[Multi-grid]

hey-Hey!!!,
If y'all were going to construct a power supply for a big tube amp( B+
~650, current ~350 mA) would you use Hg vapour tubes in the PS or
damper diodes? Seems both have some advantages. Glow is nice for
sure...
cheers,
Douglas

[jwvm]

On Oct 24, 11:10 pm, Multi-grid wrote:
hey-Hey!!!,
If y'all were going to construct a power supply for a big tube amp( B+
~650, current ~350 mA) would you use Hg vapour tubes in the PS or
damper diodes? Seems both have some advantages. Glow is nice for
sure...
cheers,
Douglas

Mercury vapor rectifiers have been obsolete for at least 30 years and
are a needless environmental hazard so its not clear why you would
want to use them The term "damper diode" can refer to either a tube or
a silicon diode and is intended for use in a television. Silicon
diodes represent a much better choice since they are considerably more
efficient. For a nice glow, try a fluorescent light but don't break
it.

[isw]

In article ,
Multi-grid wrote:

hey-Hey!!!,
If y'all were going to construct a power supply for a big tube amp( B+
~650, current ~350 mA) would you use Hg vapour tubes in the PS or
damper diodes? Seems both have some advantages. Glow is nice for
sure...

When I was designing transmitters for RCA Broadcast (late '60's), I did
the analysis that resulted in the replacement of mercury-vapor
rectifiers by a series string of silicon rectifiers in several of their
AM and FM transmitter models. Saved several hundred dollars per
transmitter while improving reliability and efficiency.

None of the engineers there thought that the tubes had the slightest
advantage, and were glad to get rid of them; what do you think the
advantages are?

Isaac

[Arny Krueger]

"Multi-grid" wrote in message
...
hey-Hey!!!,

If y'all were going to construct a power supply for a big tube amp( B+
~650, current ~350 mA) would you use Hg vapour tubes in the PS or
damper diodes?

Neither, I'd use silicon diodes.

[MC]

"Multi-grid" wrote in message
...
hey-Hey!!!,
If y'all were going to construct a power supply for a big tube amp( B+
~650, current ~350 mA) would you use Hg vapour tubes in the PS or
damper diodes? Seems both have some advantages. Glow is nice for
sure...
cheers,
Douglas

Why not silicon rectifiers? Assuming you're producing DC successfully,
tubes as rectifiers can't possibly make your amplifier sound any better...

[Multi-grid]

On Oct 26, 1:47 am, "MC" wrote:
"Multi-grid" wrote in message

...

hey-Hey!!!,
If y'all were going to construct a power supply for a big tube amp( B+
~650, current ~350 mA) would you use Hg vapour tubes in the PS or
damper diodes? Seems both have some advantages. Glow is nice for
sure...
cheers,
Douglas

Why not silicon rectifiers? Assuming you're producing DC successfully,
tubes as rectifiers can't possibly make your amplifier sound any better...

MC, on this I must respectfully disagree. I won't try to explain or
convert you. I think they do, and I will just leave it at that.
cheers,
Douglas

[Multi-grid]

On Oct 26, 1:32 am, jwvm wrote:
On Oct 24, 11:10 pm, Multi-grid wrote:

hey-Hey!!!,
If y'all were going to construct a power supply for a big tube amp( B+
~650, current ~350 mA) would you use Hg vapour tubes in the PS or
damper diodes? Seems both have some advantages. Glow is nice for
sure...
cheers,
Douglas

Mercury vapor rectifiers have been obsolete for at least 30 years and
are a needless environmental hazard so its not clear why you would
want to use them The term "damper diode" can refer to either a tube or
a silicon diode and is intended for use in a television. Silicon
diodes represent a much better choice since they are considerably more
efficient. For a nice glow, try a fluorescent light but don't break
it.

It would be a vacuum diode, 6AU4-ish, perhaps two or three in
parallel. I think I will not be using Si types, and while tryig not to
be disagreeable, Si wasn't one of the choices---though in retrospect,
I wasn't quite clear enough about that.

As to 866's, I like the blue glow. I have also liked the way amps I've
built with them work. There's not that much Hg, and I have lots ov
sulfur about just in case. Building amps is in part influenced by the
appearance, don't you think?
cheers,
Douglas

[MC]

"Multi-grid" wrote in message
...

Why not silicon rectifiers? Assuming you're producing DC successfully,
tubes as rectifiers can't possibly make your amplifier sound any
better...

MC, on this I must respectfully disagree. I won't try to explain or
convert you. I think they do, and I will just leave it at that.
cheers,
Douglas

And there are people who think the earth is flat. In the absence of
evidence or even plausible theory, I can only ignore your claim.

[[email protected]]

"As to 866's, I like the blue glow. I have also liked the way amps I've
built with them work. There's not that much Hg, and I have lots ov
sulfur about just in case. Building amps is in part influenced by the
appearance, don't you think?"

I have long wondered about uv risk to eye sight from them. It would be
worth some research.

Long ago I did tech work in a theater dept. at an university. They were
used in large banks for stage and house light dimmers. I always got a
strange feeling in that room and made a point not to look directly into
them and left as soon as possible.

[jwvm]

On Oct 26, 6:28 pm, wrote:
"As to 866's, I like the blue glow. I have also liked the way amps I've
built with them work. There's not that much Hg, and I have lots ov
sulfur about just in case. Building amps is in part influenced by the
appearance, don't you think?"

I have long wondered about uv risk to eye sight from them. It would be
worth some research.

Long ago I did tech work in a theater dept. at an university. They were
used in large banks for stage and house light dimmers. I always got a
strange feeling in that room and made a point not to look directly into
them and left as soon as possible.

Common glass does not pass UV very well so you probably would not have
too much about eye damage. Still, why someone wouldn't choose silicon
rectifiers for a mundane task like rectification is a bit of a mystery.

[MC]

"jwvm" wrote in message
...

Common glass does not pass UV very well so you probably would not have
too much about eye damage. Still, why someone wouldn't choose silicon
rectifiers for a mundane task like rectification is a bit of a mystery.

Right -- I can understand wanting to use retro technology for the effect,
for the antiquated appearance -- but not for performance, at least in this
case.

[Sonnova]

On Sat, 27 Oct 2007 20:03:56 -0700, MC wrote
(in article ):

"jwvm" wrote in message
...

Common glass does not pass UV very well so you probably would not have
too much about eye damage. Still, why someone wouldn't choose silicon
rectifiers for a mundane task like rectification is a bit of a mystery.

Right -- I can understand wanting to use retro technology for the effect,
for the antiquated appearance -- but not for performance, at least in this
case.

The tubed rectifiers effect a "soft turn-on" (I.E. the B+ comes up rather
slowly as the rectifiers start to conduct), which amplifier manufacturers
that use tube rectifiers say is less shock to the cold output tubes therefore
extending their life. Some use a relay and a timing circuit to delay the
application of B+ to the output tubes until they are warmed, but this is not
the same as bringing the B+ up slowly. Whether this is any more than hype, I
don't know, but I can't believe that the tube rectifiers take any more than a
couple of seconds to start conducting. Certainly not enough time for the
output tubes to heat up sufficiently to make any real difference. I once
reworked a pair of Dynaco 60-Watt monoblocs and replaced the tube rectifier
with an encapsulated bridge to replace the rectifier tube (a 5U4 is memory
serves). I noticed no change in the life of the output tubes.

[Norman M. Schwartz]

"MC" wrote in message ...
"jwvm" wrote in message
...

Common glass does not pass UV very well so you probably would not have
too much about eye damage. Still, why someone wouldn't choose silicon
rectifiers for a mundane task like rectification is a bit of a mystery.

Right -- I can understand wanting to use retro technology for the effect,
for the antiquated appearance -- but not for performance, at least in this
case.

_Certain wavelengths_ of UV light passed through my (any many other's)
windows to react with the glue in Maggi speakers resulting in severe damage.
Because of this about 20 years ago Magnepan began using a non-UV sensitive
adhesive.

[isw]

In article ,
Sonnova wrote:

On Sat, 27 Oct 2007 20:03:56 -0700, MC wrote
(in article ):

"jwvm" wrote in message
...

Common glass does not pass UV very well so you probably would not have
too much about eye damage. Still, why someone wouldn't choose silicon
rectifiers for a mundane task like rectification is a bit of a mystery.

Right -- I can understand wanting to use retro technology for the effect,
for the antiquated appearance -- but not for performance, at least in this
case.

The tubed rectifiers effect a "soft turn-on" (I.E. the B+ comes up rather
slowly as the rectifiers start to conduct), which amplifier manufacturers
that use tube rectifiers say is less shock to the cold output tubes therefore
extending their life. Some use a relay and a timing circuit to delay the
application of B+ to the output tubes until they are warmed, but this is not
the same as bringing the B+ up slowly. Whether this is any more than hype, I
don't know, but I can't believe that the tube rectifiers take any more than a
couple of seconds to start conducting. Certainly not enough time for the
output tubes to heat up sufficiently to make any real difference. I once
reworked a pair of Dynaco 60-Watt monoblocs and replaced the tube rectifier
with an encapsulated bridge to replace the rectifier tube (a 5U4 is memory
serves). I noticed no change in the life of the output tubes.

You have to be careful when replacing tube rectifiers with silicon
diodes -- moreso with vacuum units than with mercury vapor -- because
the conduction drop across the silicon devices is so much smaller than
that of tubes. The result can be an overvoltage condition on the filter
caps and possibly other components as well.

ISTR that mercury-vapor recifiers can oscillate under certain conditions
-- become transmitters, that is -- unless proper precautions are taken.

Isaac

[Sonnova]

On Mon, 29 Oct 2007 15:45:35 -0700, isw wrote
(in article ):

In article ,
Sonnova wrote:

On Sat, 27 Oct 2007 20:03:56 -0700, MC wrote
(in article ):

"jwvm" wrote in message
...

Common glass does not pass UV very well so you probably would not have
too much about eye damage. Still, why someone wouldn't choose silicon
rectifiers for a mundane task like rectification is a bit of a mystery.

Right -- I can understand wanting to use retro technology for the effect,
for the antiquated appearance -- but not for performance, at least in this
case.

The tubed rectifiers effect a "soft turn-on" (I.E. the B+ comes up rather
slowly as the rectifiers start to conduct), which amplifier manufacturers
that use tube rectifiers say is less shock to the cold output tubes
therefore
extending their life. Some use a relay and a timing circuit to delay the
application of B+ to the output tubes until they are warmed, but this is
not
the same as bringing the B+ up slowly. Whether this is any more than hype,
I
don't know, but I can't believe that the tube rectifiers take any more than
a
couple of seconds to start conducting. Certainly not enough time for the
output tubes to heat up sufficiently to make any real difference. I once
reworked a pair of Dynaco 60-Watt monoblocs and replaced the tube rectifier
with an encapsulated bridge to replace the rectifier tube (a 5U4 is memory
serves). I noticed no change in the life of the output tubes.

You have to be careful when replacing tube rectifiers with silicon
diodes -- moreso with vacuum units than with mercury vapor -- because
the conduction drop across the silicon devices is so much smaller than
that of tubes. The result can be an overvoltage condition on the filter
caps and possibly other components as well.

Well, yes. One cannot just swap-out the tube(s) for silicon diodes. One has
to re-design the power supply as well. Many tube rectifiers, are, for
instance, single ended and most silicon replacements are bridges (though
obviously not always). They require capacitors with higher voltage ratings
and most hobbyists use much larger capacitors as well.

ISTR that mercury-vapor recifiers can oscillate under certain conditions
-- become transmitters, that is -- unless proper precautions are taken.

That could be. I can see them acting like a so-called relaxation oscillator
under certain circumstances, substituting the mercury-vapor tubes for the
neon lamps used in purpose-built relaxation oscillators, I suppose.

Isaac

[MC]

"Sonnova" wrote in message
...
On Sat, 27 Oct 2007 20:03:56 -0700, MC wrote
(in article ):

Right -- I can understand wanting to use retro technology for the effect,
for the antiquated appearance -- but not for performance, at least in
this
case.

The tubed rectifiers effect a "soft turn-on" (I.E. the B+ comes up rather
slowly as the rectifiers start to conduct), which amplifier manufacturers
that use tube rectifiers say is less shock to the cold output tubes
therefore
extending their life.

Ah... Perhaps more importantly, it is less shock to the filter capacitors.
I should have remembered this, since it is a consideration when changing
tube rectifiers to silicon in older equipment of any sort (I'm thinking
mainly old test equipment, of which I have a lot).

Still, for a new design I'd address the problem some other way. New,
correctly chosen filter capacitors shouldn't need this kind of protection.
And I'm not sure whether there is really stress on an output tube when you
apply B+ before the cathode warms up. What form would the stress take?
Conduction is limited by the incompletely-heated cathode.

[Sonnova]

On Sun, 4 Nov 2007 07:40:48 -0800, MC wrote
(in article ):

"Sonnova" wrote in message
...
On Sat, 27 Oct 2007 20:03:56 -0700, MC wrote
(in article ):

Right -- I can understand wanting to use retro technology for the effect,
for the antiquated appearance -- but not for performance, at least in
this
case.

The tubed rectifiers effect a "soft turn-on" (I.E. the B+ comes up rather
slowly as the rectifiers start to conduct), which amplifier manufacturers
that use tube rectifiers say is less shock to the cold output tubes
therefore
extending their life.

Ah... Perhaps more importantly, it is less shock to the filter capacitors.
I should have remembered this, since it is a consideration when changing
tube rectifiers to silicon in older equipment of any sort (I'm thinking
mainly old test equipment, of which I have a lot).

I should have remembered it also. You are absolutely correct.

Still, for a new design I'd address the problem some other way. New,
correctly chosen filter capacitors shouldn't need this kind of protection.
And I'm not sure whether there is really stress on an output tube when you
apply B+ before the cathode warms up. What form would the stress take?
Conduction is limited by the incompletely-heated cathode.

I'm not sure. This could be one of those apocryphal myths. Now that I think
about it, I don't see what bringing the B+ up slowly after the heater is up
to temperature could possibly do for a tube that would tend to extend it's
life.

[[email protected]]

On Nov 4, 8:07 pm, Sonnova wrote:
I'm not sure. This could be one of those apocryphal myths. Now that I think
about it, I don't see what bringing the B+ up slowly after the heater is up
to temperature could possibly do for a tube that would tend to extend it's
life.

Cathode stripping is usually cited as the issue - applying B+ before
the cathode is up to temp means oxide material may be pulled from the
cathode because there is no electron space charge built up. The 5AR4
(GZ34) indirectly heated rectifier was used in many vintage designs to
provide a delayed B+ ramp-up to the rest of the tubes (I guess a 5AR4
was cheaper than a pair of KT-66s even back in the good ole days).

I'd suggest using 3B28 xenon gas rectifiers instead of 866 mercury
vapor rectifiers.
a) You definitely need to let 866s warm up for a minute before
applying HV or they'll flash over and potentially trash your power
xfmr (ref. good article on care and feeding of MV rectifiers in the
old RCA Transmitting Tubes handbook). 3B28 has shorter warm-up period.
b) MV rectifiers are notorious for producing RF hash which may/may not
get into your tuner or preamp.
c) 3B28 xenon glow has no UV and is still aesthetically pleasing.
cheers,
Nick

[Randy Yates]

writes:

c) 3B28 xenon glow has no UV and is still aesthetically pleasing.

Does anyone know if the purple-glowing tube in the old Leslie
speaker model 122/145 tube amps was this 866? It sure did look
neat!
--
% Randy Yates % "She tells me that she likes me very much,
%% Fuquay-Varina, NC % but when I try to touch, she makes it
%%% 919-577-9882 % all too clear."
%%%% % 'Yours Truly, 2095', *Time*, ELO
http://www.digitalsignallabs.com

[isw]

In article ,
Randy Yates wrote:

writes:

c) 3B28 xenon glow has no UV and is still aesthetically pleasing.

Does anyone know if the purple-glowing tube in the old Leslie
speaker model 122/145 tube amps was this 866? It sure did look
neat!

Probably not. Most likely it was a voltage regulator.

Isaac

[BEAR]

MC wrote:
"Multi-grid" wrote in message
...

Why not silicon rectifiers? Assuming you're producing DC successfully,
tubes as rectifiers can't possibly make your amplifier sound any
better...
MC, on this I must respectfully disagree. I won't try to explain or
convert you. I think they do, and I will just leave it at that.
cheers,
Douglas

And there are people who think the earth is flat. In the absence of
evidence or even plausible theory, I can only ignore your claim.

To isw and MC, others etc...

There are measureable differences between rectifiers.

That includes silicon, selenium, tube, etc.

There are two primary "advantages" to tube type rectifiers in common
audio use (everything else I say here refers to common audio application):

- soft recovery
- slow turn on

There are some disadvantages to tube type rectifiers:
- "mercury" types make noise and take excess time to warm up
- they have "extra" voltage drop, and therefore are higher impedance
- they wear out and fail - this may cause physical damage to an amp given
the right conditions

Tube type rectifiers *can sound "better"*, that is mostly due to the
soft recovery aspect.

The cathode stripping possibility is greatest with *directly heated* tubes
like a 300B or 2A3, for example. Less so with indirectly heated tubes, but
still not very good for them. Delay ur B+ turn on if using solid state
rectification with tubes for best results.

Nowadays there are "soft recovery" silicon devices, such as the HEXFRED
and others. They often result in "better" perceived sound when substituted
for standard silicon rectifiers.

The presumed causal factor is the noise created by fast recovery rectifiers
as the result of the sharp recovery function.
You can measure it and see it. Many seem to be able to hear a change when
soft recovery diodes (tube or silicon) are used as substitues for standard
rectification. You may or may not be able to hear that sort of thing.

No power supply *ever* has made "perfect DC." There is always some sort of
noise and artifact. Even batteries have been shown to be noiser than some
solid state regulation schemes!

How much of that is audible I leave to others to determine for themselves.
For most casual listening and construction it may not matter.
Don't want to engage in that debate.
However there is a clear consensus that some sort of audible change often does
occur when the rectification element is changed.

_-_-bear

[MC]

Ah. I was assuming there would be adequate regulation and noise filtering
after the rectifier. If not, then the rectifier does make a difference.
But wouldn't a silicon diode with a capacitor across it have "soft recovery"
too?

[jwvm]

On Dec 25, 11:48 am, "MC" wrote:
Ah. I was assuming there would be adequate regulation and noise filtering
after the rectifier. If not, then the rectifier does make a difference.
But wouldn't a silicon diode with a capacitor across it have "soft recovery"
too?

Good power supply design isn't rocket science. With effective use of
filtering and bypass capacitors, it is not obvious why noise should be
much of a problem. Even low-cost amplifiers with headphones can have
no audible sound at low volume settings. At higher volume settings,
white noise will be present but this is not due to power supply
failings.

One might note that power supply noise at the output stage should not
be much of a problem anyway, at least for common collector/drain type
circuits. The high impedance (Early effect) of output devices
effectively isolates the power supply from the loudspeaker unless they
saturate.

[isw]

In article ,
jwvm wrote:

On Dec 25, 11:48 am, "MC" wrote:
Ah. I was assuming there would be adequate regulation and noise filtering
after the rectifier. If not, then the rectifier does make a difference.
But wouldn't a silicon diode with a capacitor across it have "soft recovery"
too?

Good power supply design isn't rocket science. With effective use of
filtering and bypass capacitors, it is not obvious why noise should be
much of a problem. Even low-cost amplifiers with headphones can have
no audible sound at low volume settings. At higher volume settings,
white noise will be present but this is not due to power supply
failings.

One might note that power supply noise at the output stage should not
be much of a problem anyway, at least for common collector/drain type
circuits. The high impedance (Early effect) of output devices
effectively isolates the power supply from the loudspeaker unless they
saturate.

I suppose it's possible that "soft" rectification makes a
less-than-competent grounding setup more-or-less adequte. High-current
pulses from "fast' rectifiers could cause voltage drops in unintended
places, producing hum or buzz.

Isaac

[Paul[_11_]]

On 27 Dec 2007 16:46:17 GMT, isw wrote:
.....stuff deleted.....

I suppose it's possible that "soft" rectification makes a
less-than-competent grounding setup more-or-less adequte. High-current
pulses from "fast' rectifiers could cause voltage drops in unintended
places, producing hum or buzz.


If you are rectifying 50/60 Hz power, it is silly to specify soft
or fast rectifiers. Due to the low dv/dt (change of voltage with
respect to time), there is little charge "caught " in the rectifier
junction that will cause current spikes on the reverse voltage. If you
have a switching power supply on the other hand, with high rates of
change of voltage, yes, you will have current spikes at the reverse
voltage beginning, as the charge is pulled out of the junction.
I tried this about 10 years ago, with spectrum analyzer, and a
special circuit that is commercially used to test EMI that propagates
from a power supply. It made diddly difference what type of diode was
used. All the harmonic content coulkd be explained purely from the
normal rectified sinusoid. That is for a sinewave supply.
What DID make a difference was leakage inductances and stray
interwinding capacitances. Those were controlled by RF bypass caps to
the chassis, series bifilar inductors, and most importantly, a 0.1 mf
capacitor in series with a 22 ohm resistor, and this combo placed
directly across the power transformer primary. That circuit would
lower the Q and dampen most of the resonances. The type of capacitor
and resistor are extremely critical for safety reasons. All components
on the line side MUST be rated by the appropriate standards
committees. Otherwise you are taking chances of burning your house
down.
I did work for a large (un-named) corporation where in the past
they didn't specify the correct components..... several families lost
their lives to the wrong choice of line capacitors.
Don't f... around with power line components.
As another weird thing, diodes can affect jitter on a CD player as
the RF currents (from the crystal timebase) have their paths out of
the amp turned on and off 60/120 times a second. Tha cure for that is
not diode type, but proper elimination of RF leakage from the
oscillators.

[BEAR]

jwvm wrote:
On Dec 25, 11:48 am, "MC" wrote:
Ah. I was assuming there would be adequate regulation and noise filtering
after the rectifier. If not, then the rectifier does make a difference.
But wouldn't a silicon diode with a capacitor across it have "soft recovery"
too?

No.
Snubbers can help, but they are not the same thing.

----------------

Good power supply design isn't rocket science.

Nice assertion.
However, power supply design is not all that simple.
Once you get past the basic idea of rectification and simple regulation that is.
Some people look at impedance vs. frequency and the spectra of noise, and
other things...

With effective use of
filtering and bypass capacitors, it is not obvious why noise should be
much of a problem. Even low-cost amplifiers with headphones can have
no audible sound at low volume settings. At higher volume settings,
white noise will be present but this is not due to power supply
failings.

No, it is not immediately obvious.


One might note that power supply noise at the output stage should not
be much of a problem anyway, at least for common collector/drain type
circuits. The high impedance (Early effect) of output devices
effectively isolates the power supply from the loudspeaker unless they
saturate.

Oddly enough some people view this situation rather differently.
It may be useful to view the load as directly connected to the power supply.
Take a look at the Acoustat TNT 200 amplifier's schematic if you doubt this
may be possible.

You'd best not have a high impedance at the output side of your power amp,
so I'm not sure what ur thinking about... most outpoots today are followers.

_-_-bear

[BEAR]

Paul wrote:
On 27 Dec 2007 16:46:17 GMT, isw wrote:
....stuff deleted.....
I suppose it's possible that "soft" rectification makes a
less-than-competent grounding setup more-or-less adequte. High-current
pulses from "fast' rectifiers could cause voltage drops in unintended
places, producing hum or buzz.


If you are rectifying 50/60 Hz power, it is silly to specify soft
or fast rectifiers. Due to the low dv/dt (change of voltage with
respect to time), there is little charge "caught " in the rectifier
junction that will cause current spikes on the reverse voltage. If you
have a switching power supply on the other hand, with high rates of
change of voltage, yes, you will have current spikes at the reverse
voltage beginning, as the charge is pulled out of the junction.
I tried this about 10 years ago, with spectrum analyzer, and a
special circuit that is commercially used to test EMI that propagates
from a power supply. It made diddly difference what type of diode was
used. All the harmonic content coulkd be explained purely from the
normal rectified sinusoid. That is for a sinewave supply.

Wonder how much current was involved in that supply?
Suspect not all that much...

There have been numerous papers on this subject that show the
very thing you claim to have not found, so perhaps that was the
differential??

What DID make a difference was leakage inductances and stray
interwinding capacitances. Those were controlled by RF bypass caps to
the chassis, series bifilar inductors, and most importantly, a 0.1 mf
capacitor in series with a 22 ohm resistor, and this combo placed
directly across the power transformer primary. That circuit would
lower the Q and dampen most of the resonances. The type of capacitor
and resistor are extremely critical for safety reasons. All components
on the line side MUST be rated by the appropriate standards
committees. Otherwise you are taking chances of burning your house
down.

When you say resonances here, what are your referring to on a supply
that you say is sinusoidal supplied *and* has a slow dv/dt??

And are the bifilar inductor/bypass cap combos on the primary or secondary
side?? (or both?)

I did work for a large (un-named) corporation where in the past
they didn't specify the correct components..... several families lost
their lives to the wrong choice of line capacitors.

No fuses?
Hot chassis?
Fires?
No three wire safety power cords?
I'm confused!

Don't f... around with power line components.
As another weird thing, diodes can affect jitter on a CD player as
the RF currents (from the crystal timebase) have their paths out of
the amp turned on and off 60/120 times a second. Tha cure for that is
not diode type, but proper elimination of RF leakage from the
oscillators.

Ummm... unclear here too... "their paths out of the amp"?? What amp?
How is the output of the xtal oscillator modulated by the rectified line?
And how does the elimination of RF leakage from the oscillator(s) going
to effect what? Sorry, I'm interested in this, but confused by the
explanation.

_-_-bear

[Paul[_11_]]

On 1 Jan 2008 16:16:27 GMT, bear wrote:

Paul wrote:
On 27 Dec 2007 16:46:17 GMT, isw wrote:
....stuff deleted.....
I suppose it's possible that "soft" rectification makes a
less-than-competent grounding setup more-or-less adequte. High-current
pulses from "fast' rectifiers could cause voltage drops in unintended
places, producing hum or buzz.


If you are rectifying 50/60 Hz power, it is silly to specify soft
or fast rectifiers. Due to the low dv/dt (change of voltage with
respect to time), there is little charge "caught " in the rectifier
junction that will cause current spikes on the reverse voltage. If you
have a switching power supply on the other hand, with high rates of
change of voltage, yes, you will have current spikes at the reverse
voltage beginning, as the charge is pulled out of the junction.
I tried this about 10 years ago, with spectrum analyzer, and a
special circuit that is commercially used to test EMI that propagates
from a power supply. It made diddly difference what type of diode was
used. All the harmonic content coulkd be explained purely from the
normal rectified sinusoid. That is for a sinewave supply.

Wonder how much current was involved in that supply?
Suspect not all that much...

About 1 ampere (primary side). I tried different currents, no real
difference to harmonic spectrum.


There have been numerous papers on this subject that show the
very thing you claim to have not found, so perhaps that was the
differential??

Yup... I know the paper you're thinking of. That was one that
appeared in one of the audio rags, it turned out that that experiment
was only repeatable (showing high harmonic content) if the spectrum
analyzer was scanned too fast. I was able to duplicate (more or less)
their incorrect results. The paper was done by someone who didn't
understand the equipment. The paper was obviously not peer
reviewed.Many of the auiophile papers are of dubious quality, even a
few from some very respected scientists.

What DID make a difference was leakage inductances and stray
interwinding capacitances. Those were controlled by RF bypass caps to
the chassis, series bifilar inductors, and most importantly, a 0.1 mf
capacitor in series with a 22 ohm resistor, and this combo placed
directly across the power transformer primary. That circuit would
lower the Q and dampen most of the resonances. The type of capacitor
and resistor are extremely critical for safety reasons. All components
on the line side MUST be rated by the appropriate standards
committees. Otherwise you are taking chances of burning your house
down.

When you say resonances here, what are your referring to on a supply
that you say is sinusoidal supplied *and* has a slow dv/dt??


Any 50/60 Hz power supply has very slow dv/dt compared to a switching
power supply. There is no need for fast/soft recovery diodes for a
normal wall socket power., UNLESS it runs a switching power supply off
the rough DC, as most PC power supplies do.

And are the bifilar inductor/bypass cap combos on the primary or secondary
side?? (or both?)

For max. isolation, they were on the primary side. Filters must be
designed for max. attenuation - that means you need to consider the
various impedances to ground and to source(s). Filters designed for
typical line filters may need extra components at high frequencies,
since stray capacitance can give low impedances and reduced
attenuation at greater than 50 MHz. The resonances due to transformer
leakage inductances and interwinding capacitances were below several
MHz. For the purposes of determining the effect of different diodes I
ran the measurements with and without filters. There were some
harmonics that were higher due to resonances, but by optimizing the
filter (damped), they dropped to reasonable values.
filtering for analog circuits is quite different that that required
for digital or computer sources. Properly working audio analog
equipment doesn't usually generate very much junk that can be injected
into the line, unlike digital. The filtering is usually
unidirectional, that is to cut down on the stuff coming into the
device from the line. In the case of large common-mode signals on the
power lines , you might need extra components on the line to limit
noise currents. That can get tricky, since you can't raise the
impedance of the ground connection for safety reasons. Isolation
transformers can work, but they have interwinding capacitances that
end up giving you back the same problem.
Linn designed little switching supplies (their "Brilliant" supplies)
that replaced their toroidal power transformers, and got around this
problem by using transormers with low parasitics.
....ooops... I digress....

I did work for a large (un-named) corporation where in the past
they didn't specify the correct components..... several families lost
their lives to the wrong choice of line capacitors.

No fuses?
Hot chassis?
Fires?
No three wire safety power cords?
I'm confused!

Correct components I am talking about are the bypass caps, damping
resistors, and of course all the other stuff you mention like fuses,
etc. The wrong choice of caps was responsible for the fires. They
promptly changed types, and installed components that would not
readily burn. When you choose capacitors or any other component that
is placed on the line side, it must meet proper safety specs, and I'm
not talking about silly audiophile rated components.

Don't f... around with power line components.
As another weird thing, diodes can affect jitter on a CD player as
the RF currents (from the crystal timebase) have their paths out of
the amp turned on and off 60/120 times a second. Tha cure for that is
not diode type, but proper elimination of RF leakage from the
oscillators.

Ummm... unclear here too... "their paths out of the amp"?? What amp?
How is the output of the xtal oscillator modulated by the rectified line?
And how does the elimination of RF leakage from the oscillator(s) going
to effect what? Sorry, I'm interested in this, but confused by the
explanation.

I did a lot of messing around with jitter (CD player)and found that in
several instances that in the case of a poorly designed oscillator,
the RF leakage can cause jitter because of RF finding a path out from
the power supply. The component of audio that was caused by this
jitter was in the order of -90 to -95 db from full output. In this
case the diodes were the path out. By installing ferrite tubes on the
supply lines I was able to control it, but proper shielding and
termination of the clock lines was more effective.
-Paul