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Chris Hornbeck Chris Hornbeck is offline
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Default On the origin and workings of "Fast" Power supplies

On 12 Dec 2006 19:21:20 -0800, "Bret Ludwig"
wrote:

Use the relay to short the output to ground, rather than open it. The
power amp should have circuitry that protects it from running into a
dead short. If THAT fails, better to blow up the output transistors
than a potentially $10K+ speaker system


Crowbars, including solid-state ones using SCR's, have
been used since the 1970's, for example, the McIntosh
MA6100.

They do have their limitations, as you've noted, and
their advantages. To take advantage of crowbars, the
designer must integrate them with a slow-start regimen
to prevent turn-on transients (under *all* conditions)
and with a soft turn-off (under *all* conditions).

Do-able, obviously, but not trivial. For critical use,
the contact resistance of a relay idling for years(?)
is too problematical, so it's never done.

All good fortune,

Chris Hornbeck
"Too soon oldt; too late schmardt."
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Arny Krueger Arny Krueger is offline
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Default "Fast" Power supplies

"flipper" wrote in message

On Tue, 12 Dec 2006 18:18:54 -0500, "Arny Krueger"
wrote:

"flipper" wrote in message


A passive component can cause nonlinear distortion - a
good example would be a diode.


Of course. So can a transformer and, as that article
shows, a capacitor.


However, if the distortion only arises under operational
conditions that never arise in typical use, then it is
irrelevant.



It was relevant to the topic, as was explained in what
you snipped out as a prerequisite to making that
supercilious comment.


My comment was precipitated by the fact that you tried to introduce
irrelevant information, and then declined to take responsbility for that
act.


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Arny Krueger Arny Krueger is offline
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Default On the origin and workings of "Fast" Power supplies

"Chris Hornbeck" wrote in
message news
On 12 Dec 2006 19:21:20 -0800, "Bret Ludwig"
wrote:

Use the relay to short the output to ground, rather than
open it. The power amp should have circuitry that
protects it from running into a dead short. If THAT
fails, better to blow up the output transistors than a
potentially $10K+ speaker system


Crowbars, including solid-state ones using SCR's, have
been used since the 1970's, for example, the McIntosh
MA6100.

They do have their limitations, as you've noted, and
their advantages. To take advantage of crowbars, the
designer must integrate them with a slow-start regimen
to prevent turn-on transients (under *all* conditions)
and with a soft turn-off (under *all* conditions).

Do-able, obviously, but not trivial. For critical use,
the contact resistance of a relay idling for years(?)
is too problematical, so it's never done.


Dry-contact relays with sealed contacts (e.g. reed relays) or
current-handling relays with self-wiping contacts made of reasonable
materials, are extremely reliable. They just take a little care to properly
specify, and a little money to obtain.


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Ruud Broens Ruud Broens is offline
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Default "Fast" Power supplies


"Eeyore" wrote in message
...
:
:
: Ruud Broens wrote:
:
: "Eeyore" wrote in message
: : Ruud Broens wrote:
:
: : :
: : ...opinions you get to have :-)
: : i've kept an eye on B&W over the years, as they've repeatedly used the
same
: : design considerations i used in my diy speakers - that inspires
confidence
: :-)
: : alas, haven't yet heard the 802D's, yet
: :
: : Do they use driver impedance correction ?
: :
: : Graham
: :
: nah, they bought some guitar speakers from a surplus outlet,
: glued 'm into a cardboard box, threw in some parts from the
: junk bin for good measure and
: that's about it
:
: Ah - you're a funny man too.
:
: Let me guess.... You really don't know but felt obliged to say something daft
: anyway ?

just to give you an idea of how silly your line of questioning is,
consider eg. DIY magazines like Hobby Hifi, a german bimonthly,
where the Kit Pro 17.5 2 way is presented
...Audax Aerogel low/mid, Bohlender magnetostat tweeter
the developer, Rainer Kroenke, has one of the largest
'quiet rooms' in industry, he used B&Kj equipment,
MLSSA , the works
final result:
50Hz - 15kHz on axis virtually flat fr,

measurement data on the Bohlender-Graebener Neo 3 PDR-W/FPtweeter
MLSSA waterfall diagram over nearly all of 400 Hz/40 kHz
dead as a doormat in 1 ms *some worst case 2ms around
minor resonances in the tweeter 2-3 kHz, formidable indeed

data, measured for the Audax HM 170 MNO
very good cascading waterfall spectrum, matching
the tweeter at around 2.5 kHz, fortunately enabling
crossover freq there

crossover fixes some minor details and uses
Mundorf caps

oohh, impedance correction was implemented in the filter
of this 250 euro/speaker project, as well :-)

Rudy
somewhat better informed


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Ruud Broens Ruud Broens is offline
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Default "Fast" Power supplies


"Ruud Broens" wrote in message
...
:
: "Eeyore" wrote in message
: ...
: :

...DIY magazines like Hobby Hifi, a german bimonthly,

: where the Kit Pro 17.5 2 way is presented
: ..Audax Aerogel low/mid, Bohlender magnetostat tweeter
: the developer, Rainer Kroenke, has one of the largest
: 'quiet rooms' in industry, he used B&Kj equipment,
: MLSSA , the works
: final result:
: 50Hz - 15kHz on axis virtually flat fr,
:
: measurement data on the Bohlender-Graebener Neo 3 PDR-W/FPtweeter
: MLSSA waterfall diagram over nearly all of 400 Hz/40 kHz
: dead as a doormat in 1 ms *some worst case 2ms around
: minor resonances in the tweeter 2-3 kHz, formidable indeed
:
: data, measured for the Audax HM 170 MNO
: very good cascading waterfall spectrum, matching
: the tweeter at around 2.5 kHz, fortunately enabling
: crossover freq there
:
: crossover fixes some minor details and uses
: Mundorf caps
:
: oohh, impedance correction was implemented in the filter
: of this 250 euro/speaker project, as well :-)
:
: Rudy
: somewhat better informed
:
see he
http://www.hobbyhifi.de/Aktuell/Aktu...e_ausgabe.html

(if you're serious about speakers, learn to read German!
the above lines being a condensation of a 9 page article,
lot's of graphs, construction plan & notes ...the usual German
gruendlichkeit, eh :-)
R.




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Andy Evans Andy Evans is offline
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Default On the origin and workings of "Fast" Power supplies


Eeyore wrote:
"Bob H." wrote:

No , they don't need a speaker *DC* protection.

IME, the relays needed for speaker protection of
direct-coupled amplifiers, have, over the service
life of good equipment, *more* of a sonic penalty
and much more of a reliability penalty than a
good transformer. And that's saying a lot.


How about just using a high grade audio cap instead of the relay?
If you want to get serious, a large film cap?


The whole raison d'etre of DC coupled amps is to get rid of that cap.

2000uf polypropylene btw ?

Graham


You say that, but I do have one 470uF polypropylene. Four of those? You
may ask if they are big...........

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Bob H. Bob H. is offline
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Default On the origin and workings of "Fast" Power supplies


Bob H. wrote:
Eeyore wrote:

2000uf polypropylene btw ?

Graham


MY Harmon Kardon uses a 100uf cap, and it's the only one in the signal
chain. Since it's my only SS amp, it's what I'm familiar with. And I
will be replacing them with at least Silmacs, and probably foil caps
when I get around to it.


Actually, I think it's 1000uf, and yes it's the coupling cap to the
speakers. I remember a factor of 10. I'll check the schematic again
when I get home. But how about 1 or 2kuf silmac or similar, bypassed
by a 100 or 50uf film?

Does anyone build low voltage foil caps? (lower than speaker caps).
They could be wound with thinner film, for smaller size, and for SS,
much lower voltages are needed.

Bob H.

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Eeyore Eeyore is offline
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Default On the origin and workings of "Fast" Power supplies



"Bob H." wrote:

Bob H. wrote:
Eeyore wrote:

2000uf polypropylene btw ?

Graham


MY Harmon Kardon uses a 100uf cap, and it's the only one in the signal
chain. Since it's my only SS amp, it's what I'm familiar with. And I
will be replacing them with at least Silmacs, and probably foil caps
when I get around to it.


Actually, I think it's 1000uf, and yes it's the coupling cap to the
speakers. I remember a factor of 10. I'll check the schematic again
when I get home. But how about 1 or 2kuf silmac or similar, bypassed
by a 100 or 50uf film?


Is this a 'single supply' amplifier design ?

The idea of bypassing is yet more unfounded nonsense btw.

I'm not sure what the great idea's supposed to be with silk included in the
dielectric. I'd use a modern low-ESR design. It'll help to use a larger value
too like the 2000 uF I mentioned.


Does anyone build low voltage foil caps? (lower than speaker caps).
They could be wound with thinner film, for smaller size, and for SS,
much lower voltages are needed.


The lowest voltage film caps I've normally seen are 50V. There's a limit to how
thin the film can be made reliably.

Graham

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Ruud Broens Ruud Broens is offline
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Default On the origin and workings of "Fast" Power supplies


"Eeyore" wrote in message
...
:
:
: "Bob H." wrote:
:
: Bob H. wrote:
: Eeyore wrote:
:
: 2000uf polypropylene btw ?
:
: Graham
:
: MY Harmon Kardon uses a 100uf cap, and it's the only one in the signal
: chain. Since it's my only SS amp, it's what I'm familiar with. And I
: will be replacing them with at least Silmacs, and probably foil caps
: when I get around to it.
:
: Actually, I think it's 1000uf, and yes it's the coupling cap to the
: speakers. I remember a factor of 10. I'll check the schematic again
: when I get home. But how about 1 or 2kuf silmac or similar, bypassed
: by a 100 or 50uf film?
:
: Is this a 'single supply' amplifier design ?
:
: The idea of bypassing is yet more unfounded nonsense btw.
:
: I'm not sure what the great idea's supposed to be with silk included in the
: dielectric. I'd use a modern low-ESR design. It'll help to use a larger value
: too like the 2000 uF I mentioned.
:
:
: Does anyone build low voltage foil caps? (lower than speaker caps).
: They could be wound with thinner film, for smaller size, and for SS,
: much lower voltages are needed.
:
: The lowest voltage film caps I've normally seen are 50V. There's a limit to how
: thin the film can be made reliably.
:
: Graham

a modern stacked polyprop can easily have some 2500 layers.
as the thickness of the metallic layer can be neglected, a 10 mm
tall stack makes for a 4 um dielectric thickness. the odd and even
layers are end connected by what is called the Schoops process.
quite advanced manufacturing at work :-)
50V across 4 um is like 12 KV/mm, so limits are imposed by the
dielectric's punch through capability

Rudy


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Bob H. Bob H. is offline
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Default On the origin and workings of "Fast" Power supplies



MY Harmon Kardon uses a 100uf cap, and it's the only one in the signal
chain. Since it's my only SS amp, it's what I'm familiar with. And I
will be replacing them with at least Silmacs, and probably foil caps
when I get around to it.


My mistake. The 100uf caps are at the input of the amp section. The
ouputs are direct coupled. It's been a couple of years since I looked
at the schematic, and just made a mental note to look into alternatives
for those caps.

Bob H.



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Eeyore Eeyore is offline
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Default On the origin and workings of "Fast" Power supplies



"Bob H." wrote:

MY Harmon Kardon uses a 100uf cap, and it's the only one in the signal
chain. Since it's my only SS amp, it's what I'm familiar with. And I
will be replacing them with at least Silmacs, and probably foil caps
when I get around to it.


My mistake. The 100uf caps are at the input of the amp section. The
ouputs are direct coupled. It's been a couple of years since I looked
at the schematic, and just made a mental note to look into alternatives
for those caps.


Is it in the feedback loop by any chance ?

Graham

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Sander deWaal Sander deWaal is offline
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Default On the origin and workings of "Fast" Power supplies

Eeyore said:


MY Harmon Kardon uses a 100uf cap, and it's the only one in the signal
chain. Since it's my only SS amp, it's what I'm familiar with. And I
will be replacing them with at least Silmacs, and probably foil caps
when I get around to it.



My mistake. The 100uf caps are at the input of the amp section. The
ouputs are direct coupled. It's been a couple of years since I looked
at the schematic, and just made a mental note to look into alternatives
for those caps.



Is it in the feedback loop by any chance ?



A DC-blocking cap at the input?
Not likely.


--
- Ever seen someone with 5.1 ears? So, what does that tell you? -
  #173   Report Post  
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Bob H. Bob H. is offline
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Default On the origin and workings of "Fast" Power supplies


Sander deWaal wrote:

A DC-blocking cap at the input?
Not likely.



It's between the high cut filter and the input to the amp stage, and
it's definatley a signal cap.

Looking throught the tone control section, I see another 33uf cap if
the tone controls are bypassed, a 220u if not. Also, a 10u after the
volume pot to the stage prior to the tone controls. So I guess there
are at least 3 caps in the signal stage.

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Sander deWaal Sander deWaal is offline
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Default On the origin and workings of "Fast" Power supplies

"Bob H." said:


A DC-blocking cap at the input?
Not likely.



It's between the high cut filter and the input to the amp stage, and
it's definatley a signal cap.



My comment was directed at Graham, he asked if the cap was somewhere
in the feedback loop.

That could only be possible, if the feedback resistor from the base of
the inverting input of the differential pair is connected to ground
with a cap.
IMO, that's not a harmful place ;-)


Looking throught the tone control section, I see another 33uf cap if
the tone controls are bypassed, a 220u if not. Also, a 10u after the
volume pot to the stage prior to the tone controls. So I guess there
are at least 3 caps in the signal stage.



The reason for the 100 uF being that large, is that in effect, all
caps are in series, with some resistors and pots inbetween.
This gives several different corner frequencies.


--
- Ever seen someone with 5.1 ears? So, what does that tell you? -
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Eeyore Eeyore is offline
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Default On the origin and workings of "Fast" Power supplies



Sander deWaal wrote:

"Bob H." said:

A DC-blocking cap at the input?
Not likely.


It's between the high cut filter and the input to the amp stage, and
it's definatley a signal cap.


My comment was directed at Graham, he asked if the cap was somewhere
in the feedback loop.

That could only be possible, if the feedback resistor from the base of
the inverting input of the differential pair is connected to ground
with a cap.
IMO, that's not a harmful place ;-)


It's potentially as equally harmful as the input cap actually.


Looking throught the tone control section, I see another 33uf cap if
the tone controls are bypassed, a 220u if not. Also, a 10u after the
volume pot to the stage prior to the tone controls. So I guess there
are at least 3 caps in the signal stage.


The reason for the 100 uF being that large, is that in effect, all
caps are in series, with some resistors and pots inbetween.
This gives several different corner frequencies.


If someone cares to offer me the working voltages at those point and the input
impedances I can easily work out if the use of zero-bias electrolytics is
'harmful' or not.

Graham



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Sander deWaal Sander deWaal is offline
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Default On the origin and workings of "Fast" Power supplies

Eeyore said:


That could only be possible, if the feedback resistor from the base of
the inverting input of the differential pair is connected to ground
with a cap.
IMO, that's not a harmful place ;-)



It's potentially as equally harmful as the input cap actually.



I disagree.
The signal amplitude at the inverting input is attenuated by the
feedback voltage divider, and there's a fairly constant DC offset
voltage across it.

The input cap has to deal with an unknown DC polarity at the input and
higher signal voltages, hence the need for a relatively large value
and a bipolar electrolytic.
I use Nichicon Muse ES caps for this application.


--
- Ever seen someone with 5.1 ears? So, what does that tell you? -
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Ruud Broens Ruud Broens is offline
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Default "Fast" Power supplies

4 Graham:

: : "Eeyore" wrote in message

http://www.bwspeakers.com/downloadFi...opment_ Paper
..pdf

"What is not so clear-cut is why different capacitors,
with ostensibly the same specification, can sound
so different from one another. The difficulty in mapping
physical properties to the perceived performance
characteristics further compounds the problem."

R.
extra bulletin


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Arny Krueger Arny Krueger is offline
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Default "Fast" Power supplies

"Ruud Broens" wrote in message

4 Graham:

"Eeyore" wrote
in message


http://www.bwspeakers.com/downloadFi...opment_ Paper
.pdf

"What is not so clear-cut is why different capacitors,
with ostensibly the same specification, can sound
so different from one another. The difficulty in mapping
physical properties to the perceived performance
characteristics further compounds the problem."


Just another example of the deep pit that people can put themselves in with
sighted, non-level-matched, non-time-synched listening evaluations.


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coffeedj coffeedj is offline
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Default "Fast" Power supplies

One of my concerns about massive C's in the power supply chain comes from
the fact that the HV supply to ground ends up participating in the signal
path. Hagerman uses 470nF bypasses on his 47uF PSU caps to overcome this
problem--and if one uses larger caps, then I would suspect a double by-pass
is needed to get the same result. I prefer the choke input filters--as less
C is needed to get equivalent ripple. The other issue of choke input
filters is that the output of the choke is a pure DC offest sin wave--and it
gets around the HF noise that comes from a C input PSU. Of course a larger
(and more expensive) choke is needed for choke input filters. Another plus:
if you are using a FW rectifier the choke input effectively knocks out
rectifer switching noise as well.

The question of "fast" is something I have also wondered about--and one of
these days I'll do a real world test of it. The point is that you want your
HT not to sag on high current peaks. And you don't want it to ring on
recovery from peaks. Theoretically, an infinitely large reservoir would fit
the bill--thus favoring the long C chain. But if your reservoir is not
approximately infinite then the large time constant is going to work against
recovery from long peak draw periods. Thus, a fast recovery system (small
C's) can work as well if properly designed to eliminate ringing. The other
element that helps a fast recovery system is obviously a power transformer
that is overspec--and thus doesn't contribute to the recovery time via
saturation (during peaks).

In practice I've noticed that commercially designed PSU on moderate priced
products tend to be running at close to the limits--thus saving cost. These
amps, in my experience, benefit from a beefer PSU of either variety.

YMMV--have fun and try a few different approaches.


"Iain Churches" wrote in message
...
There seem to be two schools of thought regarding linear PSUs
in valve tube/amps. Some favour a long chain with high capacitance
electrolytics. Others favour a simple C-L-C pi filter with caps of
47uF or so, saying that a "fast" psu sounds better.

With valve rectifiers, one is limited in the value of the first
electrolytic, but with FW bridges, these limitations no longer apply.

What type of supply do RATs prefer?
Does a "fast" supply sound different/better?
If so, how does this improvement manifest itself?

regards to all.
Iain







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John Byrns John Byrns is offline
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Default "Fast" Power supplies

In article ,
"coffeedj" wrote:

One of my concerns about massive C's in the power supply chain comes from
the fact that the HV supply to ground ends up participating in the signal
path. Hagerman uses 470nF bypasses on his 47uF PSU caps to overcome this
problem--and if one uses larger caps, then I would suspect a double by-pass
is needed to get the same result. I prefer the choke input filters--as less
C is needed to get equivalent ripple. The other issue of choke input
filters is that the output of the choke is a pure DC offest sin wave--and it
gets around the HF noise that comes from a C input PSU.


Are you sure it is really a "pure DC offest sin wave"? I was under the
impression that the output of a choke input PSU also included at least
the odd harmonics of the sine wave?

Of course a larger
(and more expensive) choke is needed for choke input filters. Another plus:
if you are using a FW rectifier the choke input effectively knocks out
rectifer switching noise as well.

The question of "fast" is something I have also wondered about--and one of
these days I'll do a real world test of it. The point is that you want your
HT not to sag on high current peaks. And you don't want it to ring on
recovery from peaks. Theoretically, an infinitely large reservoir would fit
the bill--thus favoring the long C chain. But if your reservoir is not
approximately infinite then the large time constant is going to work against
recovery from long peak draw periods. Thus, a fast recovery system (small
C's) can work as well if properly designed to eliminate ringing. The other
element that helps a fast recovery system is obviously a power transformer
that is overspec--and thus doesn't contribute to the recovery time via
saturation (during peaks).


"Peaks" on the load side of a power transformer don't cause saturation,
if anything they tend to reduce the possibility of transformer
saturation.

Regards,

John Byrns

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


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coffeedj coffeedj is offline
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Default "Fast" Power supplies

That is what one of the texts say--and it appeared to be true on the DSO.
I'll have to take a second look though to be sure.

"John Byrns" wrote in message
...
In article ,
"coffeedj" wrote:

One of my concerns about massive C's in the power supply chain comes from
the fact that the HV supply to ground ends up participating in the signal
path. Hagerman uses 470nF bypasses on his 47uF PSU caps to overcome this
problem--and if one uses larger caps, then I would suspect a double
by-pass
is needed to get the same result. I prefer the choke input filters--as
less
C is needed to get equivalent ripple. The other issue of choke input
filters is that the output of the choke is a pure DC offest sin wave--and
it
gets around the HF noise that comes from a C input PSU.


Are you sure it is really a "pure DC offest sin wave"? I was under the
impression that the output of a choke input PSU also included at least
the odd harmonics of the sine wave?

Of course a larger
(and more expensive) choke is needed for choke input filters. Another
plus:
if you are using a FW rectifier the choke input effectively knocks out
rectifer switching noise as well.

The question of "fast" is something I have also wondered about--and one
of
these days I'll do a real world test of it. The point is that you want
your
HT not to sag on high current peaks. And you don't want it to ring on
recovery from peaks. Theoretically, an infinitely large reservoir would
fit
the bill--thus favoring the long C chain. But if your reservoir is not
approximately infinite then the large time constant is going to work
against
recovery from long peak draw periods. Thus, a fast recovery system
(small
C's) can work as well if properly designed to eliminate ringing. The
other
element that helps a fast recovery system is obviously a power
transformer
that is overspec--and thus doesn't contribute to the recovery time via
saturation (during peaks).


"Peaks" on the load side of a power transformer don't cause saturation,
if anything they tend to reduce the possibility of transformer
saturation.

Regards,

John Byrns

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



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