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Iain Churches Iain Churches is offline
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Default Shielded mains cable

I have just be evaluating a German built tube amp
(4 pairs of EL34 in push pull parallel) It was supplied
with a mains cable, which in addition to the L, N and
Earth wires, had an external woven copper plaid
screen/shield, under the clear plastic outer cover.

This shield appears to be connected to ground at
the amp end only.

I have seen something similar in studio/broadcast
control room racks, where test equipment was built
in, and powered from an AC outlet within the same rack.
The mains leads had a screen to prevent the possibility
of AF signals affecting measurements.

But what about in the case of audio equipment
built for use in the domestic environment?
Any opinions?

Regards to all
Iain



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Chris Hornbeck Chris Hornbeck is offline
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Default Shielded mains cable

On Tue, 29 May 2007 08:31:07 +0300, "Iain Churches"
wrote:

I have just be evaluating a German built tube amp
(4 pairs of EL34 in push pull parallel) It was supplied
with a mains cable, which in addition to the L, N and
Earth wires, had an external woven copper plaid
screen/shield, under the clear plastic outer cover.

This shield appears to be connected to ground at
the amp end only.

I have seen something similar in studio/broadcast
control room racks, where test equipment was built
in, and powered from an AC outlet within the same rack.
The mains leads had a screen to prevent the possibility
of AF signals affecting measurements.

But what about in the case of audio equipment
built for use in the domestic environment?
Any opinions?


Most all music-oriented audio guys will tend to forget
completely about all of the other "invisible" AC wiring
contributing to their little slice of heaven. Here
in big-time audio land, I have completely shielded
oxygen-free wiring from all sockets back to the breakers
and all of the way back from my house to Nuclear One in
Russellville, the only really pure source of power in the area.

Anybody who does less is just kidding himself.

Much thanks, as always,

Chris Hornbeck
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Default Shielded mains cable


"Chris Hornbeck" wrote in message
...
On Tue, 29 May 2007 08:31:07 +0300, "Iain Churches"
wrote:

I have just be evaluating a German built tube amp
(4 pairs of EL34 in push pull parallel) It was supplied
with a mains cable, which in addition to the L, N and
Earth wires, had an external woven copper plaid
screen/shield, under the clear plastic outer cover.

This shield appears to be connected to ground at
the amp end only.

I have seen something similar in studio/broadcast
control room racks, where test equipment was built
in, and powered from an AC outlet within the same rack.
The mains leads had a screen to prevent the possibility
of AF signals affecting measurements.

But what about in the case of audio equipment
built for use in the domestic environment?
Any opinions?


Most all music-oriented audio guys will tend to forget
completely about all of the other "invisible" AC wiring
contributing to their little slice of heaven. Here
in big-time audio land, I have completely shielded
oxygen-free wiring from all sockets back to the breakers
and all of the way back from my house to Nuclear One in
Russellville, the only really pure source of power in the area.

Anybody who does less is just kidding himself.


Thanks Chris. I value your opinion:-) I am glad to see
that you are keeping up the traditions of the true audiophile:-)

But seriously, this cable is included with the amp as a replacement
for the standard IEC kettle cable which we use in Europe. There
was no big fuss or hype. I was interested to know what the thinking
behind it might be.

Perhaps they just wanted to supply a product with high perceived-
quality down to the last nut and bolt.

Cordially,
Iain



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Patrick Turner Patrick Turner is offline
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Default Shielded mains cable



Iain Churches wrote:

"Chris Hornbeck" wrote in message
...
On Tue, 29 May 2007 08:31:07 +0300, "Iain Churches"
wrote:

I have just be evaluating a German built tube amp
(4 pairs of EL34 in push pull parallel) It was supplied
with a mains cable, which in addition to the L, N and
Earth wires, had an external woven copper plaid
screen/shield, under the clear plastic outer cover.

This shield appears to be connected to ground at
the amp end only.

I have seen something similar in studio/broadcast
control room racks, where test equipment was built
in, and powered from an AC outlet within the same rack.
The mains leads had a screen to prevent the possibility
of AF signals affecting measurements.

But what about in the case of audio equipment
built for use in the domestic environment?
Any opinions?


Most all music-oriented audio guys will tend to forget
completely about all of the other "invisible" AC wiring
contributing to their little slice of heaven. Here
in big-time audio land, I have completely shielded
oxygen-free wiring from all sockets back to the breakers
and all of the way back from my house to Nuclear One in
Russellville, the only really pure source of power in the area.

Anybody who does less is just kidding himself.


Thanks Chris. I value your opinion:-) I am glad to see
that you are keeping up the traditions of the true audiophile:-)

But seriously, this cable is included with the amp as a replacement
for the standard IEC kettle cable which we use in Europe. There
was no big fuss or hype. I was interested to know what the thinking
behind it might be.

Perhaps they just wanted to supply a product with high perceived-
quality down to the last nut and bolt.

Cordially,
Iain


Never mind Chris, the bakeground newkelear radiation does thangs to
audiopharles' marnds.

But a shield on mains cables connected to the chassis reduces possible
pick up of switching noise by other audio cabling nearby.

If a fault happens, the chassis is reliably connected to earth via the
green/yellow wire to the
earth buss, and if there is large current from a mains winding becoming
grounded,
it don't run down the shield, but down the earth wire only.

Behind many equipment stands owned by audiphiles there is often a mass
of tangled cables running
all over the place. Screening reduces noise.

Patrick Turner.
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Default Shielded mains cable



Chris Hornbeck wrote:

Here in big-time audio land, I have completely shielded
oxygen-free wiring from all sockets back to the breakers
and all of the way back from my house to Nuclear One in
Russellville, the only really pure source of power in the area.

Anybody who does less is just kidding himself.


LOL !

Thanks for that gem of wisdom Chris.

Graham



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Patrick Turner wrote:

But a shield on mains cables connected to the chassis reduces possible
pick up of switching noise by other audio cabling nearby.


Not true.

Graham

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"François Yves Le Gal" wrote:

"Iain Churches" wrote:

But what about in the case of audio equipment
built for use in the domestic environment?


Shielded mains cables can slightly reduce lead-induced hum and noise,


It certainly won't affect noise. Do please tell me more about this
'lead-induced' noise.

And how again does it reduce hum ?


a boon in consumer installations where many unbalanced signal leads are very
close to each other.


What difference would the proximity of lots of screened unbalanced signals make
?

Graham


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"François Yves Le Gal" wrote:

Eeyore wrote:

It certainly won't affect noise.


Of course it does. Just do a couple of measurements.


Talk is cheap. Have *YOU* any data to support this allegation ?


Do please tell me more about this
'lead-induced' noise.


RFI et al. cfr. Electronics 101.


More cheap talk. Any supporting data ?

If there's any RFI about, putting a screen on the mains lead won't affect how signal
cables are affected.

Besides, good (well designed) audio equipment these days should not be affected by
RFI.


And how again does it reduce hum ?


You've missed Electronics 102, haven't you?


You did apparentyl; since you can't put it down on paper.


What difference would the proximity of lots of screened unbalanced signals make

?

You've also failed Electronics 103, haven't you?


I'm sick of idiot fantasists like you and their magic cables. You forgot to mention
how important the snake oil is too.

Graham

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Default Shielded mains cable



But what about in the case of audio equipment
built for use in the domestic environment?
Any opinions?


It would help to reduce stray electrostatic 60Hz hum fields from
invading audio patch cords. Belden makes shielded IEC computer power
cords with shielding, Sun Microsystems used them on their workstations.

As for the house wire in the walls, "BX" armored cable would be a good
choice. The current carrying conductors inside that armor are
essentially a twisted pair, about one twist per 10cm. And around that
is the armor shield, which also has a bare conductor just under it to
maintain a low resistance continuity. It looks a lot like regular
twisted pair shielded audio signal cable used in radio stations and
such, but on steroids. So tell the electrician you want him to use BX
cable in your audio palace.
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But what about in the case of audio equipment
built for use in the domestic environment?


Shielded mains cables can slightly reduce lead-induced hum and noise,



It certainly won't affect noise. Do please tell me more about this
'lead-induced' noise.


Must be the lead in the solder.... :-)


And how again does it reduce hum ?


The shield on the power cord would reduce the *electrostatic* leakage
from the cord. It won't reduce *electromagnetic* leakage, but the fact
that the currents on both current carrying conductors in the cord should
cancel, to cancel that out.



a boon in consumer installations where many unbalanced signal leads are very
close to each other.



What difference would the proximity of lots of screened unbalanced signals make


Every dB of reduction of hum you can get from the shielded power cable,
and from the patch cords ("interconnects") helps. If you have a system
that would normally have 120dB S/N. Now, if you want to listen to AM
radio or some scratchy vinyl (because you like the programming, and it's
not available on a lower noise source), then the shielded power cord
probably won't be noticed.

Shielded power cords have a valid reason to exist, unlike those wooden
knobs for the volume control of your amp, that supposedly makes for
smoother sound. Or the speaker cable supports to prop them off the floor.


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robert casey wrote:

But what about in the case of audio equipment
built for use in the domestic environment?
Any opinions?


It would help to reduce stray electrostatic 60Hz hum fields from
invading audio patch cords.


Would it now ?

Belden makes shielded IEC computer power
cords with shielding, Sun Microsystems used them on their workstations.


Not for this reason.


As for the house wire in the walls, "BX" armored cable would be a good
choice. The current carrying conductors inside that armor are
essentially a twisted pair, about one twist per 10cm. And around that
is the armor shield, which also has a bare conductor just under it to
maintain a low resistance continuity. It looks a lot like regular
twisted pair shielded audio signal cable used in radio stations and
such, but on steroids. So tell the electrician you want him to use BX
cable in your audio palace.


The main problem from ac line current is the associated magnetic field. A
shielded power cable will do precisely squat about this.

Electrostatic coupling is so fabulously tiny as to be not worth considering.

Graham


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robert casey wrote:

As for the house wire in the walls, "BX" armored cable would be a good
choice. The current carrying conductors inside that armor are
essentially a twisted pair, about one twist per 10cm. And around that
is the armor shield, which also has a bare conductor just under it to
maintain a low resistance continuity. It looks a lot like regular
twisted pair shielded audio signal cable used in radio stations and
such, but on steroids. So tell the electrician you want him to use BX
cable in your audio palace.


The twisting will do the good, not the shielding. Save money and forget the
shielding.

Graham


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The twisting will do the good, not the shielding. Save money and forget the
shielding.



Okay, but realize that "Romex" cable is not usually twisted pair. It's
usually a flat ribbon.
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robert casey wrote:

Eeyore wrote:

And how again does it reduce hum ?


The shield on the power cord would reduce the *electrostatic* leakage
from the cord.


Into the shield of the interconnect. Not into the signal conductor. A few microamps
(if as much as that) in the shield are going to do sweet bugger all.


It won't reduce *electromagnetic* leakage, but the fact
that the currents on both current carrying conductors in the cord should
cancel, to cancel that out.


Only if there's tightly twisted which most certainly they aren't.


What difference would the proximity of lots of screened unbalanced signals make


Every dB of reduction of hum you can get from the shielded power cable,
and from the patch cords ("interconnects") helps. If you have a system
that would normally have 120dB S/N.


I don't think you're going to find any system that can do that.


Now, if you want to listen to AM
radio or some scratchy vinyl (because you like the programming, and it's
not available on a lower noise source), then the shielded power cord
probably won't be noticed.


The point you're making is one of masking effect which is valid. However I've yet to
hear any interconnect hum simply by bring a live but non-current carrying mains lead
near it.


Shielded power cords have a valid reason to exist, unlike those wooden
knobs for the volume control of your amp, that supposedly makes for
smoother sound. Or the speaker cable supports to prop them off the floor.


The only valid reason I can think of is for IT equipment to meet regulatory
requirements, not for any perceived or real benefit to hi-fi.

Graham


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robert casey wrote:

The twisting will do the good, not the shielding. Save money and forget the
shielding.


Okay, but realize that "Romex" cable is not usually twisted pair. It's
usually a flat ribbon.


I've no idea if it would meet your 'code' but twisted individual conductors for
the live and neutral would work very well.

Graham




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The twisting will do the good, not the shielding. Save money and forget the
shielding.


In which case, just twisting the 2 wire zip cord power cords on all your
audio boxes (amps, CD players, etc) would be enough. Something like one
twist per 3cm should do. The cords will tend to untwist themselves at
first, but a few weeks the cord twists will "set" into the cord
insulation. This costs exactly nothing, and you don't have to break out
the soldering iron or pop the lid off anything...
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Default Shielded mains cable

In article k.net,
robert casey wrote:


But what about in the case of audio equipment
built for use in the domestic environment?
Any opinions?


It would help to reduce stray electrostatic 60Hz hum fields from
invading audio patch cords. Belden makes shielded IEC computer power
cords with shielding, Sun Microsystems used them on their workstations.


I hated those, they were way too stiff, and for some reason we had
barrels and barrels of extras, I can't remember how that came about,
they must have shipped 4 or 5 with every work station.

As for the house wire in the walls, "BX" armored cable would be a good
choice. The current carrying conductors inside that armor are
essentially a twisted pair, about one twist per 10cm. And around that
is the armor shield, which also has a bare conductor just under it to
maintain a low resistance continuity. It looks a lot like regular
twisted pair shielded audio signal cable used in radio stations and
such, but on steroids. So tell the electrician you want him to use BX
cable in your audio palace.


Couldn't that land him in hot water when the electrical inspector finds
out that he used BX cable instead of following the electrical code?


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/
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Default Shielded mains cable

In article .net,
robert casey wrote:

What difference would the proximity of lots of screened unbalanced signals
make


Every dB of reduction of hum you can get from the shielded power cable,
and from the patch cords ("interconnects") helps. If you have a system
that would normally have 120dB S/N. Now, if you want to listen to AM
radio or some scratchy vinyl (because you like the programming, and it's
not available on a lower noise source), then the shielded power cord
probably won't be noticed.


Actually I think AM radio is the only place I have noticed shielded
power cords making any difference.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/
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Default Shielded mains cable

On Tue, 29 May 2007 09:42:10 +0300, "Iain Churches"
wrote:

But seriously, this cable is included with the amp as a replacement
for the standard IEC kettle cable which we use in Europe. There
was no big fuss or hype. I was interested to know what the thinking
behind it might be.


Well, it can't hurt. If you're in a high RF soup area,
it may give you a little edge. RFI problems tend to be
threshold effects, and as modern devices get noisier
and noisier (switchmode power supplies in everything,
with **** for filtering) it may come in handy someday.

Clamp-on ferrite chokes are cheap insurance too.

Perhaps they just wanted to supply a product with high perceived-
quality down to the last nut and bolt.


Sure, and why not? Everybody likes nice things. Nothing
wrong with that.

Much thanks, as always,

Chris Hornbeck
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Default Shielded mains cable



As for the house wire in the walls, "BX" armored cable would be a good
choice. The current carrying conductors inside that armor are
essentially a twisted pair, about one twist per 10cm. And around that
is the armor shield, which also has a bare conductor just under it to
maintain a low resistance continuity. It looks a lot like regular
twisted pair shielded audio signal cable used in radio stations and
such, but on steroids. So tell the electrician you want him to use BX
cable in your audio palace.



Couldn't that land him in hot water when the electrical inspector finds
out that he used BX cable instead of following the electrical code?


Of course, but there's modern equivalents to "BX" cable that are to
code. I just called it by it's informal traditional name. Think the
modern cable is called "AC", for "armored cable".


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I've no idea if it would meet your 'code' but twisted individual conductors for
the live and neutral would work very well.


The electrical inspector wouldn't like it, so you use the "BX" cable,
which happens to have the twisting already done. And it's easier to get
an electrician to use BX than it would be to convince him to twist the
wire, or cheaper if the electrician was convinced, as he'd charge a lot
for the extra time it would take.

Anyway, the power cords of the audio equipment would deserve more
attention, as that wire is physically closer to the audio signal patch
cords anyway. Just take the cord and twist the power plug many times,
and the zip cord would take on a twisted pattern. Of course it will
want to untwist, but if you hold it down (with tape or ties or such) the
plastic wire insulation will accept the twists as it will "set in" after
a few weeks. And you don't have to break out the soldering iron or even
pop the lid off the equipment to do this...
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robert casey wrote:

The twisting will do the good, not the shielding. Save money and forget the
shielding.


In which case, just twisting the 2 wire zip cord power cords on all your
audio boxes (amps, CD players, etc) would be enough.


Not totally, because there will still be some magnetic field from the wall wiring
but it should improve things.

To avoid magnetic coupling, ideally all power and signal wiring should be twisted
pairs.


Something like one
twist per 3cm should do. The cords will tend to untwist themselves at
first, but a few weeks the cord twists will "set" into the cord
insulation. This costs exactly nothing, and you don't have to break out
the soldering iron or pop the lid off anything...


We don't use that kind of 'zip cord' here in the UK. An outer jacket is required
for a mains lead for safety. As such I'm sure it would be easy to make twisted
pair power leads for use from wall socket / plugboird to equipment.

Graham


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"François Yves Le Gal" wrote:

Eeyore wrote:

I'm sick of idiot fantasists like you and their magic cables


There's no magic in proper engineering practices. Using shielded mains
cables can reduce noise, period..


You're talking audiophool myth.

I'll bet you can't substantiate such a claim with a technical description for
it.

Graham


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Chris Hornbeck wrote:

Clamp-on ferrite chokes are cheap insurance too.


And may actually do something unlike a shield. The clamp-on ferrites are
intentionally 'lossy' to as absorb some RF power.

Graham

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"Iain Churches" wrote in message
. fi
I have just be evaluating a German built tube amp
(4 pairs of EL34 in push pull parallel) It was supplied
with a mains cable, which in addition to the L, N and
Earth wires, had an external woven copper plaid
screen/shield, under the clear plastic outer cover.

This shield appears to be connected to ground at
the amp end only.

I have seen something similar in studio/broadcast
control room racks, where test equipment was built
in, and powered from an AC outlet within the same rack.
The mains leads had a screen to prevent the possibility
of AF signals affecting measurements.

But what about in the case of audio equipment
built for use in the domestic environment?
Any opinions?


Dissection of IEC power cables supplied with computers and computer displays
finds a high proportion of shields.

The purpose of this particular cutting and stripping was to obtain the basic
power cable and line plug.

If a shielded power cable improves the performance of a piece of gear, its
an indictment of the power supply of the piece of gear.

The shielded cables used with computer gear is mostly to reduce emissions,
not as a defensive strategy to improve the performance of the gear's basic
performance as a computer or display.




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"Eeyore" wrote in
message
"François Yves Le Gal" wrote:

Eeyore wrote:

I'm sick of idiot fantasists like you and their magic
cables


There's no magic in proper engineering practices. Using
shielded mains cables can reduce noise, period..


You're talking audiophool myth.


Or, poorly-designed audio gear. This can be a problem with equipment
designed by the sorts of incomptents that ply the audio high end consumer
market.

I'll bet you can't substantiate such a claim with a technical description
for it.


There's been a lot of weirdness in high end audio gear - power amps that
burned down people's houses, DACs that were highly dependent on some
specific properties of the input cables, power amps that were highly
dependent on the use of certain speaker cables, etc. Most knowlegable people
would call this bad design, but "any difference is perceived as an
improvement" is a common among high end audiophiles and reviewers. IOW how
many reviews have suggested that a piece of gear that was inordinately
sensitive to odd properties of cable was "highly revealing of quality
differences in cables"?


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"John Byrns" wrote in message

In article
k.net,
robert casey wrote:


But what about in the case of audio equipment
built for use in the domestic environment?
Any opinions?


It would help to reduce stray electrostatic 60Hz hum
fields from invading audio patch cords. Belden makes
shielded IEC computer power cords with shielding, Sun
Microsystems used them on their workstations.


I hated those, they were way too stiff, and for some
reason we had barrels and barrels of extras, I can't
remember how that came about, they must have shipped 4 or
5 with every work station.

As for the house wire in the walls, "BX" armored cable
would be a good choice. The current carrying conductors
inside that armor are essentially a twisted pair, about
one twist per 10cm. And around that is the armor
shield, which also has a bare conductor just under it to
maintain a low resistance continuity. It looks a lot
like regular twisted pair shielded audio signal cable
used in radio stations and such, but on steroids. So
tell the electrician you want him to use BX cable in
your audio palace.


Couldn't that land him in hot water when the electrical
inspector finds out that he used BX cable instead of
following the electrical code?


Where is BX not code?


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Arny Krueger wrote:

"Eeyore" wrote
"François Yves Le Gal" wrote:
Eeyore wrote:

I'm sick of idiot fantasists like you and their magic
cables

There's no magic in proper engineering practices. Using
shielded mains cables can reduce noise, period..


You're talking audiophool myth.


Or, poorly-designed audio gear. This can be a problem with equipment
designed by the sorts of incomptents that ply the audio high end consumer
market.

I'll bet you can't substantiate such a claim with a technical description
for it.


There's been a lot of weirdness in high end audio gear - power amps that
burned down people's houses,


Instability maybe causing circuit burn-up compounded by failure to apply
well-known international standards for product safety that ensure fires won't
happen ?


DACs that were highly dependent on some
specific properties of the input cables


Doubless the absence of proper signal buffering / conditioning. Maybe a
misguided attempt to avoid 'upsetting the sound' by passing a digital signal
through an extra buffer stage in some bizarre analogy with analogue signals ?


, power amps that were highly dependent on the use of certain speaker cables,
etc.


Ah yes. Like the Naim amps that can't tolerate cable capacitance. Pure bad
design.


Most knowlegable people would call this bad design, but "any difference is
perceived as an improvement"


How they know it's an *IMPROVEMENT* is what always amuses me !


is a common among high end audiophiles and reviewers. IOW how
many reviews have suggested that a piece of gear that was inordinately
sensitive to odd properties of cable was "highly revealing of quality
differences in cables"?


It's certainly highly revealing of bad design !

Graham


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John Byrns John Byrns is offline
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Default Shielded mains cable

In article ,
"Arny Krueger" wrote:

"John Byrns" wrote in message

In article
k.net,
robert casey wrote:


But what about in the case of audio equipment
built for use in the domestic environment?
Any opinions?


It would help to reduce stray electrostatic 60Hz hum
fields from invading audio patch cords. Belden makes
shielded IEC computer power cords with shielding, Sun
Microsystems used them on their workstations.


I hated those, they were way too stiff, and for some
reason we had barrels and barrels of extras, I can't
remember how that came about, they must have shipped 4 or
5 with every work station.

As for the house wire in the walls, "BX" armored cable
would be a good choice. The current carrying conductors
inside that armor are essentially a twisted pair, about
one twist per 10cm. And around that is the armor
shield, which also has a bare conductor just under it to
maintain a low resistance continuity. It looks a lot
like regular twisted pair shielded audio signal cable
used in radio stations and such, but on steroids. So
tell the electrician you want him to use BX cable in
your audio palace.


Couldn't that land him in hot water when the electrical
inspector finds out that he used BX cable instead of
following the electrical code?


Where is BX not code?


Cook County Illinois for one.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/
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Default Shielded mains cable

"Eeyore" wrote in
message
Arny Krueger wrote:

"Eeyore" wrote
"François Yves Le Gal" wrote:
Eeyore wrote:

I'm sick of idiot fantasists like you and their magic
cables

There's no magic in proper engineering practices. Using
shielded mains cables can reduce noise, period..


You're talking audiophool myth.


Or, poorly-designed audio gear. This can be a problem
with equipment designed by the sorts of incomptents that
ply the audio high end consumer market.

I'll bet you can't substantiate such a claim with a
technical description for it.


There's been a lot of weirdness in high end audio gear -
power amps that burned down people's houses,


Instability maybe causing circuit burn-up compounded by
failure to apply well-known international standards for
product safety that ensure fires won't happen ?


The sort of fuzzy thinking that leads to a lot of so-called advances more
common in high end audio tends to lead there...

DACs that were highly dependent on some
specific properties of the input cables


Doubless the absence of proper signal buffering /
conditioning.


Something like that. There was a perception that the usual kinds of signal
processing would degrade the recovered audio. Self-verification based on
sighted evaluations, and like that.

Maybe a misguided attempt to avoid
'upsetting the sound' by passing a digital signal
through an extra buffer stage in some bizarre analogy
with analogue signals ?


Yup.

, power amps that were highly dependent on the use of
certain speaker cables, etc.


Ah yes. Like the Naim amps that can't tolerate cable
capacitance. Pure bad design.


Yup.


Most knowlegable people would call this bad design, but
"any difference is perceived as an improvement"


How they know it's an *IMPROVEMENT* is what always amuses
me !


Note that many of these *IMPROVERMENT(s)* are said to help performance in
ways that befuddle standard measurements and bias-controlled listening
tests.

is a common among high end audiophiles and reviewers.
IOW how
many reviews have suggested that a piece of gear that
was inordinately sensitive to odd properties of cable
was "highly revealing of quality differences in cables"?


It's certainly highly revealing of bad design !


Agreed.

Justice may be over-served when fuzzy thinking leads to destruction of
property.





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GregS GregS is offline
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Default Shielded mains cable

In article , "Arny Krueger" wrote:
"Iain Churches" wrote in message
.fi
I have just be evaluating a German built tube amp
(4 pairs of EL34 in push pull parallel) It was supplied
with a mains cable, which in addition to the L, N and
Earth wires, had an external woven copper plaid
screen/shield, under the clear plastic outer cover.

This shield appears to be connected to ground at
the amp end only.

I have seen something similar in studio/broadcast
control room racks, where test equipment was built
in, and powered from an AC outlet within the same rack.
The mains leads had a screen to prevent the possibility
of AF signals affecting measurements.

But what about in the case of audio equipment
built for use in the domestic environment?
Any opinions?



The IEC cables I have looked at, have the shields connected to ground on the front
end plug side, and have no connection on the other. A cord could have the shield
connected on the other end, but whatever produces less noise is preffered.

greg


Dissection of IEC power cables supplied with computers and computer displays
finds a high proportion of shields.

The purpose of this particular cutting and stripping was to obtain the basic
power cable and line plug.

If a shielded power cable improves the performance of a piece of gear, its
an indictment of the power supply of the piece of gear.

The shielded cables used with computer gear is mostly to reduce emissions,
not as a defensive strategy to improve the performance of the gear's basic
performance as a computer or display.


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Arny Krueger Arny Krueger is offline
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Default Shielded mains cable

"John Byrns" wrote in message

In article ,
"Arny Krueger" wrote:

"John Byrns" wrote in message

In article
k.net,
robert casey wrote:


But what about in the case of audio equipment
built for use in the domestic environment?
Any opinions?


It would help to reduce stray electrostatic 60Hz hum
fields from invading audio patch cords. Belden makes
shielded IEC computer power cords with shielding, Sun
Microsystems used them on their workstations.

I hated those, they were way too stiff, and for some
reason we had barrels and barrels of extras, I can't
remember how that came about, they must have shipped 4
or 5 with every work station.

As for the house wire in the walls, "BX" armored cable
would be a good choice. The current carrying
conductors inside that armor are essentially a twisted
pair, about one twist per 10cm. And around that is
the armor shield, which also has a bare conductor just
under it to maintain a low resistance continuity. It
looks a lot like regular twisted pair shielded audio
signal cable used in radio stations and such, but on
steroids. So tell the electrician you want him to use
BX cable in your audio palace.

Couldn't that land him in hot water when the electrical
inspector finds out that he used BX cable instead of
following the electrical code?


Where is BX not code?


Cook County Illinois for one.


I'm under the impression that they recently changed that to allow at least
limited lengths.


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John Byrns John Byrns is offline
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Default Shielded mains cable

In article ,
"Arny Krueger" wrote:

"John Byrns" wrote in message

In article ,
"Arny Krueger" wrote:

"John Byrns" wrote in message

In article
k.net,
robert casey wrote:


But what about in the case of audio equipment
built for use in the domestic environment?
Any opinions?


It would help to reduce stray electrostatic 60Hz hum
fields from invading audio patch cords. Belden makes
shielded IEC computer power cords with shielding, Sun
Microsystems used them on their workstations.

I hated those, they were way too stiff, and for some
reason we had barrels and barrels of extras, I can't
remember how that came about, they must have shipped 4
or 5 with every work station.

As for the house wire in the walls, "BX" armored cable
would be a good choice. The current carrying
conductors inside that armor are essentially a twisted
pair, about one twist per 10cm. And around that is
the armor shield, which also has a bare conductor just
under it to maintain a low resistance continuity. It
looks a lot like regular twisted pair shielded audio
signal cable used in radio stations and such, but on
steroids. So tell the electrician you want him to use
BX cable in your audio palace.

Couldn't that land him in hot water when the electrical
inspector finds out that he used BX cable instead of
following the electrical code?

Where is BX not code?


Cook County Illinois for one.


I'm under the impression that they recently changed that to allow at least
limited lengths.


That may very well be, I can't claim to be following this issue closely,
in any case I believe short "whips" of armored cable to connect
equipment have been allowed for some time, if not forever.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/
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Eeyore Eeyore is offline
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Default Shielded mains cable



GregS wrote:

The IEC cables I have looked at, have the shields connected to ground on the front end plug side, and
have no connection on the other. A cord could have the shield connected on the other end, but
whatever produces less noise is preffered.


They will make no difference at all unless of course you believe they will, in which case you're doomed
also to buying 'one-way',cable upgrades and the like too.

Graham

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Iain Churches Iain Churches is offline
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Default Shielded mains cable


"François Yves Le Gal" wrote in message
...
On Wed, 30 May 2007 04:36:02 GMT, Eeyore
wrote:

You're talking audiophool myth.


Yeah, sure, whatever you say.

I wonder if Arny can explain why companies like
Marconi Electronics, and Racal UK use shielded
mains cables on their equipment. These are not
firms with a "snake oil reputation" but suppliers of
mil.spec test gear to the British Govt and NATO,
so in this instance his "audiophool myth" argument
cannot be used. Is there something else?

Iain





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Default Shielded mains cable


"Eeyore" wrote in message
...


GregS wrote:

The IEC cables I have looked at, have the shields connected to ground on
the front end plug side, and
have no connection on the other. A cord could have the shield connected
on the other end, but
whatever produces less noise is preffered.


They will make no difference at all unless of course you believe they
will, in which case you're doomed
also to buying 'one-way',cable upgrades and the like too.


The IEC shielded cables I have seen have the screen connected at
the equipment end. I am told that quite a lot of Marconi and also
Racal test equipment had shielded mains cables. I have a mic preamp
by JEC Electronics that has one also. So can there be something in it?
Marconi Electronics and Racal are not exactly known for snake oil products.

In the case of the German power amp, as the mains cable, plus a
set of very presentable interconnects is included in the box, and there
is no sales-hype whatsoever, except to say that high-grade cables
are supplied, I cannot see how this can be any kind of attempt at
snake oil marketing. But at the same time, I am not convinced of
any benefit either - except that of perceived quality.

Iain






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"Iain Churches" wrote in message
i.fi
"François Yves Le Gal" wrote in
message ...


On Wed, 30 May 2007 04:36:02 GMT, Eeyore
wrote:


You're talking audiophool myth.


Yeah, sure, whatever you say.


Note Iain's problem with attribution. He's addressing something that Graham
said, as if I said it.

I wonder if Arny can explain why companies like
Marconi Electronics, and Racal UK use shielded
mains cables on their equipment.


I already did explain one sensible use of shielded power cables, but Iain
you seem to have missed it.

That's two pretty serious errors in just one post.



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"François Yves Le Gal" wrote in
message
On Tue, 29 May 2007 17:43:10 -0500, John Byrns
wrote:

Actually I think AM radio is the only place I have
noticed shielded power cords making any difference.


GSM, Wifi, you name it - all this wireless crap is a
major source of pollution nowadays.


True, but table-model AM and FM radios have been known to include an
unshelded power cord as part of their antenna system.


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On May 30, 2:18 pm, "Iain Churches" wrote:
I wonder if Arny can explain why companies like
Marconi Electronics, and Racal UK use shielded
mains cables on their equipment. These are not
firms with a "snake oil reputation" but suppliers of
mil.spec test gear to the British Govt and NATO,
so in this instance his "audiophool myth" argument
cannot be used. Is there something else?


Maybe in those cases, the shielding is not to keep noise from
radiating out of the mains cable, but to keep external noise out of
the equipment power supply?

"Mil. spec." doesn't necessarily mean better... just intended for
military applications.

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On May 30, 9:57 am, John Byrns wrote:
That may very well be, I can't claim to be following this issue closely,
in any case I believe short "whips" of armored cable to connect
equipment have been allowed for some time, if not forever.


I can't speak for unincorporated Cook County or any suburbs with their
own code, but in Chicago:

"Except where otherwise specified in this chapter and where not
subject to physical damage, listed Type AC cable with listed fittings
shall be permitted for branch circuits in concealed work fished into
existing walls or partitions where it is not possible to install
conduit.
Type AC shall be permitted for exposed work only under the following
conditions: (1) In lengths not more than 2 ft (610 mm) long at
terminations where flexibility is necessary; (2) In lengths not
greater than 6 ft (1.83 m) in accessible, but not habitable, attics
and roof spaces where installed in accordance with Section
18-27-333.12; (3) In lengths not greater than 5 ft (1.5 m), below the
basement ceiling joists where it is necessary to connect a cabinet or
junction box.
Type AC cable shall be permitted in dry locations and embedded in
plaster finish on brick or other masonry, except in damp or wet
locations. It shall be permissible to run or fish this cable in the
air voids of masonry block or tile walls where such walls are not
exposed or subject to excessive moisture or dampness."

and

"Type AC cable shall not be used where prohibited elsewhere in this
chapter, and is not permitted for the following: (1) For any
installation not permitted in Section 18-27-333.3; [above] (2) In
theaters and similar locations, or in Places of Assembly; (3) In
motion picture studios; (4) In any hazardous (classified) location;
(5) Where exposed to corrosive fumes or vapors; (6) On cranes or
hoists, except as provided in Section 18-27-610.11(c); (7) In storage
battery rooms; (8) In hoist ways or on elevators, except as provided
in Section 18-27-620.21; (9) In commercial garages; (10) Where exposed
to oil, gasoline, or any liquid or vapor having a deleterious effect
on insulation; (11) As service entrance cable. "

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