On Fri, 31 Mar 2006 20:11:39 GMT, (Don Pearce)
wrote:

On 31 Mar 2006 12:06:03 -0800, " wrote:

I do happen to have the "Bartok Quartet" recordings of Beethoven's
string quartets. Sadly, it is a marginal recording technically and not
a fair test of any system. Not the same thing, for sure but you
triggered a memory.

Well, it does have to be a super-nice recording.

As my primary test pieces, I use a Kiri Te Kanawa recording of various
classical and baroque pieces giving a good deal of solo soprano voice.
She has a lot of color in her voice, more-so than most sopranos and can
reach well down into the contralto-range. Done right, she is 'right
there' and breathing. Done wrong and I picture her on a stage about
fifty feet away.

I find Kiri a bit affected in her vowel sounds - very hard to
establish what is "right" from her voice, I find. Got any old Emma
Kirkby?

I use Kiri's Chants d'Auvergne on Decca as a purity check, but Rickie
Lee Jones for emotion. If 'Easy Money' and 'Coolsville' don't get me
in the back of the throat, I ain't buyin' those speakers!

Also solo trumpet and solo harpsichord. I am overly fond of baroque
trumpet.

For full-range, the Saint-Saens Organ Symphony will reach well down
into the nether regions, yet demand clarity up top. If the systems pass
the above test, then I trot out this last. If I can pick out the
parts-and-sections of the orchestra, great. If I hear lots of mud,
not-so-great.

That will do nicely.

Indeed, probably the finest of all single check pieces. I also use
Carmina Burana to check separation of voices in the choir.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

" wrote:

John:

OK. So, what you are writing is that clipping off half the sine wave
will have no effect on the secondary voltage, or it will drop it to
zero, depending on the orientation of the diode? This due to the nature
of the rectifier used?

And apart from that, have you found an application other than the one
in question where such 'ballast' resistors are used? That is, apart
from home-brew necessities adapting not-quite-suited parts to a
particular purpose?

Careful about using the word "sophisticated" in this application.

Function: adjective
Etymology: Medieval Latin sophisticatus
1 : not in a natural, pure, or original state : ADULTERATED a
sophisticated oil
2 : deprived of native or original simplicity: as a : highly
complicated or developed : COMPLEX sophisticated electronic devices b
: having a refined knowledge of the ways of the world cultivated
especially through wide experience a sophisticated lady
3 : devoid of grossness: as a : finely experienced and aware a
sophisticated columnist b : intellectually appealing a sophisticated
novel

One has to go pretty far down for a positive definition, and as the
goal is KISS, even that seems in direct conflict with the stated goal
in any case.

Peter Wieck
Wyncote, PA

There is a way the single diode could be used to cut the volts out of the
rectifier in half, but only if the filter network is choke input. But you
don't need the extra Si Diode.

Just hook one of the tube rectifier plates to the common lead. It becomes
the so-called 'free wheeling' diode, as in switch mode power supplies. But
now the rectifier is half-wave & we have DC biasing of the PT.

But why bother going further with this half-baked amplifier? It is the
effort of an amateur.

My opinion, anyway. John Stewart

"Don Pearce" wrote in message
...
On 31 Mar 2006 12:06:03 -0800, " wrote:

I do happen to have the "Bartok Quartet" recordings of Beethoven's
string quartets. Sadly, it is a marginal recording technically and not
a fair test of any system. Not the same thing, for sure but you
triggered a memory.

Well, it does have to be a super-nice recording.

As my primary test pieces, I use a Kiri Te Kanawa recording of various
classical and baroque pieces giving a good deal of solo soprano voice.
She has a lot of color in her voice, more-so than most sopranos and can
reach well down into the contralto-range. Done right, she is 'right
there' and breathing. Done wrong and I picture her on a stage about
fifty feet away.

I find Kiri a bit affected in her vowel sounds - very hard to
establish what is "right" from her voice, I find. Got any old Emma
Kirkby?

Emma K was signed to Decca, while I was there. I worked with her
often with Anthony Rooley. She was an exceptional talent, and her
interpretation of Dowland was second to none. She was charming
with the most beautiful thick red hair. I was totally smitten:-)

Female voice with piano/harpsichord makes excellent test material.

Also solo trumpet and solo harpsichord.

Agreed.

I am overly fond of baroque
trumpet.

I too. There are some fantastic works
by little know composers such as Andrea Grossi, Giovanni
Buonamente, Giovanni Coperario who wrote wonderfully for
both Baroque trumpet and cornetto. I have worked quite a
lot with both Don Smithers and John Wilbrahams.
John was a virtuoso on the Eb ("piccolo")
trumpet. Recordings by either of these artists make excellent
evaluation material.

For full-range, the Saint-Saens Organ Symphony will reach well down
into the nether regions, yet demand clarity up top. If the systems pass
the above test, then I trot out this last. If I can pick out the
parts-and-sections of the orchestra, great. If I hear lots of mud,
not-so-great.

Yes indeed. Something majestic. Widor: Op42 (Simon Preston.
Liverpool Metropolitan Cathedral Organ) fits the bill nicely.


Iain

"Don Pearce" wrote in message
...
On 31 Mar 2006 11:32:10 -0800, " wrote:

Vivaldi Mandolin
Moltor Trumpet

Nice transition from Mozart to Beethoven and beyond: Johann Nepomuk
Hummel, with specific reference to his Mandolin and Trumpet works.

Done right and at a resonable volume, a test of any system.

Ellington, definitely. Ives, at the right time and mood. Arne, I have
not acquired that taste, but neither have I rejected it...

So much great music, so little time.

Peter Wieck
Wyncote, PA

All great music, I'm sure - but I wouldn't use any of those to test a
system; they are far too musically dense. They are really hard to hear
past to see what the system is like.


I thought we were talking about what we listen to, not what we use
for evaluation - two totally different things:-)

But I agree with Peter's choice of Hummel. The Bassoon Concerto
is an excellent test piece, as are the Quartet and Quintet in Eb.


For musical testing I favour Bartok quartets - get a nicely staged
recording and you will find both physical and tonal space between all
the instruments that will reveal the actual quality of the system.

For small ensemble, you cannot beat the Shostakovich Quartets.
For something small and dynamic my show reel contains Stravinski:
The Soldier's Tale. Then you need something to thunder, and not too
modestly (:-)) Mussogrsky is the man for that. Pictures as an Exhibition
(orchestration by Ravel) is most revealing.

For system testing I use speech, from friends - both male and female.
That is a really severe test, and very few systems actually sound like
my friends.

Hmm. Interesting idea:-) Two flaws. Few people have the equipment
to record a voice with accuracy (a Tandberg will not do:-) to make it
suitable for any kind of evaluation. Secondly, so few people are used
to hearing the sound of there own voice that the speaker him/herself
cannot take part in the evaluation.


Iain

On Sat, 1 Apr 2006 15:36:37 +0300, "Iain Churches"
wrote:


"Don Pearce" wrote in message
...
On 31 Mar 2006 12:06:03 -0800, " wrote:

I do happen to have the "Bartok Quartet" recordings of Beethoven's
string quartets. Sadly, it is a marginal recording technically and not
a fair test of any system. Not the same thing, for sure but you
triggered a memory.

Well, it does have to be a super-nice recording.

As my primary test pieces, I use a Kiri Te Kanawa recording of various
classical and baroque pieces giving a good deal of solo soprano voice.
She has a lot of color in her voice, more-so than most sopranos and can
reach well down into the contralto-range. Done right, she is 'right
there' and breathing. Done wrong and I picture her on a stage about
fifty feet away.

I find Kiri a bit affected in her vowel sounds - very hard to
establish what is "right" from her voice, I find. Got any old Emma
Kirkby?

Emma K was signed to Decca, while I was there. I worked with her
often with Anthony Rooley. She was an exceptional talent, and her
interpretation of Dowland was second to none. She was charming
with the most beautiful thick red hair. I was totally smitten:-)

I saw Emma and Anthony on vocal and lute many times at Wigmore hall. I
can't say I enjoyed the acoustics, though :-(

Female voice with piano/harpsichord makes excellent test material.

Also solo trumpet and solo harpsichord.

Agreed.

I am overly fond of baroque
trumpet.

I too. There are some fantastic works
by little know composers such as Andrea Grossi, Giovanni
Buonamente, Giovanni Coperario who wrote wonderfully for
both Baroque trumpet and cornetto. I have worked quite a
lot with both Don Smithers and John Wilbrahams.
John was a virtuoso on the Eb ("piccolo")
trumpet. Recordings by either of these artists make excellent
evaluation material.

For full-range, the Saint-Saens Organ Symphony will reach well down
into the nether regions, yet demand clarity up top. If the systems pass
the above test, then I trot out this last. If I can pick out the
parts-and-sections of the orchestra, great. If I hear lots of mud,
not-so-great.

Yes indeed. Something majestic. Widor: Op42 (Simon Preston.
Liverpool Metropolitan Cathedral Organ) fits the bill nicely.

Why not go for it - his toccata, for instance. Pure cheese!

d

Pearce Consulting
http://www.pearce.uk.com

"Don Pearce" wrote in message
...
On Sat, 1 Apr 2006 15:37:27 +0300, "Iain Churches"
wrote:


"Don Pearce" wrote in message
.. .
On 31 Mar 2006 11:32:10 -0800, " wrote:

Vivaldi Mandolin
Moltor Trumpet

Nice transition from Mozart to Beethoven and beyond: Johann Nepomuk
Hummel, with specific reference to his Mandolin and Trumpet works.

Done right and at a resonable volume, a test of any system.

Ellington, definitely. Ives, at the right time and mood. Arne, I have
not acquired that taste, but neither have I rejected it...

So much great music, so little time.

Peter Wieck
Wyncote, PA

All great music, I'm sure - but I wouldn't use any of those to test a
system; they are far too musically dense. They are really hard to hear
past to see what the system is like.


I thought we were talking about what we listen to, not what we use
for evaluation - two totally different things:-)

Not where I came in - that was definitely evaluation.

But I agree with Peter's choice of Hummel. The Bassoon Concerto
is an excellent test piece, as are the Quartet and Quintet in Eb.


For musical testing I favour Bartok quartets - get a nicely staged
recording and you will find both physical and tonal space between all
the instruments that will reveal the actual quality of the system.

For small ensemble, you cannot beat the Shostakovich Quartets.
For something small and dynamic my show reel contains Stravinski:
The Soldier's Tale. Then you need something to thunder, and not too
modestly (:-)) Mussogrsky is the man for that. Pictures as an Exhibition
(orchestration by Ravel) is most revealing.

They would all do nicely.

For system testing I use speech, from friends - both male and female.
That is a really severe test, and very few systems actually sound like
my friends.

Hmm. Interesting idea:-) Two flaws. Few people have the equipment
to record a voice with accuracy (a Tandberg will not do:-) to make it
suitable for any kind of evaluation. Secondly, so few people are used
to hearing the sound of there own voice that the speaker him/herself
cannot take part in the evaluation.


But not for me - I do have the equipment. And of course I would never
use the sound of my own voice - I have no idea what I sound like to
that degree of accuracy.

d

Pearce Consulting
http://www.pearce.uk.com


I agree, the human voice is an excellent test and I have the recording
equipment also. The Organ Symphony & 1812 etc are also valid, I've recorded
Carol Kidd (with permission) that was also a good test...

Mike

In your long post to put peter right, I come across this....


Two chokes? Why?

Because that is how one builds a choke input supply. It cannot be
wound/specified/built more economically (Patrick?) or efficiently in
terms of smoothing than as two (equal) sections.

The use of LCLC in a B+ power supply does offer the good smoothing.

The choke values and following C values of the LC circuits have to be chosen
carefully to avoid any undamped
resonances. In the case where you have 10H, 51uF, Fo = 7Hz, and for the
second LC with 10H and 100uF, Fo = 3.5Hz,
and both F are low enough.
The ac voltage at twice the mains F, say 100Hz, at the input to the choke1
from rectifiers = 0.67 x 400 = 268Vrms,
and L1 C1 has an attenuation factor of 31 / 6,280 = 0.0049, so at C1, Vripple
= 1.31Vrms.
The attenuation of L2 C2 = 16 / 6,280 = 0.0025 so ripple at C2 = 0.0032 Vrms,
quite low enough to not
inject much noise into the OPT because the output triode tube has low Ra, 800
ohms, and the load will maybe 5k, so nearly all the hum from the C2 is across
the OPT.

The use of 10H chokes to cope with 130mA is uneconomical when compared to
just using CLC, or even CRC,
where the value of C1 and C2 is 470uF x 450V rated caps with a 300 volt
winding for an SS bridge rectifier.
with about 320vrms for the HT you can afford to have 50 ohms at 20W rating to
limit high charge currents to the caps,
and the GZ34 is better used as a slow turn on diode, ahead of the R or L in
the CRC filter.

The circuit of the PS at
http://members.lycos.co.uk/fiultra/T...trafi-crct.jpg
has a traditional set up apart from having 1/2 the rectifiers in tube for
slow turn on and the other 1/2 in SS.

I am not against tradition should anyone want to be traditional.

Consider a CRC for say 120mA at 400V. There is no bleed current.

Regardless of the series R to limit peak charge currents into C, and
therefore reduce dissipation in the B+ winding,
Vripple at C1 470uF = 0.56 Vrms.

We want to get down to match the LCLC supply, ie, have Vr = 3mV.

So the attenuation factor must be 0.003 / 0.56 = 0.0053, say 0.005.

CRC requires that R *or* ZL = ZC / 0.005 = 3.4 / 0.005 where C = 470uF for
C2.

so R = 680 ohms, or L = 1.08H.

Now 120mA would give a V drop of 81V dc across the R, and so Vin at C1 would
have to be +480V,
and too high to be able to use a single 470 uf cap rated at 450V at C1.

But the choke would be fine. Fo for LC = & Hz, low enough, but any choke of
more than 1.5h will do.

But we could also employ CRCRC perhaps. If the total attenation factor needed
0.005,
then each RC section needs to have attenuation of the square root of 0.005 =
0.071,
so R needs to be 3.4 / 0.071 = 47 ohms, and dcV drop is only 5V.
We may use say a GZ34 plus 22 ohms for R1, and 47 ohms for R2, and we have a
decent
supply without any chokes, no bleed current, slow turn on, efficient use of
transformer, and no resonant LC behaviour.

if CRCRCRC was used, the requirement is that R 10 x ZC, so 39 ohms is
plenty, and attenuation factor
= 0.1 x 0.1 x 0.1 = 0.001, and ripple at C4 1mV.
The benefit with 470uF is that it is a mightly nice low Z anchor from which
the SE OPT is hooked up to.

If you insist on two chokes, then if C = 470 uF, then you are goverened by
resobance because if you had
ZL = say 100 ohms, or 63mH, then Fo = 29Hz, way too high.

Using say 2 to 3 Henrys with CLC is far cheaper than using x 10H chokes imho.

In my SEUL amp where Idc out = 220mA, I used CLC with C1 = 340uF, C2 = 235uF
and L = 9H, a monster
C cored choke, so Fo 5Hz, and all is well.

I have used GZ32 in reformed Quad II where it is a slow turn on series diode
with R = 90ohms when on
and where Idc = 130mA. But it isn't necessary because output tubes come on
slower than the GZ32, or 34,
and B+ soars a bit anyway. With 300B though, the cathode warms up quite fast,
and the slow turn on does give a
nice delay, but really it isn't a hiuge benefit.
The better thing is to have the output tubes sit there with heaters going to
2 minutes without any B+ so as to allow the
gas molecules to be absorbed by the gettering before the B+ is applied when
the gas becomes +ve charged ions which then bombard the cathode. That's the
theory anyway..

But then when the B+ does come on with hot cathodes, you tend to get an Idc
surge, but I doubt it causes any problems.
The large Cs will have the B+ rise fairly slowly anyway...

Chokes were used in older PS mainly because C values were hopelessly high
since electros were
temperamental. And the swinging choke was de-riguer for supplies to PP amps
working in mainly
class B ( or class C in transmitters ) because Idc varies with signal level
and CLC with tube rectifiers
caused attrocious variations in B+ with power levels.
The RDH4 graphs of regulation with LC filters ( with the optional second LC )
shows that the swinger choke is far better
than the same rectifier and output current range than CLC let alone CRC.

PP amps could get away without any more than one LC input filter because the
PP output stage tends to
reject the hum while working in class A, which they do for most of the music.

SE amps need both a quiet supply and a low impedance at the OPT connection.
regulation does not matter and in fact wwith plenty of series R then charge
up of the large caps involved is a peaceful process and if an output tube
shorts you want a cheap R to go open before a choke or OPT winding does.

So the R used for power supplies should not be too rugged, just rugged
enough.


There is more than one way to do it all, happy choking if you must, its
theraputic thay say....







The 5AR4 is a pretty good, quite rugged (if expensive)
rectifier.

So what? I'm specifying a couple of grand's worth of tubes already.
Anyway, it sounds better than semiconductor diodes and lasts longer too
unless you heatsink diode bridges properly.

In the T39 the GZ34 will be replaced with a GZ37, which will really
hurt if you worry about costs!

And it would seem simpler to add additional capacitance on
the line-side of the first choke, thereby eliminating the need for the
second?

The idea of the choke input filter is to reduce severe peak charge currents.
Tube rectifiers can't take huge dc peak I.
High Idc peaks mean noise can get into earth rails and the signal.
Not if one uses careful layout and good parts though.
But usually L1 in a LCLC filter needs to be potted and well varnished to
ensure it is silent mechanically.

I rarely ever have used LCLC, el-cap values today are high, they are cheap,
and reliablity is superb, due to
their qualities being tailored for use in arduous SMPS conditions.

Concerns raised about power supplies below are covered in the above analysae.

Patrick Turner.



See above about efficiency and cost (cost at least in days of old --
maybe today a humongous choke could be cheaper).

Furthermore, the power supply is part of the transfer function. The
signal literally runs through it. In your mind's eye draw a line from
the bottom of the last filter cap on the T39
http://members.lycos.co.uk/fiultra/T...trafi-crct.jpg
to the ground of the RCA socket, and you will get the idea. In an SE
amp you want control over all the time constants, and therefore in the
power supply too. You can't just throw around extra capacitance without
considering the specification of available chokes, the time constants
you want further on, and so on, even onto your speakers (you can't
output too much below 32Hz in Lowthers, for instance, so you that is a
time constant in the 300B circuit which influences time constants all
the way back to the power supply). Again, this is an example of why
Patrick despairs of repair hacks who won't hit the RDH hard ever
learning anything really useful about tube amps. I mentioned Rankin
above for a purpose; he is a very thorough engineer and he says that
*after he had designed an amp* there were an additional 100 or so
checks he makes to be sure the thing will work right.

With all your prior losses, you are running well below the
saturation level of a single unit (400/575ma). 500V caps are cheap
these days, even 50uF or better, certainly cheaper than iron. And if
all you want to filter is 50/60Hz chop, one will do fine.

No, no, no! See above about time constants in the filters, efficiency
in the choke sections, etc. Then, as a practical matter, check a
catalogue for the physical size of the polyprop caps I have specified,
and you will be absolutely horrified at the floor space already on the
amp.

As a small
aside, the 5U4 rectifier is much cheaper, albeit not quite as rugged
and without the slow-start characteristics that distinguish the 5AR4.

I have a box full of 5U4 sitting three feet to my left as I write this.
If I wanted a 5U4, I would have specified and fitted it. Peter, put any
consideration of cost out of your mind unless and until *I* or another
*established* audiophile come to mention it; cost considerations
simply do not apply to DIY ultra-fi amps. The GZ34 is there because it
sounds right and, important this, to protect the 300B in DIY-built amps
with its slow-start filament. It is being replaced with GZ37, cost no
object, because that sounds better still.

But in any case, a single choke with sufficient capacitance would drop
any chop way below other noise sources.

No. RTRDH.

Are you familiar with Mad Man Muntz? He would go into his skunk-works
whenever his engineers decided they had a new product to develop, and
start cutting out parts (he was an excellent EE, so this was not done
at random) until whatever-it-was stopped working. *That* was the magic
point from which to design.

I question from the perspective of one who is usually presented with
smoking ruins and given the mandate to 'make it work'.

I have never had an amp fail to work on switch-on.

Many times
without benefit of schematics, or if they are available, facing so many
whimsical modifications to make the schematics of dubious value. So,
"expected" and "actual" values are important things to know.

The voltages and currents are on my circuit, together with the value
and rating of every other component, together with the maker's name of
every component, and in may cases the name of a supplier if the
component is rare. Again, you'd do better to study and discuss the T39
circuit.

At times,
I thank my lucky stars that this is a hobby.... so I do not have to
make a living at it. Otherwise, not 1 unit in 10 that I see would be
worth the time and trouble to fix.

I find it cheaper at the hourly rates my time is worth to design and
build a new amp rather than fix a broken one if much more than the fuse
is gone. It seems to me that amateur troubleshooting of high-voltage
devices is an ulcer-making pastime. Anyone who doesn't find it
ulcer-making lacks the imagination to be afraid of high voltage and
should find another hobby.

Peter Wieck
Wyncote, PA

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 wrote:

Patrick Turner wrote:
" wrote:

Why do you still have some 100 watts of dropping resistors on the
secondary side of the transformer?

http://members.lycos.co.uk/fiultra/t...17acircuit.jpg

Peter Wieck
Wyncote, PA

I cannot see any 100watt dropping resistors anywhere.
Do you mean the 2 x 100 ohm to ground the 417 heaters?

Which transformer do you mean? output or power?

Patrick Turner.

Witless Wiecky is looking at the circuit of a different amp, on an
already replaced version of the schematic -- but there aren't any 100W
resistors on there either.

Poor Witless thinks that if one uses a 50W resistor it will give off
50W of heat, regardless of how much current flows in it. It really is
frustrating trying to help him. Sander and John and I tried to explain
to him why:

1. Why one shouldn't use halfwave rectification.

Its inefficient.

But then as soon as silicon diodes became rugged enough McIntosh used them
in voltage doubler supplies where you effectively have two series caps each
charged as mains F only.
So a 120mA supply with halfwave Si diodes is actually doable, but does not
seem right.
Tghe effectiveness of chokes and caps is half though, since twice the
values must be used for the same attenuation
factors as used with fullwave.



2. Why a bleed resistor (he counts the bleeder in his list of "unwanted
heat dissipators") is necessary.

The bleeders are only needed to stop soaring B+ if there is no anode
current which is the case where
a PS is for a class B or class C amp.

In a class A amp the bleeders so little except make the PS safe if the PS
is turned on without the
output tubes plugged in which would cause B+ to soar to 1.4 x vrms of the
HT winding, thus perhaps blowing up all the electros.



3. Why a stiff bleed stabilizes the power delivery.

see above



4. Why ballasts are in the secondary legs of the power transformer.

trimming...



5. Why one doesn't lower voltage by inserting resistors into the
primary.

6. Why choke input power filters are made with two sections.

See my other post...



Etcetera, a very, very long list of things we take for granted that I
was amazed to discover even a repair hack doesn't know, and especially
a repair hack like Witless, who has the presumption to lecture us.

I have concluded that Witless Wiecky is obdurately and permanently
ignorant and a waste of my time. I've already put him back in my
killfile.

;



I really can't understand the sort of person who arrives on RAT without
any visible achievement --and starts telling the doers how they should
do a job they have been doing well for years. Doesn't it occur to
clowns like Witless Wiecky that they should read Morgan Jones and at
least a few relevant chapters of the RDH before they start preaching to
someone who has been designing amps for fifteen years? As far as I can
make out, Witless doesn't know the most basic things about electricity
or amplifers. Even as a repair hack his knowledge must be suspect if
he doesn't even understand the difference between DC and AC, which is
the implication of his suggestion of a diode on only one winding of a
power transformer secondary and the subsequent horrifying exchange with
John Byrns. The people who let Wiecky "clean" (his word; one presumes
he didn't attempt repair) their Conrad Johnson amps are either rich
enough to afford a new one when he wrecks it or reckless with their
property. Witless must be a danger to himself too; ignorance and high
voltage are fatal neighbours.

Well I hope ppl do learn something some time.....

and without getting upset.

Patrick Turner.



Andre Jute

This a superb post, Patrick, much more than I hoped for. I shall save
it for when I write the KISS chapter on power supply design.Thanks. --
Andre Jute


Patrick Turner wrote:


In your long post to put peter right, I come across this....


Two chokes? Why?

Because that is how one builds a choke input supply. It cannot be
wound/specified/built more economically (Patrick?) or efficiently in
terms of smoothing than as two (equal) sections.

The use of LCLC in a B+ power supply does offer the good smoothing.

The choke values and following C values of the LC circuits have to be chosen
carefully to avoid any undamped
resonances. In the case where you have 10H, 51uF, Fo = 7Hz, and for the
second LC with 10H and 100uF, Fo = 3.5Hz,
and both F are low enough.
The ac voltage at twice the mains F, say 100Hz, at the input to the choke1
from rectifiers = 0.67 x 400 = 268Vrms,
and L1 C1 has an attenuation factor of 31 / 6,280 = 0.0049, so at C1, Vripple
= 1.31Vrms.
The attenuation of L2 C2 = 16 / 6,280 = 0.0025 so ripple at C2 = 0.0032 Vrms,
quite low enough to not
inject much noise into the OPT because the output triode tube has low Ra, 800
ohms, and the load will maybe 5k, so nearly all the hum from the C2 is across
the OPT.

The use of 10H chokes to cope with 130mA is uneconomical when compared to
just using CLC, or even CRC,
where the value of C1 and C2 is 470uF x 450V rated caps with a 300 volt
winding for an SS bridge rectifier.
with about 320vrms for the HT you can afford to have 50 ohms at 20W rating to
limit high charge currents to the caps,
and the GZ34 is better used as a slow turn on diode, ahead of the R or L in
the CRC filter.

The circuit of the PS at
http://members.lycos.co.uk/fiultra/T...trafi-crct.jpg
has a traditional set up apart from having 1/2 the rectifiers in tube for
slow turn on and the other 1/2 in SS.

I am not against tradition should anyone want to be traditional.

Consider a CRC for say 120mA at 400V. There is no bleed current.

Regardless of the series R to limit peak charge currents into C, and
therefore reduce dissipation in the B+ winding,
Vripple at C1 470uF = 0.56 Vrms.

We want to get down to match the LCLC supply, ie, have Vr = 3mV.

So the attenuation factor must be 0.003 / 0.56 = 0.0053, say 0.005.

CRC requires that R *or* ZL = ZC / 0.005 = 3.4 / 0.005 where C = 470uF for
C2.

so R = 680 ohms, or L = 1.08H.

Now 120mA would give a V drop of 81V dc across the R, and so Vin at C1 would
have to be +480V,
and too high to be able to use a single 470 uf cap rated at 450V at C1.

But the choke would be fine. Fo for LC = & Hz, low enough, but any choke of
more than 1.5h will do.

But we could also employ CRCRC perhaps. If the total attenation factor needed
0.005,
then each RC section needs to have attenuation of the square root of 0.005 =
0.071,
so R needs to be 3.4 / 0.071 = 47 ohms, and dcV drop is only 5V.
We may use say a GZ34 plus 22 ohms for R1, and 47 ohms for R2, and we have a
decent
supply without any chokes, no bleed current, slow turn on, efficient use of
transformer, and no resonant LC behaviour.

if CRCRCRC was used, the requirement is that R 10 x ZC, so 39 ohms is
plenty, and attenuation factor
= 0.1 x 0.1 x 0.1 = 0.001, and ripple at C4 1mV.
The benefit with 470uF is that it is a mightly nice low Z anchor from which
the SE OPT is hooked up to.

If you insist on two chokes, then if C = 470 uF, then you are goverened by
resobance because if you had
ZL = say 100 ohms, or 63mH, then Fo = 29Hz, way too high.

Using say 2 to 3 Henrys with CLC is far cheaper than using x 10H chokes imho.

In my SEUL amp where Idc out = 220mA, I used CLC with C1 = 340uF, C2 = 235uF
and L = 9H, a monster
C cored choke, so Fo 5Hz, and all is well.

I have used GZ32 in reformed Quad II where it is a slow turn on series diode
with R = 90ohms when on
and where Idc = 130mA. But it isn't necessary because output tubes come on
slower than the GZ32, or 34,
and B+ soars a bit anyway. With 300B though, the cathode warms up quite fast,
and the slow turn on does give a
nice delay, but really it isn't a hiuge benefit.
The better thing is to have the output tubes sit there with heaters going to
2 minutes without any B+ so as to allow the
gas molecules to be absorbed by the gettering before the B+ is applied when
the gas becomes +ve charged ions which then bombard the cathode. That's the
theory anyway..

But then when the B+ does come on with hot cathodes, you tend to get an Idc
surge, but I doubt it causes any problems.
The large Cs will have the B+ rise fairly slowly anyway...

Chokes were used in older PS mainly because C values were hopelessly high
since electros were
temperamental. And the swinging choke was de-riguer for supplies to PP amps
working in mainly
class B ( or class C in transmitters ) because Idc varies with signal level
and CLC with tube rectifiers
caused attrocious variations in B+ with power levels.
The RDH4 graphs of regulation with LC filters ( with the optional second LC )
shows that the swinger choke is far better
than the same rectifier and output current range than CLC let alone CRC.

PP amps could get away without any more than one LC input filter because the
PP output stage tends to
reject the hum while working in class A, which they do for most of the music.

SE amps need both a quiet supply and a low impedance at the OPT connection.
regulation does not matter and in fact wwith plenty of series R then charge
up of the large caps involved is a peaceful process and if an output tube
shorts you want a cheap R to go open before a choke or OPT winding does.

So the R used for power supplies should not be too rugged, just rugged
enough.


There is more than one way to do it all, happy choking if you must, its
theraputic thay say....







The 5AR4 is a pretty good, quite rugged (if expensive)
rectifier.

So what? I'm specifying a couple of grand's worth of tubes already.
Anyway, it sounds better than semiconductor diodes and lasts longer too
unless you heatsink diode bridges properly.

In the T39 the GZ34 will be replaced with a GZ37, which will really
hurt if you worry about costs!

And it would seem simpler to add additional capacitance on
the line-side of the first choke, thereby eliminating the need for the
second?

The idea of the choke input filter is to reduce severe peak charge currents.
Tube rectifiers can't take huge dc peak I.
High Idc peaks mean noise can get into earth rails and the signal.
Not if one uses careful layout and good parts though.
But usually L1 in a LCLC filter needs to be potted and well varnished to
ensure it is silent mechanically.

I rarely ever have used LCLC, el-cap values today are high, they are cheap,
and reliablity is superb, due to
their qualities being tailored for use in arduous SMPS conditions.

Concerns raised about power supplies below are covered in the above analysae.

Patrick Turner.



See above about efficiency and cost (cost at least in days of old --
maybe today a humongous choke could be cheaper).

Furthermore, the power supply is part of the transfer function. The
signal literally runs through it. In your mind's eye draw a line from
the bottom of the last filter cap on the T39
http://members.lycos.co.uk/fiultra/T...trafi-crct.jpg
to the ground of the RCA socket, and you will get the idea. In an SE
amp you want control over all the time constants, and therefore in the
power supply too. You can't just throw around extra capacitance without
considering the specification of available chokes, the time constants
you want further on, and so on, even onto your speakers (you can't
output too much below 32Hz in Lowthers, for instance, so you that is a
time constant in the 300B circuit which influences time constants all
the way back to the power supply). Again, this is an example of why
Patrick despairs of repair hacks who won't hit the RDH hard ever
learning anything really useful about tube amps. I mentioned Rankin
above for a purpose; he is a very thorough engineer and he says that
*after he had designed an amp* there were an additional 100 or so
checks he makes to be sure the thing will work right.

With all your prior losses, you are running well below the
saturation level of a single unit (400/575ma). 500V caps are cheap
these days, even 50uF or better, certainly cheaper than iron. And if
all you want to filter is 50/60Hz chop, one will do fine.

No, no, no! See above about time constants in the filters, efficiency
in the choke sections, etc. Then, as a practical matter, check a
catalogue for the physical size of the polyprop caps I have specified,
and you will be absolutely horrified at the floor space already on the
amp.

As a small
aside, the 5U4 rectifier is much cheaper, albeit not quite as rugged
and without the slow-start characteristics that distinguish the 5AR4.

I have a box full of 5U4 sitting three feet to my left as I write this.
If I wanted a 5U4, I would have specified and fitted it. Peter, put any
consideration of cost out of your mind unless and until *I* or another
*established* audiophile come to mention it; cost considerations
simply do not apply to DIY ultra-fi amps. The GZ34 is there because it
sounds right and, important this, to protect the 300B in DIY-built amps
with its slow-start filament. It is being replaced with GZ37, cost no
object, because that sounds better still.

But in any case, a single choke with sufficient capacitance would drop
any chop way below other noise sources.

No. RTRDH.

Are you familiar with Mad Man Muntz? He would go into his skunk-works
whenever his engineers decided they had a new product to develop, and
start cutting out parts (he was an excellent EE, so this was not done
at random) until whatever-it-was stopped working. *That* was the magic
point from which to design.

I question from the perspective of one who is usually presented with
smoking ruins and given the mandate to 'make it work'.

I have never had an amp fail to work on switch-on.

Many times
without benefit of schematics, or if they are available, facing so many
whimsical modifications to make the schematics of dubious value. So,
"expected" and "actual" values are important things to know.

The voltages and currents are on my circuit, together with the value
and rating of every other component, together with the maker's name of
every component, and in may cases the name of a supplier if the
component is rare. Again, you'd do better to study and discuss the T39
circuit.

At times,
I thank my lucky stars that this is a hobby.... so I do not have to
make a living at it. Otherwise, not 1 unit in 10 that I see would be
worth the time and trouble to fix.

I find it cheaper at the hourly rates my time is worth to design and
build a new amp rather than fix a broken one if much more than the fuse
is gone. It seems to me that amateur troubleshooting of high-voltage
devices is an ulcer-making pastime. Anyone who doesn't find it
ulcer-making lacks the imagination to be afraid of high voltage and
should find another hobby.

Peter Wieck
Wyncote, PA

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" wrote in message ups.com...
This a superb post, Patrick, much more than I hoped for. I shall save
it for when I write the KISS chapter on power supply design.Thanks. --
Andre Jute

You're a fraud, Andre. Patrick is perfectly capable of publishing this
material in his own website. No good purpose is served by your
plagiarizing it.

-Henry

In article . com,
" wrote:

John:

OK. So, what you are writing is that clipping off half the sine wave
will have no effect on the secondary voltage, or it will drop it to
zero, depending on the orientation of the diode? This due to the nature
of the rectifier used?

Hi Peter,

Perhaps your description of what it is you are proposing was to vague for
me to understand. What I thought you were talking about was replacing one
of the ballast resistors with a 1N4007 diode, it wasn't clear to me what
you would do with the second of the two ballast resistors?

Ignoring the problem of the second 5AR4 rectifier plate for now, if you
replace the ballast resistor with a 1N4007 diode connected between the end
of the transformer HV winding and one rectifier plate, the impact on the
output voltage will be virtually nil. This assumes that you connect the
cathode of the diode to the anode of the 5AR4, in which case the added
diode will simply be "clipping off half the sine wave", the same half that
half, that the 5AR4 was already clipping off, hence no change in output.
The result is problematic if you put the diode in the other way around
because there will be no conduction through 5AR4 on one half cycle,
converting the circuit to half wave rectification which will unleash all
sorts of havoc with the choke input filter used in this design. The
circuit could be converted to half wave operation by connecting one of the
two 5AR4 plates to ground to provide a current path for the choke input
filter on the alternate half cycles. This would reduce the voltage by a
factor of approximately 0.5 with the choke input filter, unfortunately a
factor of 0.5 is not useful in this instance.

It is worth noting that the power dissipation in each of the two 330 Ohm
ballast resistors is only about 1 Watt under the simplifying assumption
that the input choke has infinite inductance. Of course in reality the
inductance of the choke is finite and the actual power dissipation will be
greater, but it won't be anywhere close to the 100 Watts that has been
bandied about.

And apart from that, have you found an application other than the one
in question where such 'ballast' resistors are used? That is, apart
from home-brew necessities adapting not-quite-suited parts to a
particular purpose?

The use of separate ballast resistors is not common, the required
impedance is usually provided by the winding resistance and sometimes the
leakage inductance of the power transformer. Why pay for separate
resistors when you can save a few pennies by simply having your power
transformer wound with thinner wire to provide the necessary resistance?
I have actually seen ballast resistors used in a few amplifiers, although
it was so long ago that I can't cite any model numbers. I believe it was
in pro equipment that I observed the use of ballast resistors. I can
imagine two reasons why this might have been done. One reason would be to
allow the use of an existing transformer, originally designed for a
different rectifier, in a limited production piece of equipment that
didn't justify the specification of a new transformer design, or where it
was desired to hold only one transformer in stock for replacement
purposes. The second possible reason is that the high resistance
transformer windings would add heat to the transformer, reducing the
reliability of the equipment. By using separate ballast resistors the
heat can be dissipated in a more benign way, adding to the longevity of
the transformer.

If you doubt the wisdom of using some sort of ballast resistance I suggest
you check your valve data book where you will find specifications for the
minimum impedance that must be connected to each rectifier plate in order
to avoid disaster with capacitor input filters. Of course in the case at
hand a choke input filter is being used, so ballast resistors aren't
actually necessary. However as Andre has already explained, the amplifier
in question is simply the driver stage of a larger amplifier and the power
supply was designed for the complete amplifier, so when Andre wanted to
try the driver stage as an amplifier on its own, he needed to add the
ballast resistors to drop the voltage back to normal. Of course he could
have simply added a large enough bleeder resistor to soak up the current
normally consumed by the output stage, but then the power dissipation
would begin approaching the 100 Watts that has been mentioned.

I should mention that I haven't looked at the schematics for the complete
amplifier, since my interest is only in the "potato" version, so my
assumptions could be wrong and there could be some holes in my supposition
as to why Andre used the ballast resistors.

If you would try designing something yourself you would begin to get a
feel for some of the tradeoffs involved.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

John Byrns wrote:
In article . com,
" wrote:

John:

OK. So, what you are writing is that clipping off half the sine wave
will have no effect on the secondary voltage, or it will drop it to
zero, depending on the orientation of the diode? This due to the nature
of the rectifier used?

Hi Peter,

Perhaps your description of what it is you are proposing was to vague for
me to understand. What I thought you were talking about was replacing one
of the ballast resistors with a 1N4007 diode, it wasn't clear to me what
you would do with the second of the two ballast resistors?

Ignoring the problem of the second 5AR4 rectifier plate for now, if you
replace the ballast resistor with a 1N4007 diode connected between the end
of the transformer HV winding and one rectifier plate, the impact on the
output voltage will be virtually nil. This assumes that you connect the
cathode of the diode to the anode of the 5AR4, in which case the added
diode will simply be "clipping off half the sine wave", the same half that
half, that the 5AR4 was already clipping off, hence no change in output.
The result is problematic if you put the diode in the other way around
because there will be no conduction through 5AR4 on one half cycle,
converting the circuit to half wave rectification which will unleash all
sorts of havoc with the choke input filter used in this design. The
circuit could be converted to half wave operation by connecting one of the
two 5AR4 plates to ground to provide a current path for the choke input
filter on the alternate half cycles. This would reduce the voltage by a
factor of approximately 0.5 with the choke input filter, unfortunately a
factor of 0.5 is not useful in this instance.

That's like cutting off your nose to spite your face, even aside from
the difficulties of a half-wave rectified power supply with a choke
input filter, in a hi-fi amp, in a SET with its constant current
demand, in a semi-traditional design with relatively low capicitance.

It is worth noting that the power dissipation in each of the two 330 Ohm
ballast resistors is only about 1 Watt under the simplifying assumption
that the input choke has infinite inductance. Of course in reality the
inductance of the choke is finite and the actual power dissipation will be
greater, but it won't be anywhere close to the 100 Watts that has been
bandied about.

Wiecky arrived at his 100W by erroneously assuming that a resistor
constantly dissipates its whole power rating, i.e. that a 50W resistor
gives off 50W of heat regardless of its ohmage or the current flowing
through it. How do you begin to educate such ignorance? Then he added
up all the big resistances he could see, including the bleed which (in
addition to the other reasons Sander and Patrick and I have already
covered) is essential for the personal safety of the builder, owner and
user of a DIY amp. I will not countenance a tube amp without a bleeder,
not with caps charged up to several hundreds of volts.

And apart from that, have you found an application other than the one
in question where such 'ballast' resistors are used? That is, apart
from home-brew necessities adapting not-quite-suited parts to a
particular purpose?

The use of separate ballast resistors is not common, the required
impedance is usually provided by the winding resistance and sometimes the
leakage inductance of the power transformer. Why pay for separate
resistors when you can save a few pennies by simply having your power
transformer wound with thinner wire to provide the necessary resistance?
I have actually seen ballast resistors used in a few amplifiers, although
it was so long ago that I can't cite any model numbers. I believe it was
in pro equipment that I observed the use of ballast resistors. I can
imagine two reasons why this might have been done. One reason would be to
allow the use of an existing transformer, originally designed for a
different rectifier, in a limited production piece of equipment that
didn't justify the specification of a new transformer design, or where it
was desired to hold only one transformer in stock for replacement
purposes. The second possible reason is that the high resistance
transformer windings would add heat to the transformer, reducing the
reliability of the equipment. By using separate ballast resistors the
heat can be dissipated in a more benign way, adding to the longevity of
the transformer.

If you doubt the wisdom of using some sort of ballast resistance I suggest
you check your valve data book where you will find specifications for the
minimum impedance that must be connected to each rectifier plate in order
to avoid disaster with capacitor input filters. Of course in the case at
hand a choke input filter is being used, so ballast resistors aren't
actually necessary. However as Andre has already explained, the amplifier
in question is simply the driver stage of a larger amplifier and the power
supply was designed for the complete amplifier, so when Andre wanted to
try the driver stage as an amplifier on its own, he needed to add the
ballast resistors to drop the voltage back to normal. Of course he could
have simply added a large enough bleeder resistor to soak up the current
normally consumed by the output stage, but then the power dissipation
would begin approaching the 100 Watts that has been mentioned.

I calculated this possibility, according my scratchsheet, still on my
workbench clipboard. 110mA or thereabouts might have done the job, but
it would have meant a 1600 ohm resistor dissipating at least 20W under
the best conditions, meaning the requirement for a huge, expensive and
really unnecessary 100W resistor. Any bleed, never mind one this
critical, really needs a safety multiple of at least 3. Suddenly we
jump from a few watts of heat inside the amp from those ballasts to
20W! That's going backwards! And all because Witless Wiecky's mum was
frightened by a production cost-accountant while she carried him.

I should mention that I haven't looked at the schematics for the complete
amplifier, since my interest is only in the "potato" version, so my
assumptions could be wrong and there could be some holes in my supposition
as to why Andre used the ballast resistors.

Spot on, John. I might just add that I automatically added ballast
resistors to the circuit for the real amp, here,
http://members.lycos.co.uk/fiultra/T...trafi-crct.jpg
because I always use ballasts when I can, and had to remove them
because they sucked up too much voltage. I firmly believe those
ballasts add to that margin of power stabilization which in turn adds
to the silence of the amp which give this amp its livability, that edge
of possibly subliminal superiority. Nothing clever, just attention to
every small thing; it adds up.

If you would try designing something yourself you would begin to get a
feel for some of the tradeoffs involved.

Past time.

Regards,

John Byrns

Surf my web pages at, http://users.rcn.com/jbyrns/

Andre Jute

Henry Pasternack wrote:

"Andre Jute" wrote in message ups.com...
This a superb post, Patrick, much more than I hoped for. I shall save
it for when I write the KISS chapter on power supply design.Thanks. --
Andre Jute

You're a fraud, Andre. Patrick is perfectly capable of publishing this
material in his own website. No good purpose is served by your
plagiarizing it.

-Henry

If anything is doable with some simple application of basic LCR filter theory, it power supplies.

Rather than have an argy bargy over trifling issues, I have avoided worrying much about copyright.

My information is usable by anyone, and i would prefer to simply see people quote me if they adopt
what they see as good advice, that's all.

When the 4th edition of my website is finished, there will be a lot more info pumped into the public domain.

For example, I am giving all the details of my latest phono stage amp with a cascode fet + triode input stage
within.
I got the basic idea from Allen Wright, and i wouldn't dream of mentioning my circuit workings without
reference to his original ideas in his FVP of 1988.
I think I explain how his idea works better than he did in his Preamp Cookbook.

If people want to include the knowledge as their own, they should aknowledge where they have learned, that
is all i ask. Much of what i am compiling is simple applied ideas from the past and which everyone should be
aware of anyway.

I am presently up to about 12MB with the 4th edition. There will be a lot more graphs and schematics, many of
which
are done more neatly in MS Paint to make a monochrome image and to be posted as a GIF
so that what was 200kB for a large complex amp and power supply schematic will be 20kB but more readable
and printable to an A4 page per screen full.
As fast as I reduce the schematics and graph sizes, I seem to be making up reams of text, and its a job to edit,
edit, edit, and edit again to make sure each word isn't wasted and the nit pickers don't have a field day.

I have lost count of the hours i am spending.

I shouldn't ask if you are building some project now should I?

Patrick Turner.

But, nah, I used to work in the theatre and in films and I still do the odd thing in television,

Finally, something that we can believe.

Still have calouses from pushing that broom, Mr. McCoy? Getting spilled
soda off the floors can be a real PITA?

Peter Wieck
Wyncote, PA

"Patrick Turner" wrote in message ...
I shouldn't ask if you are building some project now should I?

All right, Patrick, I'll take the bait.

Because of the demands of work, family, and home maintenance, I have
little time for hobbies these days. I've had to learn to be a carpenter after
trying unsuccessfully to find a reliable contractor to do some restoration
on my house at a reasonable price. Most of my remaining free time is
taken up with piano practice.

I have a pile of tiny surface mount parts sitting on the bench waiting to
turn into an RF vector network analyzer. And after that gets done, I
want to use it to work on my solid-state communications receiver
project. I don't imagine anyone here would be that interested in all that.

Piano is so demanding yet rewarding that it pretty much takes top
priority in the leisure time category these days.

I do have an audio project I need to build, and that is to make a phono
preamp. One circuit I've been considering is Allen Wright's FVP. I
would be curious to hear your thoughts on this design. A comparable
design, without the FET, is Steve Bench's RIAA5. If you have any
comment on that circuit, I'd like to hear about it as well.

I'd even go so far as to say, in order to motivate myself, that if you can
help me settle on a circuit, I promise to build it up and post the results
here.

-Henry

"Andre Jute" wrote in message ups.com...
The point of a swinging choke is to provide a fractional delay while
capacitors charge up. The slow heater on the GZ34 already provides
a delay. Furthermore, a hefty bleed loads the choke even with an
instantly-on rectifier so that there is also an instant demand for
current. All these matters tend to reduce the need for a swinging
choke, which today is a very rare item.

As usual, you have taken a few valid facts and hopelessly confused
them, coming to a well-known conclusion based on incomprehensible
and largely erroneous reasoning.

The point of a swinging choke is not to provide a fractional delay
while the capacitors charge up. A swinging choke is used to allow
a physically small inductor in a choke-input power supply without
the power wasted by an aggressive bleed resistor. Because the
swinging choke has quite high inductance at low currents, a light
bleed current can be used without danger of the B+ surging.

The reason the rectifier tube warm-up time is relevant is that if the
rectifier warms up more slowly than the signal tubes, the voltage
surge cannot occur. It's very, very risky to rely on this delay to
protect the power supply. If there is ever a heater failure, the signal
tubes may never warm up . With no current drawn by a cold circuit,
and with insufficient bleed current, the power supply capacitors will
charge to about 150% of their normal operating voltage, possibly
causing them to explode.

It is always a good idea when using a choke-input filter to specify
capacitors able to withstand the full 1.414 * VRMS voltage in the
event that both the signal circuitry and the bleeder resistor fail.

The time it takes the capacitors to charge up is related to other
important aspects of power supply design, but is essentially
irrelevant to this question.

The reason swinging chokes are so rare nowadays is that the
availability of cheap silicon rectifiers and large electrolytic capacitors
makes capacitor-input filters more economical to build than choke-
input filters. Therefore, most filter chokes produced today are
intended for smoothing, not choke-input service. Also, as amateurs,
we aren't that concerned about saving space and weight, so there is
little demand in the hobbyist market for swinging chokes.

I am sure this information is reprinted in many other places. My
main purpose in posting it now is to highlight your incompetence.

-Henry

Henry:

Just ignore Mr. McCoy. He is no technician certainly and his design
credentials are well-established.

Just be satisfied that the discussions around his errors and omissions
are far more useful and informative than the actual basis for said
discussions. If he were to have deliberately set out to show "what not
to do" when designing an amplifier (especially one around his purported
$1000 worth of tubes), he could have done no better.

Attempting to have an intelligent or useful or informative discussion
with him is the functional equivalent of ****ing up a rope... the
backwash is not worth the effort and the attempt was dubious initially.
He will _never_ admit that any choice(s) he has made or might make are
anything other than the _only_ possible choice... when confronted with
invincible ignorance the best option is to accept that the purveyor of
same will never change. All else that may be done is to prevent others
from being sucked into the same mistakes... and there are many of those
to be sure.

We are dealing here with revealed religion. All things that are in any
way vague or contrary to common sense are mysteries of the Faith and to
be taken on faith. What is so sad is that Mr. McCoy has taken it on to
the next step and made his little electronic abortion into a Cult
Object... and would have his adherents (but certainly not himself)
drink Magic Kool-Aid rather than admit fault in it, his assumptions or
himself.

Peter Wieck
Wyncote, PA

On Tue, 4 Apr 2006 14:24:22 -0400, "Henry Pasternack"
wrote:

I have a pile of tiny surface mount parts sitting on the bench waiting to
turn into an RF vector network analyzer. And after that gets done, I
want to use it to work on my solid-state communications receiver
project. I don't imagine anyone here would be that interested in all that.

I'd be interested in knowing what an RF vector network
analyzer *was*. Been too far outa the loop lately, obviously.


I do have an audio project I need to build, and that is to make a phono
preamp. One circuit I've been considering is Allen Wright's FVP. I
would be curious to hear your thoughts on this design. A comparable
design, without the FET, is Steve Bench's RIAA5. If you have any
comment on that circuit, I'd like to hear about it as well.

I'd even go so far as to say, in order to motivate myself, that if you can
help me settle on a circuit, I promise to build it up and post the results
here.

I'm also building a new phono equalizer. I'm leaning toward
a long-loop design, but could be convinced to bring the
feedback point from the output of the second voltage gain
stage rather than from the output of the followers.

Topology is complementary all the way; diff-JFET first stage;
unique second stage with complementary JFETs with sources
floating but connected together by a small bias resistor;
junction of output drains feeding followers and (possibly)
EQ feedback network; other drains to power supply rails.
(Diff-in, single-ended out; cool, eh? How come I'm not rich?)
The usual DC servo's, etc. Nakamichi type power supply ground
decoupling. Yada, yada.

I'd be very interested in any comments, results, etc. in your
exploration.

Thanks, as always,

Chris Hornbeck

Henry Pasternack wrote:

"Patrick Turner" wrote in message ...
I shouldn't ask if you are building some project now should I?

All right, Patrick, I'll take the bait.

Because of the demands of work, family, and home maintenance, I have
little time for hobbies these days. I've had to learn to be a carpenter after
trying unsuccessfully to find a reliable contractor to do some restoration
on my house at a reasonable price. Most of my remaining free time is
taken up with piano practice.

It so good to hear that someone other than myself and Jesus Christ didn't think it too bad to be a
capenter in a former life......



I have a pile of tiny surface mount parts sitting on the bench waiting to
turn into an RF vector network analyzer. And after that gets done, I
want to use it to work on my solid-state communications receiver
project. I don't imagine anyone here would be that interested in all that.

Er, have ye not heard that simply digizing the antenna signal and counting out the wanted audio signal
with computerational techiques is where it's at? Maybe I'm wrong.

Heck, I rather built a tubed HF radio; I have several I want to restore, but I never have the time to
explore bands
above the audio band....



Piano is so demanding yet rewarding that it pretty much takes top
priority in the leisure time category these days.

I heard Beethoven's piano concerto in Cminor on the way home from a concert at the local School of Music.

I can't live without REAL music..... At the concert a girl played a chello for awhile to accompaying piano;
tears streamed down my face, whatever the composer had in mind hit its intended target......



I do have an audio project I need to build, and that is to make a phono
preamp. One circuit I've been considering is Allen Wright's FVP. I
would be curious to hear your thoughts on this design.

The FVP was a landmark design because he was I think the first to combine the best attribututes of a high gm

j-fet such as the 2SK369 or 2SK147 ( very low input noise, triode like THD, compatibility in a cathode
circuit, )
with the best attributes of a triode ( musicality, dynamic range, low THD etc,)

A comparable
design, without the FET, is Steve Bench's RIAA5. If you have any
comment on that circuit, I'd like to hear about it as well.

The FVP has NFB RIAA correction. To most serious ppl's ears with good systems
RIAA eq is better achieved 'passively'.

In my next edition of my website which I am now concluding I will have all the details and schematics of my
latest phono stage which does the business better than anything else I have come across.



I'd even go so far as to say, in order to motivate myself, that if you can
help me settle on a circuit, I promise to build it up and post the results
here.

I'll send you the schematic of the amp, and if you like the look of it, I can send you the other 4 sheets.
In each channel it uses one 2SK369, 1 x 6DJ8, 1 x 12AT7, 1 x 6CG7.
These are paralleled so each tube socket has just one triode each.

The circuit can be slightly modded to take many other types of tubes such as 12AY7 or 6SL7 for the
second and main gain stage, 6SN7 for the bootstrapped follower in lieu of 6CG7, etc.

Patrick Turner.





-Henry

Henry Pasternack wrote:

"Andre Jute" wrote in message ups.com...
The point of a swinging choke is to provide a fractional delay while
capacitors charge up. The slow heater on the GZ34 already provides
a delay. Furthermore, a hefty bleed loads the choke even with an
instantly-on rectifier so that there is also an instant demand for
current. All these matters tend to reduce the need for a swinging
choke, which today is a very rare item.

As usual, you have taken a few valid facts and hopelessly confused
them, coming to a well-known conclusion based on incomprehensible
and largely erroneous reasoning.

The point of a swinging choke is not to provide a fractional delay
while the capacitors charge up.

The "fractional" delay does not occur if silicon diodes are used; the choke saturates for a few cycles and
C is immediately charged up until vdc = 0.63 x peak voltage of the HT winding, or when Edc = 0.89 x Vrms of the
ac winding.


A swinging choke is used to allow
a physically small inductor in a choke-input power supply without
the power wasted by an aggressive bleed resistor. Because the
swinging choke has quite high inductance at low currents, a light
bleed current can be used without danger of the B+ surging.

Usually the bleed current is designed to be 10% of the maximum supply current. The bleed current could be the
idle current of the tubes, but until tube warm up occurs, a bleed current is needed so the bleed R is included
and when tubes start working some small extra loss is inclusive.

The choke is designed so L = RL / 1,100 where RL is the highest value, ie, when the bleeder current is the only
load.
So this allows a lower value of L rather than if we designed for bleed current = say 5% of total max current.
With a lower than higher value L its easier to then get the choke to swing a bit, so that when the RL is 1/10
of the bleeder value because dc flow into the class B / C output stage has increased 10 times during
high power output.




The reason the rectifier tube warm-up time is relevant is that if the
rectifier warms up more slowly than the signal tubes, the voltage
surge cannot occur. It's very, very risky to rely on this delay to
protect the power supply. If there is ever a heater failure, the signal
tubes may never warm up . With no current drawn by a cold circuit,
and with insufficient bleed current, the power supply capacitors will
charge to about 150% of their normal operating voltage, possibly
causing them to explode.

It is always a good idea when using a choke-input filter to specify
capacitors able to withstand the full 1.414 * VRMS voltage in the
event that both the signal circuitry and the bleeder resistor fail.

Its easy to use 350V rated caps in series for a supply that normally operates at +450V.
I do this even without a choke input filter. Caps are cheap.



The time it takes the capacitors to charge up is related to other
important aspects of power supply design, but is essentially
irrelevant to this question.

The reason swinging chokes are so rare nowadays is that the
availability of cheap silicon rectifiers and large electrolytic capacitors
makes capacitor-input filters more economical to build than choke-
input filters.

Well, Si diodes and high value cap input filters are better regulated than any tubed choke input filter.
Gone is the series resistance of choke and tube.
The choke input allowed the tube rectifier to conduct throughout the cycle; there is no peak charging
that had limits with tubes.

Therefore, most filter chokes produced today are
intended for smoothing, not choke-input service. Also, as amateurs,
we aren't that concerned about saving space and weight, so there is
little demand in the hobbyist market for swinging chokes.

Well if the choke is simply able to comply with RL / 1,100 where RL is the Edc / Idc and Idc is considered
at 10% of that normally drawn, the choke is probably ok for choke input with a higher V ac HT winding
to produce the same B+.

I have built a stereo 2 x 300 watt solid state amp supply with choke input filters using about 250mH chokes
that had 0.5 ohms winding resistance. These well gapped chokes were potted in steel cases
each about 100mm for each dimension; big, heavy, but effective. For good regulation with choke input, Dcr 5% of
RL at maximum dc draw. This usually makes the choke larger than if the same L value were used in a class A design
where a bit of dcr doesn't matter, since there is no need for good supply regulation; the Idc is constant.



I am sure this information is reprinted in many other places. My
main purpose in posting it now is to highlight your incompetence.

Nobody is perfectly competent. I do not post with purpose to point out mainly the incompetence of others,
but more to offer an alternative which may or may not appear to be truer than what else may have been said, or to
augment what has been said already.
I found teachers who came at me to primarily kick my butt of ignorance to be rude.
I'd rather they engage my sense of wonderment, and lead me to my own discovery of my misconceptions.
I would feel i wanted to shout them a beer, rather than run them over in the street.

Wonderment leads to hatchet burying. ( they say there are lots of worn out spades in Ireland,
lots of buried rusty hatchets, but also a shirtload of wonderment ).


RDH has a lot to say about chokes that i have not included, and should anyone follow what Hanna
said about chokes they'd be doing themselves a favour about choking knowledge.

Choke inputs are still used in many industrial applications.

Patrick Turner.



-Henry

"Mike Gilmour" wrote in message
...
:
: "Don Pearce" wrote in message
: ...
: On Sat, 1 Apr 2006 15:37:27 +0300, "Iain Churches"
: wrote:
:
:
:
: For musical testing I favour Bartok quartets - get a nicely staged
: recording and you will find both physical and tonal space between all
: the instruments that will reveal the actual quality of the system.
:
: For small ensemble, you cannot beat the Shostakovich Quartets.
: For something small and dynamic my show reel contains Stravinski:
: The Soldier's Tale. Then you need something to thunder, and not too
: modestly (:-)) Mussogrsky is the man for that. Pictures as an Exhibition
: (orchestration by Ravel) is most revealing.
:
: They would all do nicely.
:
: For system testing I use speech, from friends - both male and female.
: That is a really severe test, and very few systems actually sound like
: my friends.
:
: Hmm. Interesting idea:-) Two flaws. Few people have the equipment
: to record a voice with accuracy (a Tandberg will not do:-) to make it
: suitable for any kind of evaluation. Secondly, so few people are used
: to hearing the sound of there own voice that the speaker him/herself
: cannot take part in the evaluation.
:
:
: But not for me - I do have the equipment. And of course I would never
: use the sound of my own voice - I have no idea what I sound like to
: that degree of accuracy.
:
: d
:
: Pearce Consulting
: http://www.pearce.uk.com
:
:
: I agree, the human voice is an excellent test and I have the recording
: equipment also. The Organ Symphony & 1812 etc are also valid, I've recorded
: Carol Kidd (with permission) that was also a good test...
:
: Mike
:

yah, yah, if'you're all fishing for RAT thread of the month here,
forget it !
the mailing costs would 'kill' me :-)

err
say, maybe Stewart can send along some power BJT's ?
from the -will not ever be used, anyway- bin ...
to those for whom the smell of solder is
not
a lingering memory

Rudy

"Patrick Turner" wrote in message ...
Well, Si diodes and high value cap input filters are better regulated than any
tubed choke input filter. Gone is the series resistance of choke and tube.
The choke input allowed the tube rectifier to conduct throughout the cycle;
there is no peak charging that had limits with tubes.

It seems to be a strong concensus among subjective-minded hobbyists that
choke-input filters sound better because a lot less RF hash is generated by
diode switching. Even Morgan Jones, who's a pretty no-nonsense guy and
not at all afraid of silicon, thinks so. The argument makes sense to me.

This doesn't mean, though, that a given amplifier built with a cap-input
power supply will sound bad. There are many counter-examples.

Well if the choke is simply able to comply with RL / 1,100 where RL is
the Edc / Idc and Idc is considered at 10% of that normally drawn, the
choke is probably ok for choke input with a higher V ac HT winding
to produce the same B+.

There are a couple of concerns. The first is that the choke should have a
high enough current rating that it won't saturate with the large AC currents
flowing through it in this application. Manufacturers don't spec their chokes
for choke-input service and don't publish detailed design information, so
you have to make educated guesses.

The second concern is that the choke has to be made well enough that it
can withstand the added stress due to magnetostriction and core heating.
Hammond, which is the biggest supplier of affordable chokes in North
America, specifically states that their chokes are not rated for use in
choke-input filters. I don't know exactly what they mean by this. I have
a pair of Hammond 10H @ 300mA, 60 Ohm, chokes that run absolutely
cool and quiet as input chokes with a 1000VCT power transformer and
200mA DC load current.

Nobody is perfectly competent. I do not post with purpose to point out
mainly the incompetence of others, but more to offer an alternative which
may or may not appear to be truer than what else may have been said, or
to augment what has been said already.
I found teachers who came at me to primarily kick my butt of ignorance
to be rude.

Sometimes there is no choice but to kick the ass of a disruptive student.

-Henry

Sometimes there is no choice but to kick the ass of a disruptive student.

"Student" implies a willingness to learn.

That term is not applicable to Mr. McCoy.

Peter Wieck
Wyncote, PA

"Patrick Turner" wrote in message ...
Er, have ye not heard that simply digizing the antenna signal and counting
out the wanted audio signal with computerational techiques is where it's at?
Maybe I'm wrong.

I don't know much about that. A lot of amateurs are building direct-conversion
receivers with quadrature detectors and using DSPs for demodulation. Another
approach, perhaps capable of higher performance, is to use basically a regular
single-conversion front end but set the BFO to mix to an audio frequency second
IF (like 15kHz) and then do the final quadrature mixing to baseband, plus
detection, in DSP. There are excellent hobby projects out on the web for those
who are interested in that kind of thing.

The FVP has NFB RIAA correction. To most serious ppl's ears with good
systems RIAA eq is better achieved 'passively'.

Allen's designs haven't had any global feedback for years. He has some older
(but not as old as the ones you must have been looking at) schematics posted
on his website. You might want to have a look.

I'll send you the schematic of the amp, and if you like the look of it, I can
send you the other 4 sheets. In each channel it uses one 2SK369, 1 x 6DJ8,
1 x 12AT7, 1 x 6CG7. These are paralleled so each tube socket has just
one triode each.

I'd be curious to see it, although I was thinking of building something a bit
simpler.

Patrick Turner.

Thanks.

-Henry

wrote in message ups.com...
Sometimes there is no choice but to kick the ass of a disruptive student.

"Student" implies a willingness to learn.

That term is not applicable to Mr. McCoy.

I'll concede the point.

-Henry

"Henry Pasternack" said:


I have a pile of tiny surface mount parts sitting on the bench waiting to
turn into an RF vector network analyzer. And after that gets done, I
want to use it to work on my solid-state communications receiver
project. I don't imagine anyone here would be that interested in all that.

Piano is so demanding yet rewarding that it pretty much takes top
priority in the leisure time category these days.

I do have an audio project I need to build, and that is to make a phono
preamp. One circuit I've been considering is Allen Wright's FVP. I
would be curious to hear your thoughts on this design. A comparable
design, without the FET, is Steve Bench's RIAA5. If you have any
comment on that circuit, I'd like to hear about it as well.


At the moment, I'm working on a SMT circuit of a RIAA preamplifier,
that has to fit in the tonearm and/or shell.

I use 0603 size comonents, which are about the smallest size one can
still work with IMO.
I use M5238FP opamps from Mitsubishi, with phantom power supply via
the arm leads.
It is a classic opamp circuit with the RIAA correction in the feedback
loop.
Datasheet of the opamp:
http://www.ortodoxism.ro/datasheets/...on/mXrxqrq.pdf

Maybe this is something for you to try as well, since you mention
having SMT devices lying around in your post?

Another option is just the low correction and impedance concerion in
the shell or arm, and treble correction in the plinth.
I'll have to see how much mass will be added to the shell by the
circuit to determine which approach is best for me.

Excuse me for this silicon intermezzo, guys ;-)

--

- Never argue with idiots, they drag you down their level and beat you with experience. -

In article , "Henry Pasternack"
wrote:


Hi Henry,

This question is not meant as criticism of your general comments on
"swinging chokes". Are you sure that it is true that "The reason swinging
chokes are so rare nowadays is that the availability of cheap silicon
rectifiers and large electrolytic capacitors makes capacitor-input filters
more economical to build than choke- input filters"? My observation is
that chokes of any sort, "swinging" or filter, were gone from Hi-Fi amps
even before the use of silicon rectifiers became common, and also long
before large electrolytic capacitors came on the scene, which appear to
have come later than silicon rectifiers.


Regards,

John Byrns


The point of a swinging choke is not to provide a fractional delay
while the capacitors charge up. A swinging choke is used to allow
a physically small inductor in a choke-input power supply without
the power wasted by an aggressive bleed resistor. Because the
swinging choke has quite high inductance at low currents, a light
bleed current can be used without danger of the B+ surging.

The reason the rectifier tube warm-up time is relevant is that if the
rectifier warms up more slowly than the signal tubes, the voltage
surge cannot occur. It's very, very risky to rely on this delay to
protect the power supply. If there is ever a heater failure, the signal
tubes may never warm up . With no current drawn by a cold circuit,
and with insufficient bleed current, the power supply capacitors will
charge to about 150% of their normal operating voltage, possibly
causing them to explode.

It is always a good idea when using a choke-input filter to specify
capacitors able to withstand the full 1.414 * VRMS voltage in the
event that both the signal circuitry and the bleeder resistor fail.

The time it takes the capacitors to charge up is related to other
important aspects of power supply design, but is essentially
irrelevant to this question.

The reason swinging chokes are so rare nowadays is that the
availability of cheap silicon rectifiers and large electrolytic capacitors
makes capacitor-input filters more economical to build than choke-
input filters. Therefore, most filter chokes produced today are
intended for smoothing, not choke-input service. Also, as amateurs,
we aren't that concerned about saving space and weight, so there is
little demand in the hobbyist market for swinging chokes.

I am sure this information is reprinted in many other places. My
main purpose in posting it now is to highlight your incompetence.

-Henry


Surf my web pages at, http://users.rcn.com/jbyrns/

In article .com,
" wrote:

Henry:

Just ignore Mr. McCoy. He is no technician certainly and his design
credentials are well-established.

Peter,

You are jumping into the middle of a blood feud, how can you expect Henry
to ignore Andre? Henry's only interest in this group is attacking Andre.
You may want to do some more reading in your psychology textbook.

This is similar to the situation that went on for so long between Patrick
and Phil A., where Patrick just couldn't ignore Phil's posts. Amazingly
however Patrick seems to have been able to ignore Phil recently, although
asking that of Henry may be asking too much.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

"Chris Hornbeck" wrote in message ...
I'd be interested in knowing what an RF vector network
analyzer *was*. Been too far outa the loop lately, obviously.

A device that that allows you to make very accurate complex impedance
and transmission measurements (magnitude and phase) of RF networks
over a wide range of frequencies.

Info he http://www.n2pk.com

Normally, a VNA is a very expensive machine, but this clever design
uses modern parts to achieve the same results at very low cost.

I'm also building a new phono equalizer. I'm leaning toward
a long-loop design, but could be convinced to bring the
feedback point from the output of the second voltage gain
stage rather than from the output of the followers.

Topology is complementary all the way; diff-JFET first stage;
unique second stage with complementary JFETs with sources
floating but connected together by a small bias resistor;
junction of output drains feeding followers and (possibly)
EQ feedback network; other drains to power supply rails.
(Diff-in, single-ended out; cool, eh? How come I'm not rich?)
The usual DC servo's, etc. Nakamichi type power supply ground
decoupling. Yada, yada.

Makes me think I should do it with transistors and be done with it.
Another design that is 180 degrees opposite from your approach,
yet still very interesting, is the Pass Pearl phono preamp. Single-
ended, zero feedback FETs. It's supposed to be pretty good.

-Henry

-Henry

"John Byrns" wrote in message ...
This question is not meant as criticism of your general comments on
"swinging chokes". Are you sure that it is true that "The reason swinging
chokes are so rare nowadays is that the availability of cheap silicon
rectifiers and large electrolytic capacitors makes capacitor-input filters
more economical to build than choke- input filters"? My observation is
that chokes of any sort, "swinging" or filter, were gone from Hi-Fi amps
even before the use of silicon rectifiers became common, and also long
before large electrolytic capacitors came on the scene, which appear to
have come later than silicon rectifiers.

You're the hi-fi historian, so I won't disagree. Most of the commercial
hi-fi designs I'm familiar with used a tube rectifier, smallish electrolytic
capacitors, and a small smoothing choke in the main B+ supply. Some,
like the Marantz 8, used solid-state diodes but still retained the choke.

Choke input filters, I think, were always costly. Regardless of the
economics of power supply design during the interim period you refer
to, in the present day the cost advantage of capacitor-input filters is
clear. This ignores any ostensible performance advantages of the
choke-input power supply.

-Henry

John:

Hope springs eternal...

And so forth.

But, for anyone to take much of anything on usenet more seriously than
say... a small hangnail or a bad-hair day (not applicable in my case)
demonstrates a certain amount of silliness. Writing for myself, I take
none of what happens here personally and I try to maintain a certain
(dry) sense of humor through it all. Mr. McCoy is nothing more than a
windbag (and a pretty cold one at that), and that he purports to be a
designer, further that his 'design' has any functional utility or
functional merit sets him up for any criticism that might come his way.
That he has made actionable accusations against Mr. Pasternack (and
others, apparently) should make him glad that he is some thousands of
miles away and has done nothing for which he might be extradited. That
he sticks by them despite your attempt to show him otherwise
demonstrates his irrationality as well as his lack of skill.

That Mr. Pasternack has taken it upon himself to deflate Mr. McCoy's
claims at every opportunity is at one level an unhappy choice as he
will _never_ change McCoy. At another level, at least any casual
visitor who might be tempted to emulate McCoy's designs will do a
modicum of reseach first and then run (not walk) away. So, if either of
them could be characterized as providing a service, that would be Mr.
Pasternack.

And as an outsider, and in a macabre sort of way, it is endlessly
amusing to see Mr. McCoy spin his errors into things that are the fault
of others. He is quite adept at the fallacy of leaping to conclusions
coupled with false premises and circular reasoning. That is three of
seven (possible) fallacies... a gifted writer and user of the English
Language, even if his actual content is negligible. He and
Bulwer-Litton have much in common as gifted hacks... But Litton was
paid by the word... McCoy must pay to have his words published. Note
also that Bulwer-Litton also wrote a hack-novel about a race of unseen
supermen... eerie, isn't it?

Edward Bulwer-Litton Bulwer-Litton is the author of The Coming Race
(1871), a utopia about an underground race of supermen.

McCOY, ANDREW; (1945- )
The Meyeresco Helix (Grafton 0-586-07292-7, Sep '88 [Oct '88],
£3.50, 416pp, pb) Near-future thriller about a superhuman being. [Not
seen]

I would also expect that you, as his friend, amanuensis and sycophant
would hasten to help him come up with a proper series of designs rather
than letting him spring his half-baked bunk (to quote Mr. Stewart) onto
an unsuspecting public. Given your expertise, history and experience,
that should be an easy thing for you, it would certainly have saved
MANY threads of needless vituperation... and given your general
self-effacing character, I am sure you would have been happy for Mr.
McCoy to actually bask in adulation (for your design) for well-executed
designs rather than having vultures picking over the dead corpse of his
design(s). Certainly, Mr. McCoy would be happy to take your design
whole-cloth... you may wait a considerable time before public
acknowledgement, however.

Peter Wieck
Wyncote, PA

Henry Pasternack wrote:

"John Byrns" wrote in message ...
This question is not meant as criticism of your general comments on
"swinging chokes". Are you sure that it is true that "The reason swinging
chokes are so rare nowadays is that the availability of cheap silicon
rectifiers and large electrolytic capacitors makes capacitor-input filters
more economical to build than choke- input filters"? My observation is
that chokes of any sort, "swinging" or filter, were gone from Hi-Fi amps
even before the use of silicon rectifiers became common, and also long
before large electrolytic capacitors came on the scene, which appear to
have come later than silicon rectifiers.

You're the hi-fi historian, so I won't disagree. Most of the commercial
hi-fi designs I'm familiar with used a tube rectifier, smallish electrolytic
capacitors, and a small smoothing choke in the main B+ supply. Some,
like the Marantz 8, used solid-state diodes but still retained the choke.

Choke input filters, I think, were always costly. Regardless of the
economics of power supply design during the interim period you refer
to, in the present day the cost advantage of capacitor-input filters is
clear. This ignores any ostensible performance advantages of the
choke-input power supply.

-Henry

To a large degree the swinging choke was found in power supplies used with Class B, PP modulators as seen in
the 30's & 40's. They were probably used in public address systems with Class B amplifiers as well. Fidelity
was not a concern in those applications. Just lots of audio without too much demand on the power supply.

Cheers, John Stewart

"John Stewart" wrote in message ...
To a large degree the swinging choke was found in power supplies used with
Class B, PP modulators as seen in the 30's & 40's. They were probably used
in public address systems with Class B amplifiers as well. Fidelity was not a
concern in those applications. Just lots of audio without too much demand on
the power supply.

I can't say I've actually seen a hi-fi-schematic with a swinging choke. I do have
a very old one of these, NOS, in its original box, stored in my attic. It's an ugly
little thing, with cloth leads and an unevenly stacked core. Perhaps it was made
by Stancor. I wouldn't use it in a project, but it has interest value as an antique.

Off hand, it seems like a bad idea to put such a wildly nonlinear component into
a power supply. Then again, you could say the same thing about a rectifier.

-Henry

Andre Jute wrote:

Peter:

It is quite clear to me that you are totally out of your depth here and
in your other posts in this thread. Here are just some samples:

1. You appear not to understand the rationale behind the various power
supply topologies and in particular how a choke input works or why it
is traditionally built with two sections, meaning two chokes.

Not traditionally built in two sections at all. That is a special case. If
you put one section in the -ve lead & the other in the +ve lead the common
mode voltages if they are present will be stopped. But then you need to be
aware of other possible problems!

When it comes to protecting the rectifier(s) from excessive peak currents as
seen in cap input filters a single section choke of at least the critical
inductance will do just fine. No need at all for that 2nd
winding. JLS

John Byrns wrote:
In article .com,
" wrote:

Henry:

Just ignore Mr. McCoy. He is no technician certainly and his design
credentials are well-established.

Peter,

You are jumping into the middle of a blood feud, how can you expect Henry
to ignore Andre? Henry's only interest in this group is attacking Andre.
You may want to do some more reading in your psychology textbook.

This is similar to the situation that went on for so long between Patrick
and Phil A., where Patrick just couldn't ignore Phil's posts. Amazingly
however Patrick seems to have been able to ignore Phil recently, although
asking that of Henry may be asking too much.

Regards,

John Byrns

Surf my web pages at, http://users.rcn.com/jbyrns/

There are now more child molesters, flaming idiots and silicon slime on
RAT than there are doers. If you and Patrick and I were to take our
summer holiday all at once, the riffraff would have nothing to talk
about, and if we return in the winter RAT would be dead with mold
growing over it.

I shall have to spend the entire summer cycling. A commission to
design a range of bikes absolutely demands it. Golly, I'm such a
workaholic. I trust you fellows will feel suitably sorry for me from
the comfort of your air-conditioned offices while I brave the dangers
of chlorophyll poisoning, oxygen overload, sunburn, lunches in small
country pubs at the end of leafy lanes in which you can get lost for
several hours, afternoon dips in lonely bays and lakes to soothe
stretched muscles, etc. It's a hard life but someone has to live it.
Here's a piccie of me hard at work:
http://members.lycos.co.uk/fiultra/B...20routine.html

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

John:

You are ****ing up a rope... Mr. McCoy has it in his mind that his is
the way. It has nothing to do with good design, good practice or
anything much else containing the concept of 'good'.

It is, however, a matter of Faith.

In that regard, there is nothing to be done or written that will cause
an alteration in the mind of Mr. McCoy.

Speculation: Has both power *AND* signal ever been applied to Mr.
McCoy's amp with actual speakers also attached? I think not.

Peter Wieck
Wyncote, PA

Oh, KEEERist...

Sports cars
Yachts
Amps
Bicycles
And sending people home in boxes....

Definitely a man of many parts.

None real, however.

Peter Wieck
Wyncote, PA

"Henry Pasternack" wrote in message
...
"Patrick Turner" wrote in message
...
Well, Si diodes and high value cap input filters are better regulated
than any
tubed choke input filter. Gone is the series resistance of choke and
tube.
The choke input allowed the tube rectifier to conduct throughout the
cycle;
there is no peak charging that had limits with tubes.

It seems to be a strong concensus among subjective-minded hobbyists that
choke-input filters sound better because a lot less RF hash is generated
by
diode switching. Even Morgan Jones, who's a pretty no-nonsense guy and
not at all afraid of silicon, thinks so. The argument makes sense to me.

This doesn't mean, though, that a given amplifier built with a cap-input
power supply will sound bad. There are many counter-examples.

Well if the choke is simply able to comply with RL / 1,100 where RL is
the Edc / Idc and Idc is considered at 10% of that normally drawn, the
choke is probably ok for choke input with a higher V ac HT winding
to produce the same B+.

There are a couple of concerns. The first is that the choke should have a
high enough current rating that it won't saturate with the large AC
currents
flowing through it in this application. Manufacturers don't spec their
chokes
for choke-input service and don't publish detailed design information, so
you have to make educated guesses.

The second concern is that the choke has to be made well enough that it
can withstand the added stress due to magnetostriction and core heating.
Hammond, which is the biggest supplier of affordable chokes in North
America, specifically states that their chokes are not rated for use in
choke-input filters. I don't know exactly what they mean by this. I have
a pair of Hammond 10H @ 300mA, 60 Ohm, chokes that run absolutely
cool and quiet as input chokes with a 1000VCT power transformer and
200mA DC load current.

Hi Henry,
Interesting experience with the Hammond chokes. I tried their 5H 500 mA
choke with a 1250 VCT trans @~250mA years ago in a choke input config and
while it was a very stiff supply, the choke buzzed like nuts. I actually
called Hammond about this and they said they would have to specially "dip" a
choke for this app. This was about 1992 so things may have changed since
then. I know the 1650 outputs went through a redesign since as my 100 w 1650
OPT's are significantly heavier / larger then the current offering. This
was also when I learned about critical inductance in a choke input filter.
Good thing I did have 1000v of caps in place when I first fired up that
supply. Sowter also has a separate series of chokes for choke input filters.

MarkS


Nobody is perfectly competent. I do not post with purpose to point out
mainly the incompetence of others, but more to offer an alternative which
may or may not appear to be truer than what else may have been said, or
to augment what has been said already.
I found teachers who came at me to primarily kick my butt of ignorance
to be rude.

Sometimes there is no choice but to kick the ass of a disruptive student.

-Henry

On 5 Apr 2006 17:09:28 -0700, "Andre Jute" wrote:

I shall have to spend the entire summer cycling. A commission to
design a range of bikes absolutely demands it.

BWAHAHAHAHAHA!

Yet *another* 'glittering career' dragged from the mouldering depths
of your tortured imagination, Jute'?

Here's a hint - square wheels are *not* a 'daring design statement'.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

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On Wed, 5 Apr 2006 16:29:46 -0400, "Henry Pasternack"
wrote:

"Chris Hornbeck" wrote in message ...

I'm also building a new phono equalizer. I'm leaning toward
a long-loop design, but could be convinced to bring the
feedback point from the output of the second voltage gain
stage rather than from the output of the followers.

Topology is complementary all the way; diff-JFET first stage;
unique second stage with complementary JFETs with sources
floating but connected together by a small bias resistor;
junction of output drains feeding followers and (possibly)
EQ feedback network; other drains to power supply rails.
(Diff-in, single-ended out; cool, eh? How come I'm not rich?)
The usual DC servo's, etc. Nakamichi type power supply ground
decoupling. Yada, yada.

Makes me think I should do it with transistors and be done with it.
Another design that is 180 degrees opposite from your approach,
yet still very interesting, is the Pass Pearl phono preamp. Single-
ended, zero feedback FETs. It's supposed to be pretty good.

Here's an alternative, using *lots* of tiny transistors! :-)

http://www.lurcher.org/ukra/stewart_p/stewart_p.html
--

Stewart Pinkerton | Music is Art - Audio is Engineering

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