Not to open a bag of worms or anything, but what (if any) are the
advantages/disadvanteges of a CRC filter vs a CLC filter in a power supply?

Asides from the higher cost and larger size of a choke, is there any reason
to choose one over the other?

One more question about chokes has to do with sizing. How does one determine
what size choke to use?
_________________
Rod

www.dortoh.ca

Just one thing : Duncans PSU designer ......
http://www.duncanamps.com/software.html



"lazyadm1n" schreef in bericht
...
Not to open a bag of worms or anything, but what (if any) are the
advantages/disadvanteges of a CRC filter vs a CLC filter in a power
supply?

Asides from the higher cost and larger size of a choke, is there any
reason
to choose one over the other?

One more question about chokes has to do with sizing. How does one
determine
what size choke to use?
_________________
Rod

www.dortoh.ca

Ronald wrote:

Just one thing : Duncans PSU designer ......
http://www.duncanamps.com/software.html

I tried the free program.

It was very slow to use, and I dunno if it even gives the correct results.

For example, I have a solid state amp I am rebuilding,
and I have 65 vrms from the mains tranny,
and I plan to use solid state rectifiers, 250 mH chokes, and 10,000 uF
caps on the rails.
The idle load is about 200 ohms.

Anyway, I typed all that info into program OK, and
I hit 'simulate' and the voltage at the 10,000 uF ( 10 milli farads ) cap
and 200 ohm load
is shown soaring to +85v just after switch on then settling down to +57
volts, which was about
what I calculated on the back of an envelope.

I am not so sure I have seen the soaring voltage in the second or two
after turn on with an LC input filter.

The program also warned me thatbthe PIV of the diodes had been exceeded by
hundreds of volts,
but hey, I only got 65 volts at the sec....

Any comments ?

Patrick Turner.

Patrick Turner wrote in message ...
Ronald wrote:

Just one thing : Duncans PSU designer ......
http://www.duncanamps.com/software.html

I tried the free program.

It was very slow to use, and I dunno if it even gives the correct results.

For example, I have a solid state amp I am rebuilding,
and I have 65 vrms from the mains tranny,
and I plan to use solid state rectifiers, 250 mH chokes, and 10,000 uF
caps on the rails.
The idle load is about 200 ohms.

Anyway, I typed all that info into program OK, and
I hit 'simulate' and the voltage at the 10,000 uF ( 10 milli farads ) cap
and 200 ohm load
is shown soaring to +85v just after switch on then settling down to +57
volts, which was about
what I calculated on the back of an envelope.

I am not so sure I have seen the soaring voltage in the second or two
after turn on with an LC input filter.

The program also warned me thatbthe PIV of the diodes had been exceeded by
hundreds of volts,
but hey, I only got 65 volts at the sec....

Any comments ?

Patrick Turner.

Yes: you're learning something.

NT

"N. Thornton" wrote:

Patrick Turner wrote in message ...
Ronald wrote:

Just one thing : Duncans PSU designer ......
http://www.duncanamps.com/software.html

I tried the free program.

It was very slow to use, and I dunno if it even gives the correct results.

For example, I have a solid state amp I am rebuilding,
and I have 65 vrms from the mains tranny,
and I plan to use solid state rectifiers, 250 mH chokes, and 10,000 uF
caps on the rails.
The idle load is about 200 ohms.

Anyway, I typed all that info into program OK, and
I hit 'simulate' and the voltage at the 10,000 uF ( 10 milli farads ) cap
and 200 ohm load
is shown soaring to +85v just after switch on then settling down to +57
volts, which was about
what I calculated on the back of an envelope.

I am not so sure I have seen the soaring voltage in the second or two
after turn on with an LC input filter.

The program also warned me thatbthe PIV of the diodes had been exceeded by
hundreds of volts,
but hey, I only got 65 volts at the sec....

Any comments ?

Patrick Turner.

Yes: you're learning something.

So what do you think I'm learning?

Patrick Turner.



NT

Patrick Turner wrote in message ...
"N. Thornton" wrote:

Patrick Turner wrote in message ...
Ronald wrote:

Just one thing : Duncans PSU designer ......
http://www.duncanamps.com/software.html

I tried the free program.

It was very slow to use, and I dunno if it even gives the correct results.

For example, I have a solid state amp I am rebuilding,
and I have 65 vrms from the mains tranny,
and I plan to use solid state rectifiers, 250 mH chokes, and 10,000 uF
caps on the rails.
The idle load is about 200 ohms.

Anyway, I typed all that info into program OK, and
I hit 'simulate' and the voltage at the 10,000 uF ( 10 milli farads ) cap
and 200 ohm load
is shown soaring to +85v just after switch on then settling down to +57
volts, which was about
what I calculated on the back of an envelope.

I am not so sure I have seen the soaring voltage in the second or two
after turn on with an LC input filter.

The program also warned me thatbthe PIV of the diodes had been exceeded by
hundreds of volts,
but hey, I only got 65 volts at the sec....

Any comments ?

Patrick Turner.

Yes: you're learning something.

So what do you think I'm learning?


I guess that there are complications that you might have not
appreciated before.

Take overshoot: the L acts like a flywheel. The switch on current
surge into C2 puts a fair bit of energy into the choke, and it tries
to keep that current going when C2 has reached working V, so you get
overshoot.

Diode voltages: Firstly a 65v secondary will give you much more than
65v. 65v rms is ballpark 100v peak. If the transformer has say 10%
regulation, then when unloaded that will actually be 110v peak. It
will be unloaded during V overshoot. Now add to that mains borne
noise, spikes etc. Now add the fact that each diode will see that peak
transformer's output when the cap V is of opposite polarity, so that
adds another V_overshoot onto your diodes V_it_handles.

A small cap across the TF secondary can reduce noise and spikes. It
acts as an RC filter.


NT

"Ronald" wrote in message
...
Just one thing : Duncans PSU designer ......
http://www.duncanamps.com/software.html

Bah... automation ruins the learning process. It's good tool but doesn't
solve errors between the keyboard and operator...

In a word: regulation.

Anything from 10mH for high amperage supplies to 10H on thinner (say, down
to 10-20mA) loads is acceptable. Actually the load doesn't matter, it's the
capacitors - but it's absurd to use 4,700uF and 20mH filtering 10mA of
+300V!
10mH feeding 20uF is useless, because the attenuation is nil.

Typically, the first cap is chosen to be around 500uF per ampere (less for
tube rectifiers), the second cap a bit larger (up to 4 times) to store
energy to supply momentary demands of the amplifier. The choke is typically
chosen to give between 10 and 200 times attenuation (i.e., around -20
to -50dBV) of the ripple on the first cap.

For CRC filters, the resistor is chosen similarly, or to drop a certain
voltage. If it drops too much for your requirements, you might have to use
more capacitance after it to get sufficiently low hum; likewise, if you need
to drop a lot of, and a certain amount of voltage, you might take that route
instead.

Tim

--
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms

Advantages:

1 - The choke has a much lower DC resistance for the same hum attenuation,
hence it doesn't drop voltage unnecessarily
2 - The choke filters high frequencies (diodes commutation "spikes" and/or
radio noise & other HF garbage coming in thru the AC line) very effectively,
'cause its impedance increases with frequency
3 - The choke STORES energy, this is why it smoothens DC much more than a
simple R
4 - The choke dissipates less heat than a R giving comparable filtering
5 - Since the L draws a constant current, it allows tube rectifiers to give
much more in LC filter arrangement than in CLC (the tube is never forced to
give violent current pulses as with a C connected to cathode)

Disadvantages:

1 - the choke is big, heavy and expensive
2 - the choke is a source of electromagnetic noise; if used in a phono
preamp it should be screened (potted), and in any case it should be
installed "rotated" with respect to other magnetic components in order not
to "mix" stray magnetic fields, which is not always easy

Briefly:

Any "serious" PS needs to use a choke. Its value is a matter of $, weight
and requirements. Ordinary power amps are happy with anything between 2 and
10H, the PP being less demanding. The more the current, the smaller the L
value for the same pounds of iron. For preamps a larger value is good, I
used a 40H choke to supply less than 20 mA to my line preamp (a single ECC81
cathode-follower). There's a diode bridge, a 47uF, the choke, another 47uF,
then 2 resistors 1k5 each feeding two 10uF capacitors, finally feeding the
ECC81 anodes. Cap values are small, but the 40H smoothens the power so
effectively that when I put the 'scope probe on the 10uF cap I did not
manage to see anything like a sine wave.

Ciao

Fabio


"lazyadm1n" ha scritto nel messaggio
...
Not to open a bag of worms or anything, but what (if any) are the
advantages/disadvanteges of a CRC filter vs a CLC filter in a power
supply?

Asides from the higher cost and larger size of a choke, is there any
reason to choose one over the other?

One more question about chokes has to do with sizing. How does one
determine what size choke to use?
_________________
Rod

www.dortoh.ca

Fabio Berutti wrote:

Advantages:

1 - The choke has a much lower DC resistance for the same hum attenuation,
hence it doesn't drop voltage unnecessarily

I like chokes, and use them in all my power amps.


2 - The choke filters high frequencies (diodes commutation "spikes" and/or
radio noise & other HF garbage coming in thru the AC line) very effectively,
'cause its impedance increases with frequency

True, but a lot of the diode noise is caused by stray inductive and capacitive
pick
up by input leads of the pulses of resonant F created by the leakage L of the
power tranny
and the shunt C available. Often a 0.05 across the HT seconday will
move this F down to one which won't travel.

Where you have a CLC, one can often have a small C + R across the L,
so that this C and the L are resonant at twice the mains F,
and so the L+C form a parallel resonant circuit which
rejects the ripple F much better.
To stop higher harmonics getting thru via the small C, the R in series
is about 20 ohms, and forms a damping R to the tuned circuit.
Such a $2 solution increases the ripple rejection about 15 dB,
so its like using a choke 5 times the value.




3 - The choke STORES energy, this is why it smoothens DC much more than a
simple R

Well, not really. If the impedance of a 1H choke is 628 ohms at 100 Hz,
the choke will filter only as well as a 628 ohm resistance at 100 Hz.
But the choke forms a second order LC filter with C2 of the CLC,
abd *this* is the big advantage with the choke.

However where you have CRCRC, the LF ripple caused by mains voltage
undulations tend to be better filtered than with CLCLC,
so for preamps, I may have a small choke in a CLC to start with,
but then its all CRCRC down to the MC amp.
And I use lots of 470 uF electros with 2 uF plastic caps to bypass them close to
where the
tubes are connected, because one don't want stray RF finding its way around,
and the cascode MC amps I use were prone to RF oscillations until
I made all the leads less than 20mm, ie, treated the circuit as if it was an
RF circuit.
I used choke feeds from the DC supply for the heaters to the 6EJ7
cascoded MC amp tube, with ceramic C bypasses to 0V, just to make sure
RF noise couldn't find its way around the heater circuit.

4 - The choke dissipates less heat than a R giving comparable filtering

This is a major advantage in a power amp, but not so major
in a preamp.


5 - Since the L draws a constant current, it allows tube rectifiers to give
much more in LC filter arrangement than in CLC (the tube is never forced to
give violent current pulses as with a C connected to cathode)

The current in chokes varies.

But what you refer to is the LC filter, not CLC filter.
The LC filter, known as a choke input supply does have a major
benefit; the flow of DC is constant from the rectifiers, and there
are no pulse charges to the C1 of a CLC or CRC type of
capacitor input supply.
So a choke allows tube rectifiers to be used, and tube rectifiers have very
restricted peak current handling, so C1 has to be limited to say
47 uF max in a CLC or CRC supply.

The disadvantage of the LC input is the cost of the input choke,
which has to be very carefully made, to prevent
mecanical hum, and radiated fields and vibration, and
interaction with steel chassis.
And getting the choke to just the right value, gap size,
and DC resistance is a bother.

And the power tranny winding has to have a lot higher voltage to get the same
value of B+.




Disadvantages:

1 - the choke is big, heavy and expensive
2 - the choke is a source of electromagnetic noise; if used in a phono
preamp it should be screened (potted), and in any case it should be
installed "rotated" with respect to other magnetic components in order not
to "mix" stray magnetic fields, which is not always easy

Potting is almost mandatory with LC filters.
But not with CLC filters because the amount of AC flow in the CLC filter
is usually a tiny fraction of the AC in an LC filter.



Briefly:

Any "serious" PS needs to use a choke. Its value is a matter of $, weight
and requirements. Ordinary power amps are happy with anything between 2 and
10H, the PP being less demanding. The more the current, the smaller the L
value for the same pounds of iron. For preamps a larger value is good, I
used a 40H choke to supply less than 20 mA to my line preamp (a single ECC81
cathode-follower). There's a diode bridge, a 47uF, the choke, another 47uF,
then 2 resistors 1k5 each feeding two 10uF capacitors, finally feeding the
ECC81 anodes. Cap values are small, but the 40H smoothens the power so
effectively that when I put the 'scope probe on the 10uF cap I did not
manage to see anything like a sine wave.

High value chokes are not so easy to come by,
so for wherever I can, I prefer CRCRC for preamps, and use a high
B+ to start with to allow for filering down with R.
And if I use a 47 uF off a tube rectifier, I will
have say at least 340 ohms before the next C.
The 47 uF has 34 ohms of reactance at 100 Hz.
To make sure the tube rectifier isn't loaded by even more reactance of a second
C, R should be at least 10 x ZC, so 340 ohms ( or more, whatever suits..)
Then I don't muck around, I use 470 uF for the next C.
Then another R, but its value doesn't have to be large, say
330 ohms, and the DC voltage drop in a preamp won't be large,
and then another 470 uF cap.
470 uF has only 3.4 ohms of reactance, so the 330 ohm
plus 470 uF gives a hum attenuation of 100 times or 40 dB.

So if you had 5 volts of ripple at the 47 uF off the rectifier,
then after two 330 ohms and two 470 uF, the hum
will be 10,000 times lower, or -80 dB, so 0.5 mV.

If the preamp current was only 30 mA, the voltage drop
in 660 ohms is only 20v.

I like to start with a HT winding of 240v on the power tranny, giving
me 340v off the rectifier, then I can afford to
drop down to 280v for the preamp stage supplies.

Caps are cheaper and easier to source than chokes.

If you want more attenuation of the hum, and I would,
then use say 47 uF, 330 ohms, 470 uF, 470 ohms, 470 uF,
and then perhaps have 4k7 and 100 uF to each tubes anode supply point.
This should stop all the stages talking to each other.


Sometimes the use of chokes in LC inputs can solve a problem.

I recently made a supply for a rebuilt solid state amp which had 62vrms
windings.
I didn't want the possible +/- 87 volt rails with a cap input.

With an LC filter, the B+ rail is 0.88 x the rms value of the winding voltage,
if the DC resistances of the choke is low, and the R of the rectifiers is low.

So I figured about +/- 54v for the rails would be just right.
So one has to design the choke to suit the conditions and the pocket.
I wanted 220 mA at idle for the amp, and up to 4 amps at a couple of hundred
watts of output,
using the 54 volt rails.

The smallest current to be drawn by a circuit is where you start,
and the circuit is a load on the supply, and it's highest ohmic value is found
by the wanted B+ divided by the DC current at idle.
This supply is for an AB amp where the current increases, but we must
find the L for the highest value of RL we will have.

Where the mains is 50 Hz, L = RL / 940,
so in my case V = 55v, I = 0.22amps DC, so RL = 55/0.22 = 250 ohms.

So L wanted = 250 / 940 = 0.266 Henrys.

I want the choke to handle up to 4 amps DC,
so I want to have only 4 volts maximum drop in DV due to the choke's DCR,
so after checking out what my little yellow book which is a guide to choke
design,
and doing a run with the Hanna method,
I came up with a choke with wasteless pattern iron, 50 stack, 25mm tongue,
and 345 turns of 1.25mm wire.
This gave me a DC resistance just under one ohm, and hopefully enough L.
One never knows until one is done.

After 2 hrs of careful layer winding and getting all sticky with varnish as I
wound ans assembled it,
I tried this choke in the circuit. with 250 ohms as the load, and 10,000 uF as
the cap
from which the collector circuit would operate.
I arranged a 32 ohm load to simulate a higher load current test.

The air gap has to be set for optimum.

A choke in this situation is called a swinging choke, because
when Idc = 0.22 amps, we want L to be high, and when
its say 2.2 amps, we allow it to reduce due to the increasing DC flow
causing the iron to have a lower U factor, and thus less L.

If you have the gap too large, the amount of L will be too low
when Idc is low, and the input voltage will tend to saturate the core,
and you will get nasty step in the 100 Hz wave form at the
diodes. But if the choke has a gap too small, it might saturate
with DC, at high current, and the smoothing action is minimised.

So I added strips of paper to each side of the Is in the E&I assembly,
and recorded the ripple voltage at the load as the gap was adjusted.

With no gap, the ripple was lowest with low current, and highest with high dc
current.

With more gap, the ripple slightly increased with low current, but fell
considerably with high current.
Then with 4 sheets of paper the value of L fell below the
calculated **critical value** for maintaining B+ = 0.89 v winding vrms,
and it began to saturate, and the wave form at the output of the diodes
looked awful, instead of a nice series of arches.

So I backed off with gapping, and settled for 3 sheets of paper.

This was enough gapping to stop the choke saturating due to too much DC.

Then I measured the value of inductance at 0.22 amps, and 1.9 amp.

This may seem difficult, but it isn't, and approximate measure will do.

The ripple voltage at 0.22 amps DC at the 10,000 uF was measured to be 0.02
vrms, 100 Hz.
The 100 Hz voltage across the choke was 27vrms, so
the reactance of the capacitor is much smaller then the chokes, when you
consider
equal ac current flows through each to ground from the rectifier.

The ratio of voltages is 27 / 0.02 = 1,350.
Now the reactance of the cap is only 0.16 ohms at 100 Hz, so
the reactance of the choke must be 1,350 x 0.16 = 216 ohms,
and since there is 628 ohms per Henry at 100 Hz, the choke's value must be
216 / 628 = 0.34 Henries, which is slightly above
the critical value we were aiming for at the beginning.

At 1.9 amps of dc, the ripple voltage at the 10,000 uF was 0.06 vrms,
and since the voltage across the choke is substantially constant at 27 vrms,
the choke's reactance was calculated at 73 ohms, so
its value has fallen to 0.12 Henrys at the 1.9 amp dc.

Between 0.22 amps and 1.9 amps, the B+ fell from +55v to +53v,
only about 4%, which is quite satisfactory for a class B amp.

With tube amps the same procedure can be followed, and for the same
**power** involved, the choke will have more turns, the cap will be
less uF, the load will be more ohms, but the choke will remain about the same
size.

The RDH4 has the Hanna method spelled out fairly clearly, but you really
have to guess about what you need for size to begin, and that comes from
experience.
The Hanna method allows the turns to be precisely calculated for the least
DC drop, and suitablity for the current change.

As the value of inductance is reduced below the critical value for a given DC
current,
the B+ will rise, so that when L = 0.0, it will have risen to
a max of 1.41 x the rms value of the winding voltage.

With swinging choke situations like the one I have exampled,
one has to allow for at least 10% of the maximum current to be drawn
by the AB amp to prevent the B+ from reaching the unwanted value
of a cap input filter, which would explode the electrolytics
if they were not rated well.
Often a "bleeder" resistance is used, like the 250 ohms in the example above.
At idle, such an R dissipates 15 watts, so it needs to be rated for 50,
to prevent it fatiguing, going open, and allowing B+ to soar too high.

Although I have given a solid state example, choke inputs are best in tube amps.

The B+ regulation for a class AB amp is poorer for a given
tube rectifier and C than when the same rectifier is used with a choke
in front of the C and the winding voltage is made higher to
get the same B+.

The lower the DCR of the choke, the less it heats up.

The AC dissipates very little heat in the choke.
The DC current is the main cause of heat.
Dissipation = I x I x R and so if I is doubled, the heat increases 4 times.

In a class A amp, the current to the amp never varies, so there is no point
in seeking the better regulation of a choke input, and so
the CLC can be used, and the choke need only be a fraction of the size
as used for the LC input.

Now if you all followed all that, we give out medals...

Lodge your complaints about electro-magnetism with
God Of Triodes,
69 Gold Street,
Heaven.

Patrick Turner.

Lodge your complaints about electro-magnetism with
God Of Triodes,
69 Gold Street,
Heaven.

Patrick Turner.


Inter-continental post fare applied, isnt'it?

Fabio

Fabio Berutti wrote:

Lodge your complaints about electro-magnetism with
God Of Triodes,
69 Gold Street,
Heaven.

Patrick Turner.

Inter-continental post fare applied, isnt'it?

Yeah, and they apply HST as well ( HST is like a goods and services tax,

or VAT, only in this case is a Heaven Sent Tax..)

Economic rationalism is going on up there too ;-)

Patrick Turner.



Fabio

"Fabio Berutti" wrote in message ...

Any "serious" PS needs to use a choke.

While your list of pros was very good, I'm not personally convinced
about the above claim. There are various ways to catch a rat, and CLC
supplies arent the only one. Modern amps almost never use them...
because they are not essential IMHO.

Regards, NT

I admit, I used a categoric statement which is not necessarily true. There
are stabilised PS and many more "engineered" designs to do the job. I was
thinking only about a comparison among CLC and CRC "plain" filters. As per
the modern amps, I suppose that size, weight, appearence and $ have
something to do with the reduction in the kg of Si-iron used in these
designs (sand-state devices are excluded: I guess that, because of their
high current and low voltage requirements, a choke would need to be some 50
pounds to do its job, while a 317 or the like will cost a song and work
perfectly).

Ciao

Fabio


"N. Thornton" ha scritto nel messaggio
om...
"Fabio Berutti" wrote in message
...

Any "serious" PS needs to use a choke.

While your list of pros was very good, I'm not personally convinced
about the above claim. There are various ways to catch a rat, and CLC
supplies arent the only one. Modern amps almost never use them...
because they are not essential IMHO.

Regards, NT

"N. Thornton" wrote:

"Fabio Berutti" wrote in message ...

Any "serious" PS needs to use a choke.

While your list of pros was very good, I'm not personally convinced
about the above claim. There are various ways to catch a rat, and CLC
supplies arent the only one. Modern amps almost never use them...
because they are not essential IMHO.

The reason they are not used today is cost,
and the availability of reliable large value electros.
But I still use chokes, and they are still very effective,
and reliable, in comparison to active methods of ripple filtering.

They had more favour when electros were not so reliable,
expensive and large.

But I even got a choke to work well in an LC input filter in a solid state amp supply.
Nobody is supposed to that these days, but I find its works very well.

I did try a sodium lamp ballast but although the ballast was large,
its DCR was more than a smaller one that I wound myself, and the gap was way to big,
to make sure the choke never saturated, and the value of inductance
wouldn't "swing" down from a critical high value to a lower value with increasing DC.

Patrick Turner.




Regards, NT

Patrick Turner wrote in message ...
"N. Thornton" wrote:
"Fabio Berutti" wrote in message ...

Any "serious" PS needs to use a choke.

While your list of pros was very good, I'm not personally convinced
about the above claim. There are various ways to catch a rat, and CLC
supplies arent the only one. Modern amps almost never use them...
because they are not essential IMHO.

The reason they are not used today is cost,
and the availability of reliable large value electros.
But I still use chokes, and they are still very effective,
and reliable, in comparison to active methods of ripple filtering.

They had more favour when electros were not so reliable,
expensive and large.

But I even got a choke to work well in an LC input filter in a solid state amp supply.
Nobody is supposed to that these days, but I find its works very well.

I did try a sodium lamp ballast but although the ballast was large,
its DCR was more than a smaller one that I wound myself, and the gap was way to big,
to make sure the choke never saturated, and the value of inductance
wouldn't "swing" down from a critical high value to a lower value with increasing DC.

Patrick Turner.


Amps with choke psus can work well: after all, the Quad II used them.
But things have moved on, and you can now get much better performance
from a solid state regulated psu, and at lower cost and weight. I
would say if youre really serious about quality one would go with a
proper regulated psu, not the cruder lower performance choke psu.

The downsides of choke psus compared to regulated ones a
very poor regulation
significant impedance
size
weight
cost
resonance
and patchy rejection

In the past reg psus were not much used simply because they were too
pricey. They typically used neon tubes as the Vref, and the pass valve
would have to drop substantial voltage, making the whole setup very
inefficient. Much cruder partial-regulating schemes were sometimes
used like swinging chokes, bleed resistors, baretters, etc.


NT

H RATs!

If you are really serious about quality, you will keep building PS circuits
until you find one that pleases your ears

Unfortunately, no physical dimension correlates perfectly with "I like the
sound."

From a personal standpoint, I have discovered that the joys of audio far
outweigh the efficiencies of retail engineering.

Yes, there have been some nice amps marketed.

No, none of them went very deep into any of the applicable technologies.

I am disabled, and gravel crazy, but sometimes a great notion passes between
these ears.

It is OK for some folks to create realistic designs and workaday
implementations. It seems harmless if some of us just hook stuff up and Listen


Quest into the Unknown!

oh, yeah, and ...

Happy Ears!
Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

"N. Thornton" wrote:

Patrick Turner wrote in message ...
"N. Thornton" wrote:
"Fabio Berutti" wrote in message ...

Any "serious" PS needs to use a choke.

While your list of pros was very good, I'm not personally convinced
about the above claim. There are various ways to catch a rat, and CLC
supplies arent the only one. Modern amps almost never use them...
because they are not essential IMHO.

The reason they are not used today is cost,
and the availability of reliable large value electros.
But I still use chokes, and they are still very effective,
and reliable, in comparison to active methods of ripple filtering.

They had more favour when electros were not so reliable,
expensive and large.

But I even got a choke to work well in an LC input filter in a solid state amp supply.
Nobody is supposed to that these days, but I find its works very well.

I did try a sodium lamp ballast but although the ballast was large,
its DCR was more than a smaller one that I wound myself, and the gap was way to big,
to make sure the choke never saturated, and the value of inductance
wouldn't "swing" down from a critical high value to a lower value with increasing DC.

Patrick Turner.

Amps with choke psus can work well: after all, the Quad II used them.

Indeed, Quad II does have a choke, but its for the screen supply.
meanwhile the anode supply has only 16 uF from the tube rectifier,
and there is about 17 vrms of sawtooth ripple voltage at the CT of the OPT.
Its applied to the circuit in common mode, so the IMD caused by
injection of all this noise is no more than the THD measured in thse amps,
which can vary by as much as 20 dB depending on whether the tubes are matched or not,
so I have found.

So with Quad II, I like to remove the existing large low value C, and
insert mdern 47 uF off the rectifier, then 1.7H lamp ballast choke, then 100 uF
at the CT, thus reducing the hum at the CT to utterly negligible levels.
The IMD caused by PS noise is eliminated.


But things have moved on, and you can now get much better performance
from a solid state regulated psu, and at lower cost and weight.

But not in a Quad II amp, without having a considerable V drop,
and the unreliablity of the SS regulator.



I
would say if youre really serious about quality one would go with a
proper regulated psu, not the cruder lower performance choke psu.

Just use the right values of L&C.
No need for all that SS regulation.
Use of SS diodes is fime though, and a voltage doubler
with SS and CLC will have better reg than tube diodes and LC input filter.

Regulation in tube amps is only needed for class AB amps where they are used hard,
and where the amp is mainly class B.
if you don't believe me, try clipping a meter on the B+
of an average class AB amp B+, and take the music up to a level where
clipping only just starts to be visible on the CRO.
Usually, a supply of +450v moves only few volts.
With a sine wave input, sure, the B+ will move maybe 10%,
but that is still OK.





The downsides of choke psus compared to regulated ones a
very poor regulation

Not if the PT is low R, and diode R is low, and DCR of L is low.

significant impedance

Not if the L is followed by a large enough C.


size

A regulator may use a heatsink, itself needing to be insulated.


weight

OK, but a choke is only one simple element.


cost

Depends how one is set up.

I wind my own, re-cycling old tranny cores...


resonance

Eliminated by those who know what they are doing.


and patchy rejection

Of what?



In the past reg psus were not much used simply because they were too
pricey. They typically used neon tubes as the Vref, and the pass valve
would have to drop substantial voltage, making the whole setup very
inefficient. Much cruder partial-regulating schemes were sometimes
used like swinging chokes, bleed resistors, baretters, etc.

Indeed.

I have only used one regged PS in a power amp,
see in the image at http://www.turneraudio.com.au/webpic...ab400w317h.jpg

Its been going well for about 6 years, but all the power amps since then have chokes,
after I got some partial failures in a preamp. Leakage and spikes
cause death in SS regs all too easily.

I used to have an SS regged bench top test PS, but the BU208 pass element
blew up one evening when a storm was passing.
I wasted several BU208 when doing R&D for this PS.

I switched to a pair of 6AS7G, and a 6BX6 pentode gain tube,
and a switchable LC input filter to vary
the input voltage so there would not be excessive voltage across the 6AS7G
when using high current and low voltage output.

This test supply has never missed a beat in the last 7 years.

But I never would place a plate supply regulator in anything I sold;
it simply is not needed.

Patrick Turner.


NT

"lazyadm1n" wrote in message ...
Not to open a bag of worms or anything, but what (if any) are the
advantages/disadvanteges of a CRC filter vs a CLC filter in a power supply?

Asides from the higher cost and larger size of a choke, is there any reason
to choose one over the other?

One more question about chokes has to do with sizing. How does one determine
what size choke to use?
_________________
Rod

www.dortoh.ca

Fabio gave the best advantages and disadvantages of a reactor. I am
one who always uses a reacor in designs. I tolerate the additional
cost and weight. I want a job done right so I do not have to go back
to it.

The easiest way to determine the amount of henries you need is to
divide the mA into the B+ and that gives the minimum amount of
inductance needed. This is done at static currents. The formulas to
get the exact inductance vs. the easier way are a few percent
difference. It is best to go higher in inductance than lower.

lazyadm1n wrote:

Not to open a bag of worms or anything, but what (if any) are the
advantages/disadvanteges of a CRC filter vs a CLC filter in a power supply?

Asides from the higher cost and larger size of a choke, is there any reason
to choose one over the other?

One more question about chokes has to do with sizing. How does one determine
what size choke to use?
_________________
Rod

www.dortoh.ca

With the CLC filter there will be a resonance, possibly in the AF range.
I used Patrick's proposed values in this simulation. See the results at ABSE.

The resonance appears at about 4.5 Hz. This will have some effect
on the amp's sound. Quite common in most amps using this configuration,
whether tubed or SS.

On the other hand the CRC filter response is smooth but the power
losses are high.

Take your pick. There are no free rides while using simpler topologies.
A relatively easy way out would be a SS filter/regulator. I favor things
like the Int. Rectifier FETs to do the work.

Good Luck with your project, John Stewart

John Stewart wrote:

lazyadm1n wrote:

Not to open a bag of worms or anything, but what (if any) are the
advantages/disadvanteges of a CRC filter vs a CLC filter in a power supply?

Asides from the higher cost and larger size of a choke, is there any reason
to choose one over the other?

One more question about chokes has to do with sizing. How does one determine
what size choke to use?
_________________
Rod

www.dortoh.ca

With the CLC filter there will be a resonance, possibly in the AF range.
I used Patrick's proposed values in this simulation. See the results at ABSE.

Nowhere did I ever suggest all the values for the CLC filter shown in the
test schematic at your post at ABSE.

The values you posted to gain the results for resonance were :-

PS generator resistance = 1kOhm,
C1 = 10mF, which is milli Farads, or 10,000uF,
L = 250 milli Henrys.
C2 = 10mF, which is milli Farads, or 10,000 uF,
RL = 200 ohms.
I assume your model used the questionable Duncan Amps freely
downloadable power supply designer program which I found gave me some
incomprehensible results.

The schematic you posted is misleading to those who
may think that 10mF = 10 uF!!!!!!


I recall the discussions revolved around a
very low generator impedance, ie, a large SS amp
power tranny feeding through SS diodes into an LC filter,
with approx 250 mH and 10,000 uF.

Fo = 3.18 Hz.

The 200 ohms is not low enough to damp the LC resonance,
but for critical damping, 7 ohms is required, so the 1.0 ohm dcR of the choke
effectively in series with the L will still leave the Q of the filter somewhat
higher than desirable,
but I found the voltage stability at the 10,000 uF didn't bounce around
when intermittently shunting the 200 ohm bleeder R with 32 ohms.

In the case of an LC filter, any resonance of the LC circuit
is damped when the value of the inductance changes considerably
with a varying charge rate into the C.
In my case with the LC filters for this SS amp,
the tested L for a 250 ohm load with a +55v rail was 0.35 H, or 350 mH.
When 32 ohms was added to the 250 ohms for total 28 ohms,
Idc became 1.9 amps dc, and L became 0.12 H, or 120 mH.

But the test circuit showed no sign of wild resonance voltage swings.
if there were, the choke goes from being higher L to a low value and which
saturates
for part of the rectifier wave forms, and becomes a very much lower
value of L when it does, so resonance seems damped
since L does not stay at a constant value.

Its not just simple filter theory which is applicable here in this case of
LC power supply filter.


The amp in question will be used as a sub amp, but will still have
input filtering to give a pole at 10 Hz.

I still don't believe the resonance will affect the sound one iota.

The resonance appears at about 4.5 Hz. This will have some effect
on the amp's sound.

There may be some amps which have a resonance in the CLC filter,
or LC filter ot CLCLC filter which may be at just under 5 Hz.

In none of them have I found there is any audible artifact.
In a PP amp, any 5 Hz ripples are applied to the CT and common mode
rejection prevents their appearance in the output signal.
But even in SE amps, I sure don't get such problems in my amps.

I have always recommended the use of very large value C2 in a CLC
filter of a tube amp, 470 uF being typical.

If L = 2H, then the Fo between the 470 uF and the 2H is 5.2 Hz.
At 5.2 Hz, ZC and ZL = 62.8 ohms.
The RL may typically be 1600 ohms, which won't be low enough
to damp the LC resonance critically.
But the L will have typically 50 Ohms of dcR, which is effectively in with the L
value,
and approaching the value of 87 ohms required for a -3 dB maximally flat filter
response with a pole
at 5.2 Hz.
So the resonance Q of the filter will be very low, and I have never found any
LF instability of audible effects using the values just quoted, not even when L =
1 H.
In the last pair of SE amps I sold last month I used
C1 = 470 uF,
L = 1H,
C2 = 940 uF.
The dcR of the choke was only 30 ohms,
and although the LC filter was underdamped, and should have
given a moderately high Q resonance at 5.2 Hz, the amps showed no
resonance problems. The value of critical damping R
would be ZL x l.41, or 32.6 ohms x 1.41, or 46 ohms, and
the dcR of the choke is 30 ohms, so almost enough for
perfect damping.
Should anyone want to counter the effects of resonance better than this,
then add more series R as well as retain the choke.
I didn't want to do this because the B+ would have had to be derived from a higher
tap
on the HT winding, and placed the B+ value at C1 perilously close to the voltage
rating of C1, only +450v.



Quite common in most amps using this configuration,
whether tubed or SS.

Very, very few SS amps have CLC filtering to their rails because
most are designed with stupendous values of C, and whatever ripple voltage
appears at the rails does not get into the circuit because of the higgh collector
resistance and the use of typically 50 dB of loop NFB, along
with typically 30 dB of local feedback in the emitter follower config
of most output stages.

I have used a pair of 100,000 uF caps in my own mosfet amp for
300 watts per channel.
No need for any CLC, but others are welcome to try them.

In another SS 50/50 stereo class A amp, I have used C1 = 9,400 uF,
L = about 150mH, C2 = 45,000 uF.
Fo = 1.93 Hz, and ZC = ZL = 1.8 ohms.
The RL = 6.6 ohms, not enough R to damp the resonance,
since the DCR of the choke is 0.5 ohms.
This class A amp has an OPT, and CR coupling, like a tube amp,
and the circuit has a total of 20 dB of NFB,
and there is no resonance problems at LF whatever,
or stability problems because
the circuit open loop gain is well below unity where the LF phase shift
is 180 degrees.

On the other hand the CRC filter response is smooth but the power
losses are high.

The power losses are low, not high with a CLC filter.

Take your pick. There are no free rides while using simpler topologies.
A relatively easy way out would be a SS filter/regulator. I favor things
like the Int. Rectifier FETs to do the work.

People have been using CLC filters with no sonic problems for years without
resorting to solid state regulators, which always do result in a power
loss, because of the voltage drop x load current across the series
pass element, or the B+ voltage x shunt element in the case of a shunt regulator.

Regulators done with SS power fets or well rated bjt like the BU208 waste power,
CLC filters don't, because of the insignificant power lost
in the dcR of the choke, which totals Idc squared x R, in watts.


Good Luck with your project, John Stewart

I don't think the original poster's luck
will be improved by erroneous advice.

Patrick Turner.

"Patrick Turner" wrote in message
...


John Stewart wrote:

lazyadm1n wrote:

Not to open a bag of worms or anything, but what (if any) are the
advantages/disadvanteges of a CRC filter vs a CLC filter in a power
supply?

Asides from the higher cost and larger size of a choke, is there any
reason
to choose one over the other?

One more question about chokes has to do with sizing. How does one
determine
what size choke to use?
_________________
Rod

www.dortoh.ca

With the CLC filter there will be a resonance, possibly in the AF range.
I used Patrick's proposed values in this simulation. See the results at
ABSE.

Nowhere did I ever suggest all the values for the CLC filter shown in the
test schematic at your post at ABSE.




You mean like this,? posted by Patrick Turner on 10/20/2004?

For example, I have a solid state amp I am rebuilding,
and I have 65 vrms from the mains tranny,
and I plan to use solid state rectifiers, 250 mH chokes, and 10,000 uF
caps on the rails.
The idle load is about 200 ohms.





The values you posted to gain the results for resonance were :-

PS generator resistance = 1kOhm,
C1 = 10mF, which is milli Farads, or 10,000uF,
L = 250 milli Henrys.
C2 = 10mF, which is milli Farads, or 10,000 uF,
RL = 200 ohms.
I assume your model used the questionable Duncan Amps freely
downloadable power supply designer program which I found gave me some
incomprehensible results.

The schematic you posted is misleading to those who
may think that 10mF = 10 uF!!!!!!


I recall the discussions revolved around a
very low generator impedance, ie, a large SS amp
power tranny feeding through SS diodes into an LC filter,
with approx 250 mH and 10,000 uF.

Fo = 3.18 Hz.

The 200 ohms is not low enough to damp the LC resonance,
but for critical damping, 7 ohms is required, so the 1.0 ohm dcR of the
choke
effectively in series with the L will still leave the Q of the filter
somewhat
higher than desirable,
but I found the voltage stability at the 10,000 uF didn't bounce around
when intermittently shunting the 200 ohm bleeder R with 32 ohms.

In the case of an LC filter, any resonance of the LC circuit
is damped when the value of the inductance changes considerably
with a varying charge rate into the C.
In my case with the LC filters for this SS amp,
the tested L for a 250 ohm load with a +55v rail was 0.35 H, or 350 mH.
When 32 ohms was added to the 250 ohms for total 28 ohms,
Idc became 1.9 amps dc, and L became 0.12 H, or 120 mH.

But the test circuit showed no sign of wild resonance voltage swings.
if there were, the choke goes from being higher L to a low value and which
saturates
for part of the rectifier wave forms, and becomes a very much lower
value of L when it does, so resonance seems damped
since L does not stay at a constant value.

Its not just simple filter theory which is applicable here in this case of
LC power supply filter.


The amp in question will be used as a sub amp, but will still have
input filtering to give a pole at 10 Hz.

I still don't believe the resonance will affect the sound one iota.

The resonance appears at about 4.5 Hz. This will have some effect
on the amp's sound.

There may be some amps which have a resonance in the CLC filter,
or LC filter ot CLCLC filter which may be at just under 5 Hz.

In none of them have I found there is any audible artifact.
In a PP amp, any 5 Hz ripples are applied to the CT and common mode
rejection prevents their appearance in the output signal.
But even in SE amps, I sure don't get such problems in my amps.

I have always recommended the use of very large value C2 in a CLC
filter of a tube amp, 470 uF being typical.

If L = 2H, then the Fo between the 470 uF and the 2H is 5.2 Hz.
At 5.2 Hz, ZC and ZL = 62.8 ohms.
The RL may typically be 1600 ohms, which won't be low enough
to damp the LC resonance critically.
But the L will have typically 50 Ohms of dcR, which is effectively in with
the L
value,
and approaching the value of 87 ohms required for a -3 dB maximally flat
filter
response with a pole
at 5.2 Hz.
So the resonance Q of the filter will be very low, and I have never found
any
LF instability of audible effects using the values just quoted, not even
when L =
1 H.
In the last pair of SE amps I sold last month I used
C1 = 470 uF,
L = 1H,
C2 = 940 uF.
The dcR of the choke was only 30 ohms,
and although the LC filter was underdamped, and should have
given a moderately high Q resonance at 5.2 Hz, the amps showed no
resonance problems. The value of critical damping R
would be ZL x l.41, or 32.6 ohms x 1.41, or 46 ohms, and
the dcR of the choke is 30 ohms, so almost enough for
perfect damping.
Should anyone want to counter the effects of resonance better than this,
then add more series R as well as retain the choke.
I didn't want to do this because the B+ would have had to be derived from
a higher
tap
on the HT winding, and placed the B+ value at C1 perilously close to the
voltage
rating of C1, only +450v.



Quite common in most amps using this configuration,
whether tubed or SS.

Very, very few SS amps have CLC filtering to their rails because
most are designed with stupendous values of C, and whatever ripple voltage
appears at the rails does not get into the circuit because of the higgh
collector
resistance and the use of typically 50 dB of loop NFB, along
with typically 30 dB of local feedback in the emitter follower config
of most output stages.

I have used a pair of 100,000 uF caps in my own mosfet amp for
300 watts per channel.
No need for any CLC, but others are welcome to try them.

In another SS 50/50 stereo class A amp, I have used C1 = 9,400 uF,
L = about 150mH, C2 = 45,000 uF.
Fo = 1.93 Hz, and ZC = ZL = 1.8 ohms.
The RL = 6.6 ohms, not enough R to damp the resonance,
since the DCR of the choke is 0.5 ohms.
This class A amp has an OPT, and CR coupling, like a tube amp,
and the circuit has a total of 20 dB of NFB,
and there is no resonance problems at LF whatever,
or stability problems because
the circuit open loop gain is well below unity where the LF phase shift
is 180 degrees.

On the other hand the CRC filter response is smooth but the power
losses are high.

The power losses are low, not high with a CLC filter.

Take your pick. There are no free rides while using simpler topologies.
A relatively easy way out would be a SS filter/regulator. I favor things
like the Int. Rectifier FETs to do the work.

People have been using CLC filters with no sonic problems for years
without
resorting to solid state regulators, which always do result in a power
loss, because of the voltage drop x load current across the series
pass element, or the B+ voltage x shunt element in the case of a shunt
regulator.

Regulators done with SS power fets or well rated bjt like the BU208 waste
power,
CLC filters don't, because of the insignificant power lost
in the dcR of the choke, which totals Idc squared x R, in watts.


Good Luck with your project, John Stewart

I don't think the original poster's luck
will be improved by erroneous advice.

Patrick Turner.

Nowhere did I ever suggest all the values for the CLC filter shown in the
test schematic at your post at ABSE.

You mean like this,? posted by Patrick Turner on 10/20/2004?

For example, I have a solid state amp I am rebuilding,
and I have 65 vrms from the mains tranny,
and I plan to use solid state rectifiers, 250 mH chokes, and 10,000 uF
caps on the rails.
The idle load is about 200 ohms.

I believe this is what JH was describing, but a little inaccurately.

We have some way to go before reaching the 20th month of 2004.

The God Of Triodes may issue all of us a spare extra 8 mths,
which I need to get through the work I have, but only if we don't misbehave.

Patrick Turner.

Patrick Turner wrote:

John Stewart wrote:

lazyadm1n wrote:

Not to open a bag of worms or anything, but what (if any) are the
advantages/disadvanteges of a CRC filter vs a CLC filter in a power supply?

Asides from the higher cost and larger size of a choke, is there any reason
to choose one over the other?

One more question about chokes has to do with sizing. How does one determine
what size choke to use?
_________________
Rod

www.dortoh.ca

With the CLC filter there will be a resonance, possibly in the AF range.
I used Patrick's proposed values in this simulation. See the results at ABSE.

Nowhere did I ever suggest all the values for the CLC filter shown in the
test schematic at your post at ABSE.

The post was not meant to criticize your choice of components for the filter
or to embarrass you. I simply used the values which happened to be in the
discussion. I could just as easily chosen any number of other sets of values.

The values you posted to gain the results for resonance were :-

PS generator resistance = 1kOhm,
C1 = 10mF, which is milli Farads, or 10,000uF,
L = 250 milli Henrys.
C2 = 10mF, which is milli Farads, or 10,000 uF,
RL = 200 ohms.
I assume your model used the questionable Duncan Amps freely
downloadable power supply designer program which I found gave me some
incomprehensible results.

Not at all. I have not tried the software you refer too, nor have I bothered to
download it from the net. I have been using a version of Electronic Workbench
for a few years now & find it to be quite accurate.

The schematic you posted is misleading to those who
may think that 10mF = 10 uF!!!!!!

I am certainly aware of the difference between a milli & a micro.
The simulation uses caps of 10 millifarads.

I recall the discussions revolved around a
very low generator impedance, ie, a large SS amp
power tranny feeding through SS diodes into an LC filter,
with approx 250 mH and 10,000 uF.

Fo = 3.18 Hz.

I have redrawn the simple schema so that anyone can see that
the circuit is parallel resonant at 4.505 Hz & included the formula.
The caps are in series so far as the circuit is concerned. If there
are any doubters it is easy to hook up a test circuit to try on
the bench. The resonance resulting in each case is quite obvious.

The 200 ohms is not low enough to damp the LC resonance,
but for critical damping, 7 ohms is required, so the 1.0 ohm dcR of the choke
effectively in series with the L will still leave the Q of the filter somewhat
higher than desirable,
but I found the voltage stability at the 10,000 uF didn't bounce around
when intermittently shunting the 200 ohm bleeder R with 32 ohms.

If the DCR of the choke is One Ohm I can add that in later. If you have
the ESR of the caps we can add that into the simulation as well.

For now go to ABSE to see the filter redrawn.

Cheers, John Stewart

John Stewart wrote:

Patrick Turner wrote:

John Stewart wrote:

lazyadm1n wrote:

Not to open a bag of worms or anything, but what (if any) are the
advantages/disadvanteges of a CRC filter vs a CLC filter in a power supply?

Asides from the higher cost and larger size of a choke, is there any reason
to choose one over the other?

One more question about chokes has to do with sizing. How does one determine
what size choke to use?
_________________
Rod

www.dortoh.ca

With the CLC filter there will be a resonance, possibly in the AF range.
I used Patrick's proposed values in this simulation. See the results at ABSE.

Nowhere did I ever suggest all the values for the CLC filter shown in the
test schematic at your post at ABSE.

The post was not meant to criticize your choice of components for the filter
or to embarrass you. I simply used the values which happened to be in the
discussion. I could just as easily chosen any number of other sets of values.

But the choice of values just happened to be extraordinarily similar to what I had
chosen.
Then you appeared to use this choice to support the general idea that CLC filters were

poor engineering.





The values you posted to gain the results for resonance were :-

PS generator resistance = 1kOhm,
C1 = 10mF, which is milli Farads, or 10,000uF,
L = 250 milli Henrys.
C2 = 10mF, which is milli Farads, or 10,000 uF,
RL = 200 ohms.
I assume your model used the questionable Duncan Amps freely
downloadable power supply designer program which I found gave me some
incomprehensible results.

Not at all. I have not tried the software you refer too, nor have I bothered to
download it from the net.

Duncan amps presents the circuit in an almost identical fashion.

But in a power supply, who would ever have
such a filter?

Why on earth would there be 1 kohm of series R between a voltage source
and C1?

Why isn't the power supply represented by a low impedance with diodes and
providing a DC flow, which affects the way the choke works, and its inductance value.

To newbies, the post of yous could be very confusing.


I have been using a version of Electronic Workbench
for a few years now & find it to be quite accurate.

Fair enough.
I found Duncan's software a bit plain wrong in its
depictions of the C2 voltage after turn on with an LC input,
but never mind, that's a separate issue on which nobody has commented after I raised
it.



The schematic you posted is misleading to those who
may think that 10mF = 10 uF!!!!!!

I am certainly aware of the difference between a milli & a micro.
The simulation uses caps of 10 millifarads.

Yes, I just reminded everyone, lest they are bewildered from
the times when where 10 mF meant 10 uF.



I recall the discussions revolved around a
very low generator impedance, ie, a large SS amp
power tranny feeding through SS diodes into an LC filter,
with approx 250 mH and 10,000 uF.

Fo = 3.18 Hz.

I have redrawn the simple schema so that anyone can see that
the circuit is parallel resonant at 4.505 Hz & included the formula.
The caps are in series so far as the circuit is concerned.

Indeed, because of the large value of series R before C1,
the CLC behaves as a sub optimally terminated low pass filter,
about as useful as tits on a bull for anyone designing and building a tube or SS amp.

General conclusions about CLC in power supplies cannot be realized from the
circuit you have posted.

are any doubters it is easy to hook up a test circuit to try on
the bench. The resonance resulting in each case is quite obvious.

So what?

Nobody in their right mind would use your circuit, they'd just be confused by it.





The 200 ohms is not low enough to damp the LC resonance,
but for critical damping, 7 ohms is required, so the 1.0 ohm dcR of the choke
effectively in series with the L will still leave the Q of the filter somewhat
higher than desirable,
but I found the voltage stability at the 10,000 uF didn't bounce around
when intermittently shunting the 200 ohm bleeder R with 32 ohms.

If the DCR of the choke is One Ohm I can add that in later. If you have
the ESR of the caps we can add that into the simulation as well.

My post on the other hand specifically relates the CLC behaviour to real world
situations and conditions,
and is not theory with ill fitting conclusions and recomendations attached.

I went to some length to address the issue of the importance of resistance
damping of LC filter circuits to avoid the problems of unwanted peaks in their
voltage output.

An LC filter when driven from a low resistance source
but with no R component either across the C, or across the L,
or in series before the LC to the source,
will produce a very peaked response at the C, at Fo depending on the
dcR of the L.

To make the filter have no resonant peak, but achieve
a -3 dB attenuation at Fo, and a following attenuation slope of 12dB /octave,
you need to have Rsource = very low, and have dcR = very low,
and then have at least an R across the C ( etc) = 1.41 x ZC or ZL at Fo.

1.41 x ZC or ZL is regarded as the critical value of R for damping an LC
circuit for "maximum flatness" of the response.

At Fo, ZC = ZL.

Now if R = some lower value than Rcrit, then the response slope will be what is called

over damped, and the roundness of the shoulder of the attenuation less sharp,
with the -3 dB point at a lower F, but the filter will still have a 12 dB/octave slope

at 3 Fo and beyond.

This sort of over damped LC is not used in PS, but is useful in
speaker crossovers.

As the R is made higher than Rcrit, the response of the filter becomes non flat,
and a peak appears around Fo, becoming a high peak maybe 15 dB above the LF input
level to the filter.

Its important that students studying such things be fully aware of such behaviours,
and get off their bums, away from the PC, and into the workshop
to examine some real world LC behaviours.
For those wondering about the relevance of this discussion,
I suggest they study the behaviour of CLC low pass filters and their
interactions with R attatched at the input and output, and be prepared for
what seem to be some very odd non-common sense behaviour.


For now go to ABSE to see the filter redrawn.

Its precisely no different to the previous circuit, but yes,
you effectively have a 5,000 uF plus 250 mH in a circuit in which
the resonant F is 4.5 Hz.



A useful formula for resonance is

Fo = 5,035 / sq rt of ( C x L ),

where F is in Hertz,
C is in uF,
L is in milli Henrys.

From this we can derive any value of L or C to make a
a resonant if we know the value of one of the L&C components.

When I searched for a decent LC filter program on the Web
for all types of lpf, hpf, band stop f , band pass f, notch f etc, using passive
components,
the only freeware i could find was at

http://www-users.cs.york.ac.uk/~fisher/lcfilter/

This doesn't allow you to cobble anything you like to together and find out
what the response is; you must specify typical input and output impedances
which are generally similar.

So its not a very useful resource, because with many filter apps, we start with a low
Z signal source
such as a power tranny, or a cathode follower and don't want to have to have a low
impedance on the
output, or adversely load the source impedance.

afaik, there are not many free downloadable LC filter programs which are worth
the trouble of downloading.

Perhaps someone may correct me on that.



Cheers, John Stewart

Patrick Turner wrote:


With the CLC filter there will be a resonance, possibly in the AF range.
I used Patrick's proposed values in this simulation. See the results at ABSE.

Nowhere did I ever suggest all the values for the CLC filter shown in the
test schematic at your post at ABSE.

The post was not meant to criticize your choice of components for the filter
or to embarrass you. I simply used the values which happened to be in the
discussion. I could just as easily chosen any number of other sets of values.

But the choice of values just happened to be extraordinarily similar to what I had
chosen.

Not only that, they are the same & I said so somewhere in my post.

Then you appeared to use this choice to support the general idea that CLC filters were
poor engineering.

Not at all. As usual you are jumping to conclusions. I am detecting insecurity here.

The values you posted to gain the results for resonance were :-

PS generator resistance = 1kOhm,
C1 = 10mF, which is milli Farads, or 10,000uF,
L = 250 milli Henrys.
C2 = 10mF, which is milli Farads, or 10,000 uF,
RL = 200 ohms.

You got that correct, anyway.

I assume your model used the questionable Duncan Amps freely

downloadable power supply designer program which I found gave me some
incomprehensible results.

Not at all. I have not tried the software you refer too, nor have I bothered to
download it from the net.

Duncan amps presents the circuit in an almost identical fashion.

But in a power supply, who would ever have
such a filter?

You, I & many others.

Why on earth would there be 1 kohm of series R between a voltage source
and C1?

You are having a problem of understanding the difference between a real circuit
& a short cut for simulation only. The simulation is to demonstrate resonance.
Don't worry to much, it will happen in a real circuit anyway.

Why isn't the power supply represented by a low impedance with diodes and
providing a DC flow, which affects the way the choke works, and its inductance value.

Yes, but it is low Z only while the diodes are conducting at the rectifier end of the
filter. The load end can oscillate all over depending on load changes & it does.
Swinging chokes were once popular with the Class B set. They are no longer
shown in the Hammond catalogue. The choke I used for my tests below changes
about 20% from no load to full load.

To newbies, the post of yous could be very confusing.

If you go to ABSE you will see a result measured today on a real circuit.
The filter is a PI of a pair of 20 microfarad caps & a Hammond 10 H
choke. The choke resistance is 82 ohms. It is in a regulated PS but just as
easily could have been seen in an amp of the 50's. The 40 volt jumps
are caused by a 70 ma change, first on then off. The trace demonstrates
well what I tried to make others aware of before you got bent out of shape.

It's time you listened a bit to the advice of others.

If I have time later this week I will post some stuff on what happens to
the filter in an SE amp.

Cheers to all, John Stewart

Patrick Turner wrote in message ...
John Stewart wrote:

lazyadm1n wrote:

Not to open a bag of worms or anything, but what (if any) are the
advantages/disadvanteges of a CRC filter vs a CLC filter in a power supply?

the worms are everywhere now.


The values you posted to gain the results for resonance were :-

PS generator resistance = 1kOhm,

whats a PS generator?

C1 = 10mF, which is milli Farads, or 10,000uF,
L = 250 milli Henrys.
C2 = 10mF, which is milli Farads, or 10,000 uF,
RL = 200 ohms.
I assume your model used the questionable Duncan Amps freely
downloadable power supply designer program which I found gave me some
incomprehensible results.

The schematic you posted is misleading to those who
may think that 10mF = 10 uF!!!!!!

it is. Lots of uF caps are marked mF. Always puzzles newbies. If your
software treats mF as = 1000uF, its a bit odd.


In the case of an LC filter, any resonance of the LC circuit
is damped when the value of the inductance changes considerably
with a varying charge rate into the C.

really? how do you reach that conclusion?


In my case with the LC filters for this SS amp,
the tested L for a 250 ohm load with a +55v rail was 0.35 H, or 350 mH.
When 32 ohms was added to the 250 ohms for total 28 ohms,
Idc became 1.9 amps dc, and L became 0.12 H, or 120 mH.

But the test circuit showed no sign of wild resonance voltage swings.
if there were, the choke goes from being higher L to a low value and which
saturates
for part of the rectifier wave forms, and becomes a very much lower
value of L when it does, so resonance seems damped
since L does not stay at a constant value.

I'm wondering how that would damp resonance.


The amp in question will be used as a sub amp, but will still have
input filtering to give a pole at 10 Hz.

I still don't believe the resonance will affect the sound one iota.

The resonance appears at about 4.5 Hz. This will have some effect
on the amp's sound.

There may be some amps which have a resonance in the CLC filter,
or LC filter ot CLCLC filter which may be at just under 5 Hz.

In none of them have I found there is any audible artifact.

This is fundamental theory. No output stage has perfect PS rejection,
therefore psu gunk will cause atrifacts on the output. Inevitably.


In a PP amp, any 5 Hz ripples are applied to the CT and common mode
rejection prevents their appearance in the output signal.

Rejection is never perfect. Look at some transistor curves and see
what happens as you vary Vce.


But even in SE amps, I sure don't get such problems in my amps.

there is no way for you not to.


I have always recommended the use of very large value C2 in a CLC
filter of a tube amp, 470 uF being typical.

which will certainly help.


This class A amp has an OPT, and CR coupling, like a tube amp,
and the circuit has a total of 20 dB of NFB,
and there is no resonance problems at LF whatever,
or stability problems because
the circuit open loop gain is well below unity where the LF phase shift
is 180 degrees.

what happens at 90 degrees determines stability.


On the other hand the CRC filter response is smooth but the power
losses are high.

The power losses are low, not high with a CLC filter.

Take your pick. There are no free rides while using simpler topologies.
A relatively easy way out would be a SS filter/regulator. I favor things
like the Int. Rectifier FETs to do the work.

People have been using CLC filters with no sonic problems for years

incorrect.


without
resorting to solid state regulators, which always do result in a power
loss, because of the voltage drop x load current across the series
pass element, or the B+ voltage x shunt element in the case of a shunt regulator.

yes, thats the price of better kit. (I cant imagine any grown up
designer using a shunt reg though.)


Regulators done with SS power fets or well rated bjt like the BU208 waste power,
CLC filters don't, because of the insignificant power lost
in the dcR of the choke, which totals Idc squared x R, in watts.


Good Luck with your project, John Stewart

I don't think the original poster's luck
will be improved by erroneous advice.

You either cant work out what you dont know, or are determined to
maintain an Uberexpert image to sell your goods. I'm sure you know
enough to make some fairly nice amps, but they wont be the best by any
means. If you read up on power supply rejection, transformer
regulation and ss reg design you'd produce some much better kit.


NT

"N. Thornton" wrote:

Patrick Turner wrote in message ...
John Stewart wrote:

lazyadm1n wrote:

Not to open a bag of worms or anything, but what (if any) are the
advantages/disadvanteges of a CRC filter vs a CLC filter in a power supply?

the worms are everywhere now.

The values you posted to gain the results for resonance were :-

PS generator resistance = 1kOhm,

whats a PS generator?

C1 = 10mF, which is milli Farads, or 10,000uF,
L = 250 milli Henrys.
C2 = 10mF, which is milli Farads, or 10,000 uF,
RL = 200 ohms.
I assume your model used the questionable Duncan Amps freely
downloadable power supply designer program which I found gave me some
incomprehensible results.

The schematic you posted is misleading to those who
may think that 10mF = 10 uF!!!!!!

it is. Lots of uF caps are marked mF. Always puzzles newbies. If your
software treats mF as = 1000uF, its a bit odd.

In the case of an LC filter, any resonance of the LC circuit
is damped when the value of the inductance changes considerably
with a varying charge rate into the C.

really? how do you reach that conclusion?

You obviously have not carefully observed the "swinging choke"
inductance value with varying power levels going into the amp circuit.
I described it in detail in my posts here.



In my case with the LC filters for this SS amp,
the tested L for a 250 ohm load with a +55v rail was 0.35 H, or 350 mH.
When 32 ohms was added to the 250 ohms for total 28 ohms,
Idc became 1.9 amps dc, and L became 0.12 H, or 120 mH.

But the test circuit showed no sign of wild resonance voltage swings.
if there were, the choke goes from being higher L to a low value and which
saturates
for part of the rectifier wave forms, and becomes a very much lower
value of L when it does, so resonance seems damped
since L does not stay at a constant value.

I'm wondering how that would damp resonance.

The Fo changes with a changing L value, so little resonance occurs.
For resonance, you need a fixed value for L and C, and the Q
of the LC circuit must be high....

I suggest you build a few PS, and observe, observe....



The amp in question will be used as a sub amp, but will still have
input filtering to give a pole at 10 Hz.

I still don't believe the resonance will affect the sound one iota.

The resonance appears at about 4.5 Hz. This will have some effect
on the amp's sound.

There may be some amps which have a resonance in the CLC filter,
or LC filter ot CLCLC filter which may be at just under 5 Hz.

In none of them have I found there is any audible artifact.

This is fundamental theory. No output stage has perfect PS rejection,
therefore psu gunk will cause atrifacts on the output. Inevitably.

But the unresolved gunk you speak of is a lot less than noise and distortions from
other sources.
Even with the Quad II attrociously inadequate PS, the IM distortion caused by
the PS is about the same as the THD levels of the amps.
With an improved CLC plate supply, the IM from PS is reduced about 30 dB at least.

And Quad II at 2 watt normal listening levels make only about 0.03%
thd when in stock standard form.



In a PP amp, any 5 Hz ripples are applied to the CT and common mode
rejection prevents their appearance in the output signal.

Rejection is never perfect. Look at some transistor curves and see
what happens as you vary Vce.

All the more reason to filter out the hum on transistor collector
circuit rails, achievable just LC, or CLC, where C1 is say 5,000
uF, and C2 is a far higher value, with a low dcR choke from C1 to C2.

There is then little dependance on NFB to remove noise in the SS amp output.
So less NFB need be used, or if a lot is used, its more effective.


But even in SE amps, I sure don't get such problems in my amps.

there is no way for you not to.

What bull****. The levels of PS caused spuriae
in at the output of all my SE amps is inaudible, and measures far less
than the natural thd/imd of the signal processing, at all levels of operation.




I have always recommended the use of very large value C2 in a CLC
filter of a tube amp, 470 uF being typical.

which will certainly help.

This class A amp has an OPT, and CR coupling, like a tube amp,
and the circuit has a total of 20 dB of NFB,
and there is no resonance problems at LF whatever,
or stability problems because
the circuit open loop gain is well below unity where the LF phase shift
is 180 degrees.

what happens at 90 degrees determines stability.

Er, you need 180 degrees of phase shift for instability.

But lets not argue about a few degrees.



On the other hand the CRC filter response is smooth but the power
losses are high.

The power losses are low, not high with a CLC filter.

Take your pick. There are no free rides while using simpler topologies.
A relatively easy way out would be a SS filter/regulator. I favor things
like the Int. Rectifier FETs to do the work.

People have been using CLC filters with no sonic problems for years

incorrect.

Well you are very inexperienced.



without
resorting to solid state regulators, which always do result in a power
loss, because of the voltage drop x load current across the series
pass element, or the B+ voltage x shunt element in the case of a shunt regulator.

yes, thats the price of better kit. (I cant imagine any grown up
designer using a shunt reg though.)

I can imagine a grown up using a shunt reg.



Regulators done with SS power fets or well rated bjt like the BU208 waste power,
CLC filters don't, because of the insignificant power lost
in the dcR of the choke, which totals Idc squared x R, in watts.


Good Luck with your project, John Stewart

I don't think the original poster's luck
will be improved by erroneous advice.

You either cant work out what you dont know, or are determined to
maintain an Uberexpert image to sell your goods. I'm sure you know
enough to make some fairly nice amps, but they wont be the best by any
means. If you read up on power supply rejection, transformer
regulation and ss reg design you'd produce some much better kit.

And what do you produce and sell?

Complex junk riddled with SS crap all through the circuit?

I have compared the sound of my gear at audiophile meetings
with examples of high end with all their complex and very unreliable
SS regs, and recieved very favourable reports.

You are one of the crowd who bases his judgements of "bestness"
on measured results.

That being the case, get off this group, you don't belong, you waste out time,
and your own, because well all know an SS amp can measure
at 0.0001% thd at 200 watts, but frankly, we don't hear any difference if we remove
two zeros from the figures.

To conclude, there is no evidence that well designed CLC
filters in tube gear will ever contribute more than 10% of the total measured
N&D of the amps concerned, and if that is say 0.03% as it is with most
of my amps at normal levels, then the N&D contribution from my PSUs is
a mere 0.003% of the signal.

If the signal level is 4 vrms at the 8 ohm speaker, the
level of the PSU caused N&D at 0.003% is only 0.012 mV.

If you wanna come back with some figures to support the idea that
well designed CLC are ****e in amplifiers, then do so,
but you better get your facts well sorted out.

Patrick Turner.

Patrick Turner wrote in message ...
"N. Thornton" wrote:
John Stewart wrote:
lazyadm1n wrote:

PS generator resistance = 1kOhm,

whats a PS generator?

C1 = 10mF, which is milli Farads, or 10,000uF,
L = 250 milli Henrys.
C2 = 10mF, which is milli Farads, or 10,000 uF,
RL = 200 ohms.
I assume your model used the questionable Duncan Amps freely
downloadable power supply designer program which I found gave me some
incomprehensible results.

The schematic you posted is misleading to those who
may think that 10mF = 10 uF!!!!!!

it is. Lots of uF caps are marked mF. Always puzzles newbies. If your
software treats mF as = 1000uF, its a bit odd.

In the case of an LC filter, any resonance of the LC circuit
is damped when the value of the inductance changes considerably
with a varying charge rate into the C.

really? how do you reach that conclusion?

You obviously have not carefully observed the "swinging choke"
inductance value with varying power levels going into the amp circuit.
I described it in detail in my posts here.

A silly comment. The changing L of a swinging choke does not kill
resonance, it merely moves it about frequency wise.


In my case with the LC filters for this SS amp,
the tested L for a 250 ohm load with a +55v rail was 0.35 H, or 350 mH.
When 32 ohms was added to the 250 ohms for total 28 ohms,
Idc became 1.9 amps dc, and L became 0.12 H, or 120 mH.

But the test circuit showed no sign of wild resonance voltage swings.
if there were, the choke goes from being higher L to a low value and which
saturates
for part of the rectifier wave forms, and becomes a very much lower
value of L when it does, so resonance seems damped
since L does not stay at a constant value.

I'm wondering how that would damp resonance.

The Fo changes with a changing L value, so little resonance occurs.

non sequitor

For resonance, you need a fixed value for L and C, and the Q
of the LC circuit must be high....

nope.


I suggest you build a few PS, and observe, observe....

posing


There may be some amps which have a resonance in the CLC filter,
or LC filter ot CLCLC filter which may be at just under 5 Hz.

In none of them have I found there is any audible artifact.

This is fundamental theory. No output stage has perfect PS rejection,
therefore psu gunk will cause atrifacts on the output. Inevitably.

But the unresolved gunk you speak of is a lot less than noise and distortions from
other sources.
Even with the Quad II attrociously inadequate PS, the IM distortion caused by
the PS is about the same as the THD levels of the amps.
With an improved CLC plate supply, the IM from PS is reduced about 30 dB at least.

And Quad II at 2 watt normal listening levels make only about 0.03%
thd when in stock standard form.


But even in SE amps, I sure don't get such problems in my amps.

there is no way for you not to.

What bull****. The levels of PS caused spuriae
in at the output of all my SE amps is inaudible, and measures far less
than the natural thd/imd of the signal processing, at all levels of operation.

you say inaudible, i say inevitable.


I have always recommended the use of very large value C2 in a CLC
filter of a tube amp, 470 uF being typical.

which will certainly help.

This class A amp has an OPT, and CR coupling, like a tube amp,
and the circuit has a total of 20 dB of NFB,
and there is no resonance problems at LF whatever,
or stability problems because
the circuit open loop gain is well below unity where the LF phase shift
is 180 degrees.

what happens at 90 degrees determines stability.

Er, you need 180 degrees of phase shift for instability.

wrong. Anything from 90 degs to 270 can do it with the right gain.
Think about this: lets say phase shift is 179 degs, and gain 2. You
draw those 2 cycles superimposed on paper, and try tell me it wont
oscillate.


But lets not argue about a few degrees.


without
resorting to solid state regulators, which always do result in a power
loss, because of the voltage drop x load current across the series
pass element, or the B+ voltage x shunt element in the case of a shunt regulator.

yes, thats the price of better kit. (I cant imagine any grown up
designer using a shunt reg though.)

I can imagine a grown up using a shunt reg.

in an amp psu? I cant. Senseless idea.


You either cant work out what you dont know, or are determined to
maintain an Uberexpert image to sell your goods. I'm sure you know
enough to make some fairly nice amps, but they wont be the best by any
means. If you read up on power supply rejection, transformer
regulation and ss reg design you'd produce some much better kit.

And what do you produce and sell?

Complex junk riddled with SS crap all through the circuit?

I have compared the sound of my gear at audiophile meetings
with examples of high end with all their complex and very unreliable
SS regs, and recieved very favourable reports.

thats to be expected, again do some reading on subjective tests.


You are one of the crowd who bases his judgements of "bestness"
on measured results.

nope


If you wanna come back with some figures to support the idea that
well designed CLC are ****e in amplifiers, then do so,

not what i claimed. And no thanks, ive no interest in educating
someone not interested in learning.


NT