properly, lest we end up ignorant, and mistaken.

Patrick Turner.





Ian

[Ian Bell]

Patrick Turner wrote:
I will re examine the THD of a single BJT, we all need a refresher
course sometimes,
but I will use my schematic, not yours,
because you have not presented it anywhere so one click will have it on
my screen.


OK click on this and you will see it.

http://i103.photobucket.com/albums/m...ds/patrick.jpg

Now I challenge you to build and test it and publish the results.

Ian

[Ian Bell]

Ian Bell wrote:

Patrick Turner wrote:
I will re examine the THD of a single BJT, we all need a refresher
course sometimes,
but I will use my schematic, not yours,
because you have not presented it anywhere so one click will have it on
my screen.


OK click on this and you will see it.

http://i103.photobucket.com/albums/m...ds/patrick.jpg

Now I challenge you to build and test it and publish the results.

Ian

And by the way, there is a deliberate mistake in the circuit. Let's see if
you can find it.

Ian

[Phil Allison]

"Ian Bell"

And by the way, there is a deliberate mistake in the circuit.


** The load resistor " R5 " is too low in value.

Limits the output swing.



....... Phil

[Ian Bell]

Phil Allison wrote:


"Ian Bell"

And by the way, there is a deliberate mistake in the circuit.


** The load resistor " R5 " is too low in value.

Limits the output swing.



...... Phil

Whilst that is true, it is deliberate rather than a mistake. It was put
there in response to an earlier post of Patrick's. The circuit still works
fine with that value of R5.

There is another, much more serious error.

Ian

[tubegarden]

On Mar 21, 3:16?pm, "Edward R. Morris" wrote:


three says
"we get weird sound when we get a cold and we type opinions as we type
them.."


err, I typed: "we form opinions as we type them"

Not that anyone reads long posts

Just how much coffee do you guys drink?

Happy Ears!
Al (three)

[Patrick Turner]

Ian Bell wrote:

Patrick Turner wrote:
I will re examine the THD of a single BJT, we all need a refresher
course sometimes,
but I will use my schematic, not yours,
because you have not presented it anywhere so one click will have it on
my screen.

OK click on this and you will see it.

http://i103.photobucket.com/albums/m...ds/patrick.jpg

Now I challenge you to build and test it and publish the results.

Ian


I'm glad you are still talking to me. Hundreds of less courageous ppl
would have ignored me.

That schematic appeared fine with one click, and that's more like it.

Before I try it, I need to just talk about a couple of things.

The issue we were discussing was concerning BJTs and their Voltage
linearity,
which you say is good because you get low THD from this circuit.

Have I got you right? I hope so, because I can't sleep if I misrepresent
anyone.

Now in your circuit you would have what I have to assume to be
a low impedance signal source feeding a 10uF dc blocking cap followed by
a
high R bias divider circuit, and a series 33k resistor to the base.
The emitter is effectively grounded for ac, the collector load is
the 47k dc load, with 50k ac load in parallel, which makes a total ac
load = approx 24k.
The bias circuit R are effectively tight coupled to the sig gene, so we
may ignore there
presence for now.

The data on the 2n3904 is at

http://www.fairchildsemi.com/ds/2N/2N3904.pdf

The dc gain hfe could be anywhere between about 70 and 300 for when Ic =
1.5mA,
and temp is about room temp, but let us suppose hfe is 100.
( BJTs are not like tubes, their characteristics vary with batches and
temperature,
so its not much use having fixed data....)

Allow me to guess at what we might measure in your circuit if we had
the meters able to do it without the sometimes low voltages being
obscured by
hum and noise. Noise drew me to many wrong conclusions, until i learnt
to measure things without
adding noise, shunting the signal i wanted to measure, or causing
oscillations, or all 3.

This means that if you have say 2.4Vrms at the collector output, load
current Ic = 0.1mA.

So base current will be 1/100 of this, = 0.001mA.

To get this much current change into the base via the 33k, you need a
voltage across the 33k =
33k x 0.001mA = 0.033Vrms.

Let us assume the base input resistance was say 2k.
I have no idea exactly what it would measure, just like I have no idea
what the collector resistance is either.
These parameters are not just nicely listed in the data, of if they are
it will be obtained by reading the many
graphs for the device, but to really know, you have to measure it.

So if you have 0.033Vrms input across the 33k, and you have 2k from base
to 0V,
then there must be a voltage change at the base of 2,000 x 0.001mA, so
the base ac voltage = 0.002Vrms, not much, and the VOLTAGE gain between
base and
collector = 2.4V / 0.002V = 1,200.

The voltage at the source will be 0.033Vrms + 0.002vrms = 0.035Vrms, and
so voltage gain between source and collector output = 2.4 / 0.035 =
68.6, a dramatically lower
amount of gain than actually exists between the base and the collector.
The relationship between the collector current and base current is
essentially linear, in fact as
linear as the voltage amplification in a triode.
But lets not confuse voltage linearity with current linearity.

Suppose a -ve distortion voltage appears at the collector.

Call it -Dn. Then you will have an IDn, and at the base, IDn / 100 will
flow because
all currents that flow at the collector are all divided down by the hfe
figure.
A -Dn V causes MORE Ic, so you will get MORE Ib, so Idn at the base will
cause the base voltage to
tend to go negative, tending to turn off the bjt, and to cause the
collector voltage to rise,
as Ic and IRL becomes LESS. In other words, the tiny fraction of the
output distortion current
that flows in RL is applied to the base automatically to oppose its own
production,
and this is shunt NFB in action, and quite a bit too there is.

Now, suppose you place a link across the 33k, and increase the input cap
from 10uF
to 1,000uF, and make sure the signal generator output resistance is 10
ohms, then
you will prevent the negative current FB from acting, since the input R
has been reduced to
negligible levels. What you will see now is a heck of a lot more gain,
probably about 1,200 like I said you would, but a lot more distortion in
the collector signal and as you crank up
the input voltage so output = 15Vrms, possible with a +60V dc supply,
the distortion should be quite bad.

Looking at the situation more simply, 33k only has 0.033Vrms across it
to give 2.4vrms output.

The amount of base current change is tiny!, so we say that the input is
being fed by a
virtual 'current' source.
And it because the 33k is so much larger than the resistance load it
powers, ie, the base input resistance.

In a tube, Rin to the grid is many megohms, and not easily measured, so
a 33k series grid R can still be called
low impedance signal source, or a 'voltage' source.
In a tube circuit, a 33k series grid R has no NFB function, since no
current flows in it.

In another recent post by John Byrns, the same proposition has been made
about
building a BJT amp with no NFB, but his intitial idea had a 10k series
base input R, which is a FB element.
If you want to improve on the outcome of your circuit and want a gain of
only 10, for a line stage,
then you could connect another resistance from the base to collector as
an extra FB element in addition
to the internal resistance between collector and base that exists.

The first time I connected up a BJT without any series R from signal
gene to base the
THD was appalling, and very soon when I inserted a series R to measure
the base input resistance
the distortion went a lot lower, along with the gain. Hmm, I thought,
NFB.

To raise base input resistance to a maximum, because it varies with
collector load, one can use an emitter follower buffer
from the collector, and have a CCS dc supplyto the collector, but then
the dc stability will be lousy,
so one answer is to have a -60V supply, and extend the emitter
resistance of say 100k,
while leaving the 1,000uF emitter bypass cap where it is.
Still you will find Rb in to be too low, so a darlington pair should be
used, and for really nice work,
use only darlington pairs for gain devices, with a dp for emitter
follower, and finally you will begin to see the
silicon shine, and the base to collector gain will maybe go up to 5,00,
and far more than you would ever need,
and so will the THD.
But simple shunt resistance from the dp follower emitter to input base
of the gain dp
will control runaway gain and you will have a stage with extremely low
THD.
But its all due to NFB, not the inherent voltage linearity of the BJT,
which does not exist;
such linearity is a triode owned thing, because of the triode internal
NFB which you cannot
include in any external loop like you can with currents around a BJT.

I could tell about doing a µ-follower circuit with bjts instead of
triodes,
and such a stage with shunt NFB will work just great, and local current
NFB can be
used in the emitter circuit and THD can be somewhat tailored by choosing
the collector load to the bottom gain pair.

J-fets have high Rin like tubes, and do not have such a thing as a hfe,
or base resistance and so can be treated exactly like
small pentode tubes, with a gm, Rd, and µ.

The 2sk369 at Id = 5mA has gm = 40mA/V, Rd = 80k, and µ = 3,200. However
with mant high gm fets and mosfets
with high gain, the miller C need only be 5pF drain to gate, abd if gain
= 1,000,
then C Miller = 0.005uFm way to high for most audio apps.

BJTs also have Miller C and other bandwidth limiting issues, and input
stage gain should be tailored to maintain
high Rin, and low Cin.

Patrick Turner.

[Patrick Turner]

Phil Allison wrote:

"Ian Bell"

And by the way, there is a deliberate mistake in the circuit.

** The load resistor " R5 " is too low in value.

Limits the output swing.

...... Phil


Indeed this is true, and R5 should be 2.2M, or left out altogether.
but for the analysis of the circuit I just tendered, it won't make any
difference if R5 is left as 50k.

Look, when Ian tests the circuit, he will find out about ac/dc load
ratios for widest v-swings.


If the 50k is removed, gain should increase somewhat.
But by how much do you guys think it will rise?

If there is 2.4Vrms at the collector, with both 47k and 50k loads, and
then the 50k is removed without altering the input level, and the signal
rises to 3.0Vrms,
what conclusion can you come to?


Patrick Turner.

[John Byrns]

In article 4602719b.0@entanet, Ian Bell
wrote:

Patrick Turner wrote:
I will re examine the THD of a single BJT, we all need a refresher
course sometimes,
but I will use my schematic, not yours,
because you have not presented it anywhere so one click will have it on
my screen.


OK click on this and you will see it.

http://i103.photobucket.com/albums/m...ds/patrick.jpg

Now I challenge you to build and test it and publish the results.

What is R6 doing in there? Patrick has already made it clear that
adding a series resistor in the input circuit is cheating and is not
allowed.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Patrick Turner]

Ian Bell wrote:

Phil Allison wrote:


"Ian Bell"

And by the way, there is a deliberate mistake in the circuit.


** The load resistor " R5 " is too low in value.

Limits the output swing.



...... Phil

Whilst that is true, it is deliberate rather than a mistake. It was put
there in response to an earlier post of Patrick's. The circuit still works
fine with that value of R5.

There is another, much more serious error.

Ian

The R3 590k bias resistor needs to be a much lower value.
Maybe 330k; R3 should be adjusted for Ec = 30V with a pot, the pot value
measured,
then the pot replaced with a fixed resistance
because having pots with dc that can be jarred or
moved while tangling around on a breadboard is a PITA.

But if only 1.0Vrms is wanted from such a circuit you can cheat a bit
with a BJT and
increase bias current by reducing R3, or increasing R4, and having Ec at
say +15V, and the extra Ic will
place the device into a better class A position.

2N3904 has a collector-base breakdown voltage of 60V, and rail voltage
is +60V.
I doubt the device will break down because RL is 47k, and limits Ic, and
R6, 33k,
limits base input current, but extreme voltage swings will be distorted.

a rail of +40V is plenty.
Otherwise use a higher rated bjt.

I have assumed R7, 47k at the input to be an input R put there for not
paticular reason.
decoration perhaps, but it need not be present for analysis.

If you have a sig gene at the input it shunts the 47k if its Rout = 600
ohms "generator" or "source resistance".

Patrick Turner.

[Patrick Turner]

tubegarden wrote:

On Mar 21, 3:16?pm, "Edward R. Morris" wrote:

three says
"we get weird sound when we get a cold and we type opinions as we type
them.."


err, I typed: "we form opinions as we type them"

Not that anyone reads long posts

Just how much coffee do you guys drink?

Happy Ears!
Al (three)

Yes but you unplug tubes after you've grown them in your garden,
and put them in bases like flowers in vases,
and its all a very nice day where you are isn't it Al,
and hang in there mate because they don't makem like they used to
anymore.


I like Italiano de grond coffee grounda in Ozza, lotsa bootifull
grinders here.

I make him up in de Mocca on de stove, she boil, she steam, she gurglo,
she hava a Roma, multo bella segnor, et segnoras.

Er sumtimes I putta de grappa in de cuppa, it give a bigga boosta to the
de life.

meanwhile, itta help de opinione de intelegenzzi, le tuba craftori.

Patrica Turnera.

[John Byrns]

In article ,
Patrick Turner wrote:

Ian Bell wrote:

There is another, much more serious error.

Ian

The R3 590k bias resistor needs to be a much lower value.
Maybe 330k;

How do you figure that, 590k seems about right to me? I would go with
560k for R3. So we have three choices, 590k, 560k, and 330k, which is
the worst choice?

R3 should be adjusted for Ec = 30V with a pot,

An Ec of 30 volts is too high for optimal large signal performance.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Iain Churches]

"Arny Krueger" wrote in message
. ..

OTOH, I was probably my own scratch-designed tubed power amps before Iain
learned how to solder.

????


I was more concerned with irregular verbs in
Latin and Greek, and classical music theory
at that time.

My tutor said, "A classical education is the best way to
ensure you do not end up a computer repair man in
SE Michigan:-)

Iain

[Iain Churches]

"Arny Krueger" wrote in message
...
"Iain Churches" wrote in message
.fi
"Arny Krueger" wrote in message
. ..
"Iain Churches" wrote in message
. fi
"Arny Krueger" wrote in message
. ..
"Iain Churches" wrote in
message
. fi
"Sander deWaal" wrote in message
...
"Arny Krueger" said:


Typical of Sander's overly-confrontational approach
to technology he can't properly understand.

ROFL!!

That's why I design amps for a living, and you fix
computers and work on your "usenet career", hmmm? ;-)

I find Sander's newfound self-confidence as an
"amplifier designer" to be pretty curious.

Perhaps Sander can name a store in SE Michigan that has
one of his amplifiers in stock. ;-)

I have just been looking at some archive postings.
Sander has some really excellent posts, made in very
good English, which I know is not his first language.

Sander often posts pretty incoherently, perhaps
testimony to the effects of the legalization of pot in
the Netherlands.


Arny, you are probably the last person on RAT entitled to
comment on liguistic incoherence:-)

I remember your "condensor" (sic) microphone, and
your use of KHZ instead of kHz, and DB instead of
dB. Pretty sloppy - even for a cheapo computer
repair man:-)

Obsessing over typos in Usenet posts?


The way people write, in addition to what they write
gives a very useful insight. A man like yourself, who claims
an engineering background, does nothing to enhance his
credibility with such a low level of accuracy. If you can't even be
bothered to write the units of measurement correctly,
how could we possibly believe any formulae or
calculations you might post? :-)

It's a good thing you are not a professional pianist, Arny
"Oh I played D minor 7, that should have been
E flat diminished. Oh, what the hell. Close enough" :-))

Iain

[Edward R. Morris]

Patrick,
Since you pride yourself on being so smart; so intellectual, what other
sources do you have about God, other than the Bible?

Edward Morris

"Patrick Turner" wrote in message
...


"Edward R. Morris" wrote:

God IS perfect. You are right on one statement. "Humans are notoriously
erroneous creatures".

Edward Morris

There is always one, maybe two, in every crowd
who hears a large amount about what he is here for then picks
on what is not so obvious, and of little concern to
us humans, ie, God's perfection.

I recall singing a line of a folksong, a long time ago,

"God does love me I don't think,
If he did he'd buy me a drink"

Apparently, if I were to believe the born again Christian Right
I should buy God a drink, although drink is not a correct type of gift,
not for any god, even when it looks like he needs a very stiff drink, to
get him
relaxed at such a hard job all day creating then managing the Universe,
and putting up with all the mistakes he made, and those of the sinners
he created.
All seems a bit pointless to make a universe with built in obsolesence,
that needs to spend billions of years before parts of evolve self
consciousness,
and being able to ask "why the **** it is all here God?"

The One True Truth is that God is unknowable, because He is infinite,
and we only have tiny teenzy weeny brains to comprehend Him, and all the
information NOT IN THE BIBLE
won't fit into such brains, so there's no need to try, you will fail,
and whether God is perfect or not
is mere conjecture, a social convention during pleasant discourse.

Ppl say God Is Perfect because they are placing a safe bet.
Better to Praise the Lord despite evidence he doesn't deserve it just in
case
you end up having to face Him later.
One won't get into heaven if you turn up after
spending one's time down here casting ill favour upon the Lord.
But I have never catowed before anyone and won't ever.
I don't care if I go to hell. Hell, I been told to go there
often enough...

Its like bad mouthing the bank manager. He darn well knows what you
think
and when you ask for a loan, you'll know why he said " NO."

I see the Universe as SNAFU.

Meanwhile, courtesy of Chance, autumn days here are glorious, long
bicycle rides are nice,
music is great, not much distortion to worry about,
women my age are a complete waste of time,
I'd like to be a little richer, but I don't mind povety.
Life isn't too bad, not even tree bad, and if God isn't perfect, I
understand,
because neither am I.

Patrick Turner.

[Eeyore]

John Byrns wrote:

In article 4602719b.0@entanet, Ian Bell
wrote:

Patrick Turner wrote:
I will re examine the THD of a single BJT, we all need a refresher
course sometimes,
but I will use my schematic, not yours,
because you have not presented it anywhere so one click will have it on
my screen.


OK click on this and you will see it.

http://i103.photobucket.com/albums/m...ds/patrick.jpg

Now I challenge you to build and test it and publish the results.

What is R6 doing in there? Patrick has already made it clear that
adding a series resistor in the input circuit is cheating and is not
allowed.

R6 is going to introduce a lot of signal loss and introduce a beta depence
factor in the gain equation. Very bad design.

Graham

[Ian Bell]

John Byrns wrote:



What is R6 doing in there? Patrick has already made it clear that
adding a series resistor in the input circuit is cheating and is not
allowed.



How can that possibly be called cheating?

Ian

[Ian Bell]

Patrick Turner wrote:

The R3 590k bias resistor needs to be a much lower value.
Maybe 330k; R3 should be adjusted for Ec = 30V with a pot, the pot value
measured,
then the pot replaced with a fixed resistance
because having pots with dc that can be jarred or
moved while tangling around on a breadboard is a PITA.


It's fine as it is. The output sits at about 22V, quite satisfactory for a
+- 12V swing.

There is just under 59V across the 590K and about 1.5V across the 15K.

But if only 1.0Vrms is wanted from such a circuit you can cheat a bit
with a BJT and
increase bias current by reducing R3, or increasing R4, and having Ec at
say +15V, and the extra Ic will
place the device into a better class A position.


This circuit will happily drive 9V rms into the 50K. I know I have built and
tested it.

2N3904 has a collector-base breakdown voltage of 60V, and rail voltage
is +60V.
I doubt the device will break down because RL is 47k, and limits Ic, and
R6, 33k,
limits base input current, but extreme voltage swings will be distorted.

a rail of +40V is plenty.

That is the deliberate mistake.

Otherwise use a higher rated bjt.

I have assumed R7, 47k at the input to be an input R put there for not
paticular reason.
decoration perhaps, but it need not be present for analysis.


Correct.


Ian

[Ian Bell]

Patrick Turner wrote:



Ian Bell wrote:

Patrick Turner wrote:
I will re examine the THD of a single BJT, we all need a refresher
course sometimes,
but I will use my schematic, not yours,
because you have not presented it anywhere so one click will have it on
my screen.

OK click on this and you will see it.

http://i103.photobucket.com/albums/m...ds/patrick.jpg

Now I challenge you to build and test it and publish the results.

Ian


I'm glad you are still talking to me. Hundreds of less courageous ppl
would have ignored me.

That schematic appeared fine with one click, and that's more like it.

Before I try it, I need to just talk about a couple of things.

The issue we were discussing was concerning BJTs and their Voltage
linearity,
which you say is good because you get low THD from this circuit.

Have I got you right? I hope so, because I can't sleep if I misrepresent
anyone.

Now in your circuit you would have what I have to assume to be
a low impedance signal source feeding a 10uF dc blocking cap followed by
a
high R bias divider circuit, and a series 33k resistor to the base.
The emitter is effectively grounded for ac, the collector load is
the 47k dc load, with 50k ac load in parallel, which makes a total ac
load = approx 24k.
The bias circuit R are effectively tight coupled to the sig gene, so we
may ignore there
presence for now.

The data on the 2n3904 is at

http://www.fairchildsemi.com/ds/2N/2N3904.pdf

The dc gain hfe could be anywhere between about 70 and 300 for when Ic =
1.5mA,
and temp is about room temp, but let us suppose hfe is 100.
( BJTs are not like tubes, their characteristics vary with batches and
temperature,
so its not much use having fixed data....)

Allow me to guess at what we might measure in your circuit if we had
the meters able to do it without the sometimes low voltages being
obscured by
hum and noise. Noise drew me to many wrong conclusions, until i learnt
to measure things without
adding noise, shunting the signal i wanted to measure, or causing
oscillations, or all 3.

This means that if you have say 2.4Vrms at the collector output, load
current Ic = 0.1mA.

So base current will be 1/100 of this, = 0.001mA.

To get this much current change into the base via the 33k, you need a
voltage across the 33k =
33k x 0.001mA = 0.033Vrms.

Let us assume the base input resistance was say 2k.
I have no idea exactly what it would measure, just like I have no idea
what the collector resistance is either.
These parameters are not just nicely listed in the data, of if they are
it will be obtained by reading the many
graphs for the device, but to really know, you have to measure it.

So if you have 0.033Vrms input across the 33k, and you have 2k from base
to 0V,
then there must be a voltage change at the base of 2,000 x 0.001mA, so
the base ac voltage = 0.002Vrms, not much, and the VOLTAGE gain between
base and
collector = 2.4V / 0.002V = 1,200.

The voltage at the source will be 0.033Vrms + 0.002vrms = 0.035Vrms, and
so voltage gain between source and collector output = 2.4 / 0.035 =
68.6, a dramatically lower
amount of gain than actually exists between the base and the collector.
The relationship between the collector current and base current is
essentially linear, in fact as
linear as the voltage amplification in a triode.
But lets not confuse voltage linearity with current linearity.

Suppose a -ve distortion voltage appears at the collector.

Call it -Dn. Then you will have an IDn, and at the base, IDn / 100 will
flow because
all currents that flow at the collector are all divided down by the hfe
figure.
A -Dn V causes MORE Ic, so you will get MORE Ib, so Idn at the base will
cause the base voltage to
tend to go negative, tending to turn off the bjt, and to cause the
collector voltage to rise,
as Ic and IRL becomes LESS. In other words, the tiny fraction of the
output distortion current
that flows in RL is applied to the base automatically to oppose its own
production,
and this is shunt NFB in action, and quite a bit too there is.

Now, suppose you place a link across the 33k, and increase the input cap
from 10uF
to 1,000uF, and make sure the signal generator output resistance is 10
ohms, then
you will prevent the negative current FB from acting, since the input R
has been reduced to
negligible levels. What you will see now is a heck of a lot more gain,
probably about 1,200 like I said you would, but a lot more distortion in
the collector signal and as you crank up
the input voltage so output = 15Vrms, possible with a +60V dc supply,
the distortion should be quite bad.

Looking at the situation more simply, 33k only has 0.033Vrms across it
to give 2.4vrms output.

The amount of base current change is tiny!, so we say that the input is
being fed by a
virtual 'current' source.
And it because the 33k is so much larger than the resistance load it
powers, ie, the base input resistance.

In a tube, Rin to the grid is many megohms, and not easily measured, so
a 33k series grid R can still be called
low impedance signal source, or a 'voltage' source.
In a tube circuit, a 33k series grid R has no NFB function, since no
current flows in it.

In another recent post by John Byrns, the same proposition has been made
about
building a BJT amp with no NFB, but his intitial idea had a 10k series
base input R, which is a FB element.
If you want to improve on the outcome of your circuit and want a gain of
only 10, for a line stage,
then you could connect another resistance from the base to collector as
an extra FB element in addition
to the internal resistance between collector and base that exists.

The first time I connected up a BJT without any series R from signal
gene to base the
THD was appalling, and very soon when I inserted a series R to measure
the base input resistance
the distortion went a lot lower, along with the gain. Hmm, I thought,
NFB.

To raise base input resistance to a maximum, because it varies with
collector load, one can use an emitter follower buffer
from the collector, and have a CCS dc supplyto the collector, but then
the dc stability will be lousy,
so one answer is to have a -60V supply, and extend the emitter
resistance of say 100k,
while leaving the 1,000uF emitter bypass cap where it is.
Still you will find Rb in to be too low, so a darlington pair should be
used, and for really nice work,
use only darlington pairs for gain devices, with a dp for emitter
follower, and finally you will begin to see the
silicon shine, and the base to collector gain will maybe go up to 5,00,
and far more than you would ever need,
and so will the THD.
But simple shunt resistance from the dp follower emitter to input base
of the gain dp
will control runaway gain and you will have a stage with extremely low
THD.
But its all due to NFB, not the inherent voltage linearity of the BJT,
which does not exist;
such linearity is a triode owned thing, because of the triode internal
NFB which you cannot
include in any external loop like you can with currents around a BJT.

I could tell about doing a µ-follower circuit with bjts instead of
triodes,
and such a stage with shunt NFB will work just great, and local current
NFB can be
used in the emitter circuit and THD can be somewhat tailored by choosing
the collector load to the bottom gain pair.

J-fets have high Rin like tubes, and do not have such a thing as a hfe,
or base resistance and so can be treated exactly like
small pentode tubes, with a gm, Rd, and µ.

The 2sk369 at Id = 5mA has gm = 40mA/V, Rd = 80k, and µ = 3,200. However
with mant high gm fets and mosfets
with high gain, the miller C need only be 5pF drain to gate, abd if gain
= 1,000,
then C Miller = 0.005uFm way to high for most audio apps.

BJTs also have Miller C and other bandwidth limiting issues, and input
stage gain should be tailored to maintain
high Rin, and low Cin.

Patrick Turner.

There's a lot to think about there Patrick. I've saved the post and I'll get
back to you.

Ian

[John Byrns]

In article 46030633.0@entanet, Ian Bell
wrote:

John Byrns wrote:



What is R6 doing in there? Patrick has already made it clear that
adding a series resistor in the input circuit is cheating and is not
allowed.



How can that possibly be called cheating?

The reason Patrick gives is that R6 greatly increases the negative
feedback in the circuit and his original premise was that the BJT
circuit couldn't use negative feedback. Patrick has posted on this
issue several times already.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[paul packer]

On Thu, 22 Mar 2007 17:47:14 +0200, "Iain Churches"
wrote:


"Arny Krueger" wrote in message
...

OTOH, I was probably my own scratch-designed tubed power amps before Iain
learned how to solder.

????


I was more concerned with irregular verbs in
Latin and Greek, and classical music theory
at that time.

My tutor said, "A classical education is the best way to
ensure you do not end up a computer repair man in
SE Michigan:-)

Iain

How wise that man was! :-)