[robert casey]

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.


I've seen those power cords on stuff from Asia. Blue and brown wires
inside a jacket. It should take twisting as well, though it will want
to untwist itself until the jacket takes the "set".

[Arny Krueger]

"Theodore" wrote in message
oups.com
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?

AFAIK, companies like Marconi and Racal make equipment with switching power
supplies.

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

Mil Spec does set a fairly high standard for quality and durability.
However at times certain commercial specs have been higher than the current
most stringent Mil Spec.

[John Byrns]

In article ,
"Arny Krueger" wrote:

"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.

What you say is true of FM radios, but I have never seen it done with AM
radios, except with after market devices claiming to "Turn Your House
Wiring Into A Giant Antenna".


Regards,

John Byrns

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

[Eeyore]

"François Yves Le Gal" wrote:

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.

And power cords have absolutely ZERO to do with it.

Graham

[Eeyore]

"François Yves Le Gal" wrote:

Eeyore wrote:

You're talking audiophool myth.

Yeah, sure, whatever you say.

I do say. And I earn my living from high-performance professional audio too.

Graham

[Eeyore]

Iain Churches wrote:

"François Yves Le Gal" wrote
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 companies barely exist any more outside the defence market.

What's the relevance to audio ?

Graham

[west[_4_]]

"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?

Regards to all
Iain

The grounded on one end shield has nothing to do with AC ground. I have
often utilized this technique for sensitive medical equipment. This shield
ground is to eliminate induced RF interference in the AC line. The thing
that seems a bit odd to me is that the ground is usually placed at the
source.

Cordially,
west

[Eeyore]

west wrote:

This shield ground is to eliminate induced RF interference in the AC line.

No it isn't. You need to learn what induction is.

Graham

[Iain Churches]

"Arny Krueger" wrote in message
. ..
"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.

Arny. If I put words of wisdom into you mouth which you
did not utter, then I apologise. None of us, with the exception
of your goodself, is perfect:-))

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

I now have the answer to my question, supplied off list by an
engineer from German Broadcasting.


Cordially,
Iain

[Iain Churches]

"west" wrote in message
newsBm7i.3781$9G3.2800@trnddc07...

"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 grounded on one end shield has nothing to do with AC ground. I have
often utilized this technique for sensitive medical equipment. This shield
ground is to eliminate induced RF interference in the AC line. The thing
that seems a bit odd to me is that the ground is usually placed at the
source.


Thanks West. This amp, built in Germany, is clearly aimed at the
professional market, it is balanced throughout, and has proper
differential inputs on XLRs, and separate stepped attenuators
for each channel calibrated in dBV. Here in Europe, many
studios are using tube power amps, mic preamps and outboard
processing also.

I have had quite a few replies to my question off list by e-mail.
One guy a retired German broadcast engineer told me that it
was standard practice in analogue equipment racks for *all*
cables to be screened with RF shields. So, as you surmise,
that may be the answer.

Regards
Iain

[Iain Churches]

"Eeyore" wrote in message
...


Iain Churches wrote:

"François Yves Le Gal" wrote
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 companies barely exist any more outside the defence market.

What's the relevance to audio ?

They manufactured audio test equipment.
I was at a facility just a few days ago that had a Racal-Decca
IMD system.

[Eeyore]

Iain Churches wrote:

Here in Europe, many
studios are using tube power amps, mic preamps and outboard
processing also.

!!!

Maybe the antique 'boutique' stuff.

Graham

[Eeyore]

Iain Churches wrote:

One guy a retired German broadcast engineer told me that it
was standard practice in analogue equipment racks for *all*
cables to be screened with RF shields.

Typical Germanic overkill ! :~)

Have you ever considerd why your phone line doesn't hum appreciably despite
consisting of maybe 7 km of unscreened wire ?

Graham

[Eeyore]

Iain Churches wrote:

"Eeyore" wrote in message
Iain Churches wrote:
"François Yves Le Gal" wrote
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 companies barely exist any more outside the defence market.

What's the relevance to audio ?

They manufactured audio test equipment.
I was at a facility just a few days ago that had a Racal-Decca
IMD system.

Racal Decca ? That must be a bizarre curiosity. Racal also made magnetic tape
(Racal Zonal) on account of its business in FM instrumentation (not audio) tape
recorders.

None of these companies was notable for high spec audio test gear. They did make
general test equipment for sure but nothing to associate them specifically with
pro-audio or hi-fi.

The only UK maker of serious audio specific test gear was Radford, later to
become Wayne Kerr Radford, later still dropping the Radford.

Marconi did have a specialist 'Instruments' division based in St Albans where I
live but long gone now other than for leaving its name to the road 'Marconi
Way'. It's speciality was RF btw.

Graham

[Iain Churches]

"Eeyore" wrote in message
...


Iain Churches wrote:

Here in Europe, many
studios are using tube power amps, mic preamps and outboard
processing also.

!!!

Maybe the antique 'boutique' stuff.


Studios provide what clients ask for. Simple as that.
Market research is an important factor in any successful
business.

[Eeyore]

Iain Churches wrote:

"Eeyore" wrote
Iain Churches wrote:

Here in Europe, many
studios are using tube power amps, mic preamps and outboard
processing also.

!!!

Maybe the antique 'boutique' stuff.

Studios provide what clients ask for. Simple as that.
Market research is an important factor in any successful
business.

You don't need to do much research to know that Teletronix / Urei optical
compressors are much liked.
http://www.barryrudolph.com/mix/bombfactory.html

These days you can get them as digital plug-ins though.

[Iain Churches]

"Eeyore" wrote in message
...


Iain Churches wrote:

"Eeyore" wrote in message
Iain Churches wrote:
"François Yves Le Gal" wrote
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 companies barely exist any more outside the defence market.

What's the relevance to audio ?

They manufactured audio test equipment.
I was at a facility just a few days ago that had a Racal-Decca
IMD system.

Racal Decca ? That must be a bizarre curiosity. Racal also made magnetic
tape
(Racal Zonal) on account of its business in FM instrumentation (not audio)
tape
recorders.

They actually made quite a range of equipment, under Racal, Racal Dana, and
Racal Decca names. Remember that Decca was first and foremost an electronics
group, Decca Radar, and Decca Navigator

None of these companies was notable for high spec audio test gear. They
did make
general test equipment for sure but nothing to associate them specifically
with
pro-audio or hi-fi.

One used to see lots of Marconi and Racal, plus of course Wayne Kerr in
studio workshops. Another UK maker, Ferrograph, had an RTS that was
ubiquitous.

[Iain Churches]

"Eeyore" wrote in message
...


Iain Churches wrote:

"Eeyore" wrote
Iain Churches wrote:

Here in Europe, many
studios are using tube power amps, mic preamps and outboard
processing also.

!!!

Maybe the antique 'boutique' stuff.

Studios provide what clients ask for. Simple as that.
Market research is an important factor in any successful
business.

You don't need to do much research to know that Teletronix / Urei optical
compressors are much liked.
http://www.barryrudolph.com/mix/bombfactory.html

These days you can get them as digital plug-ins though.

Many singers turn up at the studio with their own compressor
with chinagraph pencil marks on the dial for their "magic" settings.
Some even bring their own mic. You see beautifully kept Neumann
47s (original) quite often.

[Eeyore]

Iain Churches wrote:

"Eeyore" wrote
Iain Churches wrote:
"Eeyore" wrote
Iain Churches wrote:
"François Yves Le Gal" wrote
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 companies barely exist any more outside the defence market.

What's the relevance to audio ?

They manufactured audio test equipment.
I was at a facility just a few days ago that had a Racal-Decca
IMD system.

Racal Decca ? That must be a bizarre curiosity. Racal also made magnetic
tape (Racal Zonal) on account of its business in FM instrumentation (not
audio)
tape recorders.

They actually made quite a range of equipment, under Racal, Racal Dana, and
Racal Decca names. Remember that Decca was first and foremost an electronics
group, Decca Radar, and Decca Navigator

For sure. As was EMI.


None of these companies was notable for high spec audio test gear. They
did make general test equipment for sure but nothing to associate them
specifically with pro-audio or hi-fi.

One used to see lots of Marconi and Racal,

I never have myself. A slightly different era perhaps ?


plus of course Wayne Kerr in studio workshops. Another UK maker, Ferrograph,
had an RTS that was ubiquitous.

I'll likeley be using a Ferrograph RTS later today actually. It needs an
overhaul but is still basically functional.

Graham

[Iain Churches]

"Eeyore" wrote in message
...


Iain Churches wrote:

"Eeyore" wrote
Iain Churches wrote:
"Eeyore" wrote
Iain Churches wrote:
"François Yves Le Gal" wrote
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 companies barely exist any more outside the defence market.

What's the relevance to audio ?

They manufactured audio test equipment.
I was at a facility just a few days ago that had a Racal-Decca
IMD system.

Racal Decca ? That must be a bizarre curiosity. Racal also made
magnetic
tape (Racal Zonal) on account of its business in FM instrumentation
(not
audio)
tape recorders.

They actually made quite a range of equipment, under Racal, Racal Dana,
and
Racal Decca names. Remember that Decca was first and foremost an
electronics
group, Decca Radar, and Decca Navigator

For sure. As was EMI.


None of these companies was notable for high spec audio test gear. They
did make general test equipment for sure but nothing to associate them

specifically with pro-audio or hi-fi.

One used to see lots of Marconi and Racal,

I never have myself. A slightly different era perhaps ?

Am I showing my age? :-)))


plus of course Wayne Kerr in studio workshops. Another UK maker,
Ferrograph,
had an RTS that was ubiquitous.

I'll likeley be using a Ferrograph RTS later today actually. It needs an
overhaul but is still basically functional.

It's a useful instrument, especially with the additional ATU.
I have a pristine one, plus a spare SIFAM meter still in its original box.
Canford Audio used to be spares agent for Ferrograph, but sadly no longer.
I have a set of schematics which I would be happy to scan for you if
required

Regards
Iain

[Mike Gilmour]

"Iain Churches" wrote in message
i.fi...

"Eeyore" wrote in message
...


Iain Churches wrote:

"Eeyore" wrote in message
Iain Churches wrote:
"François Yves Le Gal" wrote
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 companies barely exist any more outside the defence market.

What's the relevance to audio ?

They manufactured audio test equipment.
I was at a facility just a few days ago that had a Racal-Decca
IMD system.

Racal Decca ? That must be a bizarre curiosity. Racal also made magnetic
tape
(Racal Zonal) on account of its business in FM instrumentation (not
audio) tape
recorders.

They actually made quite a range of equipment, under Racal, Racal Dana,
and
Racal Decca names. Remember that Decca was first and foremost an
electronics
group, Decca Radar, and Decca Navigator

Indeed Iain, I recall attending a two week course in Croydon on Decca radar
and sailing on many ships so equipped. The Decca Navigator of course was
eventually made redundant by GPS but I recall their models right through
valve to solid state along with the nav charts marked with Decca lanes. Used
also in aviation.


None of these companies was notable for high spec audio test gear. They
did make
general test equipment for sure but nothing to associate them
specifically with
pro-audio or hi-fi.

One used to see lots of Marconi and Racal, plus of course Wayne Kerr in
studio workshops. Another UK maker, Ferrograph, had an RTS that was
ubiquitous.

[John Byrns]

In article ,
Fran?ois Yves Le Gal wrote:

On Thu, 31 May 2007 06:14:11 GMT, Eeyore
wrote:

Have you ever considerd why your phone line doesn't hum appreciably despite
consisting of maybe 7 km of unscreened wire ?

A phone line uses multiple twisted pairs for it's copper segments. Twisted
pairs are very efficient when it comes to reject common mode noise, with
typical attenuations of 40 dB or more.

Land line bandwith is limited to app. 300 to 4,000 Hz for voice, with
typically a second order passband transfer function. Couplers, speakers and
all components are similarly bandwith limited.

Mains-induced hum has a fundamental at 50 or 60 Hz, 5 or 6 octaves below the
- 3 dB point. Any hum will be typically at -90 dB or more below signal.

"5 or 6 octaves below the - 3 dB point"?


Regards,

John Byrns

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

[Arny Krueger]

"François Yves Le Gal" wrote in
message
On Wed, 30 May 2007 21:34:53 GMT, Eeyore
wrote:

And power cords have absolutely ZERO to do with it.

Yeah sure, using a shielded/ferrite coated mains cable in
RFI-rich environments (as well as other forms of
filtering in the PS) is terminal audiophilia.

The point is that good equipment is supposed to, and generally does deal
with RFI-rich environments.

[Arny Krueger]

"John Byrns" wrote in message

In article ,
Fran?ois Yves Le Gal wrote:

On Thu, 31 May 2007 06:14:11 GMT, Eeyore
wrote:

Have you ever considerd why your phone line doesn't hum
appreciably despite consisting of maybe 7 km of
unscreened wire ?

A phone line uses multiple twisted pairs for it's copper
segments. Twisted pairs are very efficient when it comes
to reject common mode noise, with typical attenuations
of 40 dB or more.

Land line bandwith is limited to app. 300 to 4,000 Hz
for voice, with typically a second order passband
transfer function. Couplers, speakers and all components
are similarly bandwith limited.

Mains-induced hum has a fundamental at 50 or 60 Hz, 5 or
6 octaves below the - 3 dB point. Any hum will be
typically at -90 dB or more below signal.

"5 or 6 octaves below the - 3 dB point"?

Hmm I presume that 300 Hz would be the -3 dB point.

150 Hz = 1 octave down
75 Hz = 2 octaves down

score!

[jim Gregory]

We -have- digressed from debating fancy, screened mains jumpers...
Telephone wire...
It's run as twisted pairs as part of a sheathed multipair in ground or sea
(and maybe overhead via poles), while the phone instrument is made as a
hybrid-coil balanced equipment with reasonable CMRR, and, quite
importantly, voice comms response cuts off below 300Hz. Hum can be 50-100,
60-120Hz, at least an octave out of band.

"Eeyore" wrote in message
...


Iain Churches wrote:

One guy a retired German broadcast engineer told me that it
was standard practice in analogue equipment racks for *all*
cables to be screened with RF shields.

Typical Germanic overkill ! :~)

Have you ever considerd why your phone line doesn't hum appreciably
despite
consisting of maybe 7 km of unscreened wire ?

Graham

[Arny Krueger]

"François Yves Le Gal" wrote in
message
On Thu, 31 May 2007 09:14:09 -0400, "Arny Krueger"
wrote:

The point is that good equipment is supposed to, and
generally does deal with RFI-rich environments.

Rule number one : never suppose anything.

No, rule number one: Test every hypothesis.

[Peter Wieck]

On May 29, 9:57 am, Eeyore
wrote:
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

Without stepping into the essential idiocy of a meter or two of fancy
wiring altering the fundamental quality of power sourced from miles
away through several transforms, switches and many miles of wire...

A shielded mains cable *might* be useful against heavy transients from
equipment nearby, *might* be useful against noise from switching power-
supplies, *might* be useful against local rF sources (and if you
discount this, you have never experienced CB interference from
truckers with massive (and illegal) linear amps on their rigs).
Operative word in all cases is *might*.

I would be quite skeptical. I would pay no more for such a rig. But to
install such a rig purchasing the cable from my local supply-house and
so forth would be no more than a US$20 ordeal including the correct
NEMA plug.

Peter Wieck
Wyncote, PA

[west[_4_]]

"Eeyore" wrote in message
...


west wrote:

This shield ground is to eliminate induced RF interference in the AC
line.

No it isn't. You need to learn what induction is.

Graham

I didn't think you were the type inclined to toss out a curt diatribe.
Perhaps you need to learn the conventions of a civilized dialog.

west

[Peter Wieck]

On May 30, 6:08 pm, "west" 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?

Regards to all
Iain

The grounded on one end shield has nothing to do with AC ground. I have
often utilized this technique for sensitive medical equipment. This shield
ground is to eliminate induced RF interference in the AC line. The thing
that seems a bit odd to me is that the ground is usually placed at the
source.

Cordially,
west



- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

How would a few feet of shielding on an AC line overcome the same rF
interference generated on the mains lines up to the receptacle? I
could see such precautions in hospital conditions having to do with
those mains being shielded (either in conduit or MC) so it makes sense
to continue it to the equipment. But under most residential conditions
using PVC-insulated wire, that last meter or so is pretty useless
against rF. I did mention CB interference as a *might* in a prior
post, but that has more to do with possible rectification due to
salts-of-corrosion if the cord is removable and not hard-wired; and
that CB can be as many as several watts at very short range. Hence the
*might*. Otherwise, most equipment cases are pretty good faraday
boxes, so shielding (or not) on any bit of line-voltage wiring outside
the case will be of very little value as the leakage opportunities are
rife beyond that magic meter.

In your last several posts, you have asked for a "name", while
carefully not posting your own (remember Dan?) and then lectured on
civilized discourse. It would seem that your skin is a bit thin for
usenet. Just an observation.

Oh, and your name would be? Small-w-west does not quite ring true.

Peter Wieck
Wyncote, PA

[Iain Churches]

"Eeyore" wrote in message
...

The only UK maker of serious audio specific test gear was Radford, later
to
become Wayne Kerr Radford, later still dropping the Radford.

Hi Graham. I am getting indignant e.mails by the bucketfull,
People asking: "Have you never heard of Dawe Instruments, Solartron,
Pye Electronics, Levell UK, Farnell, Feedback Electronics etc etc"

Anyone would think it was I who made the above statement:-)


Regards
Iain

[Eeyore]

"François Yves Le Gal" wrote:

Eeyore wrote:

And power cords have absolutely ZERO to do with it.

Yeah sure, using a shielded/ferrite coated mains cable in RFI-rich
environments (as well as other forms of filtering in the PS) is terminal
audiophilia.

The ferrite has a specific purpose. It's normally used on the leads of equipment
with high emissions to reduce those emissions.

Shielded power cables for audio equipment are just a fad for those with no
sense.

Graham

[Eeyore]

Eeyore wrote:

Have you ever considerd why your phone line doesn't hum appreciably despite
consisting of maybe 7 km of unscreened wire ?

A phone line uses multiple twisted pairs for it's copper segments. Twisted
pairs are very efficient when it comes to reject common mode noise, with
typical attenuations of 40 dB or more.

More like 90dB !


Land line bandwith is limited to app. 300 to 4,000 Hz for voice, with
typically a second order passband transfer function. Couplers, speakers and
all components are similarly bandwith limited.

An artificial restriction based on the exchange equipment and intended use.
Local loop twisted pairs are used for ADSL for example with frequencies up to 1
MHz.


Graham

[Eeyore]

Peter Wieck wrote:

A shielded mains cable *might* be useful against heavy transients from
equipment nearby,

How ?

*might* be useful against noise from switching power-
supplies, *might* be useful against local rF sources (and if you
discount this, you have never experienced CB interference from
truckers with massive (and illegal) linear amps on their rigs).
Operative word in all cases is *might*.

It'll do nothing about the unscreened cable in the wall so will have effectively
zero impact.


Graham

[Eeyore]

west wrote:

"Eeyore" wrote
west wrote:

This shield ground is to eliminate induced RF interference in the AC
line.

No it isn't. You need to learn what induction is.

I didn't think you were the type inclined to toss out a curt diatribe.
Perhaps you need to learn the conventions of a civilized dialog.

You need to learn the conventions of not talking out of your rectum.

Graham

[John Byrns]

In article ,
Eeyore wrote:

Eeyore wrote:

Land line bandwith is limited to app. 300 to 4,000 Hz for voice, with
typically a second order passband transfer function. Couplers, speakers and
all components are similarly bandwith limited.

An artificial restriction based on the exchange equipment and intended use.
Local loop twisted pairs are used for ADSL for example with frequencies up
to 1 MHz.

But what is the SNR at 1 MHz vs. 1 kHz?


Regards,

John Byrns

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

[Peter Wieck]

On May 31, 4:36 pm, Eeyore
wrote:
Peter Wieck wrote:
A shielded mains cable *might* be useful against heavy transients from
equipment nearby,

How ?

See the answer below.

It'll do nothing about the unscreened cable in the wall so will have effectively
zero impact.

Yes, of course. But....

If the mains cabling is shielded (around here, Romex is suddenly
getting to the same cost as MC cable due to the relatively high cost
of vinyl), then a shielded mains cable will carry that all the way to
the unit. The typical "modern" house is a morass of noise transients
as appliances get cheaper and cheaper, badly executed dimmers and
poorly shielded CFL ballasts, super-cheap ignition transformers and
all sorts of other stuff is becoming more and more common. And as
pilotless appliances are mandated in nearly all areas these days, the
race for the bottom will make unshielded spark coils more and more
common.

And if a heavy transient nearby cannot induce through the shielding as
it is take all the way to the Panel (and beyond if you have examined
SE cable at any point) *ass*uming all sorts of other conditions, then
that may be useful as well.

Once again, I would not pay extra for such treatment. But I can
imagine rare conditions where it *might* be useful.

Peter Wieck
Wyncote, PA

[Eeyore]

Iain Churches wrote:

"Eeyore" wrote

The only UK maker of serious audio specific test gear was Radford, later
to become Wayne Kerr Radford, later still dropping the Radford.

Hi Graham. I am getting indignant e.mails by the bucketfull,
People asking: "Have you never heard of Dawe Instruments, Solartron,
Pye Electronics, Levell UK, Farnell, Feedback Electronics etc etc"

Anyone would think it was I who made the above statement:-)

LOL ! Well, I even still have some Levell kit myself (oscillator and
microvoltmeter) but I never considered it to be audio specific nor especially
well made either as it happens.

About 36 yrs ago I did actually buy a Feedback Instruments sweep generator for
Studiomaster's R&D lab. In those days before modern automated test gear it was
quite handy to look a frequency response with.

I have however failed to mention Bruel and Kjaer. I still have a chart recorder
of theirs here ! Leader Instruments made a kind of asian knock-off of it too
with inbuilt oscillator as a self-contained response measurement set.

Sound Technology should have a mention too. They made some very fine test kit
specifically for audio but seemingly later vanished without trace.

Then again there was Tektronix's excellent SG505 sig-gen and matching AA501
analyser. Designed by the same guys who went on to become Audio Precision.
Hewlett Packard had an all-in-one audio sig-gen and analyser which I once used
for a couple of weeks. It was OK but I wasn't especially keen on it.

Audio Precision is still my fave by a long way, although I have some ideas to
design a remote control surface for the Prism Sound analyser that would make it
more user friendly.

Lastly, a word of loathing for Neutrik's A2. God, I *HATE* that POS. It seems
they took the UK made Technical Projects self-contained test set and buggered it
up !

Graham

[Eeyore]

John Byrns wrote:

Eeyore wrote:

Eeyore wrote:

Land line bandwith is limited to app. 300 to 4,000 Hz for voice, with
typically a second order passband transfer function. Couplers, speakers and
all components are similarly bandwith limited.

An artificial restriction based on the exchange equipment and intended use.
Local loop twisted pairs are used for ADSL for example with frequencies up
to 1 MHz.

But what is the SNR at 1 MHz vs. 1 kHz?

Quite low !

It actually might be half-decent if the telephone wires were twisted more tightly
though. After all Cat 5 UTP works rather well doesn't it ?


Graham

[John Byrns]

In article ,
Eeyore wrote:

John Byrns wrote:

Eeyore wrote:

Eeyore wrote:

Land line bandwith is limited to app. 300 to 4,000 Hz for voice, with
typically a second order passband transfer function. Couplers, speakers
and
all components are similarly bandwith limited.

An artificial restriction based on the exchange equipment and intended
use.
Local loop twisted pairs are used for ADSL for example with frequencies
up
to 1 MHz.

But what is the SNR at 1 MHz vs. 1 kHz?

Quite low !

It actually might be half-decent if the telephone wires were twisted more
tightly
though. After all Cat 5 UTP works rather well doesn't it ?

I think that is a somewhat abbreviated answer that fails to address the
issue completely.

I also meant to ask why DSL doesn't have the same range as voice
transmitted from the exchange over the same pair?


Regards,

John Byrns

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

[Eeyore]

John Byrns wrote:

Eeyore wrote:
John Byrns wrote:
Eeyore wrote:
Eeyore wrote:

Land line bandwith is limited to app. 300 to 4,000 Hz for voice, with
typically a second order passband transfer function. Couplers, speakers
and all components are similarly bandwith limited.

An artificial restriction based on the exchange equipment and intended
use. Local loop twisted pairs are used for ADSL for example with
frequencies up to 1 MHz.

But what is the SNR at 1 MHz vs. 1 kHz?

Quite low !

It actually might be half-decent if the telephone wires were twisted more
tightly though. After all Cat 5 UTP works rather well doesn't it ?

I think that is a somewhat abbreviated answer that fails to address the
issue completely.

I also meant to ask why DSL doesn't have the same range as voice
transmitted from the exchange over the same pair?

Because the high frequency attenuation is greater maybe ? Or the s/n ratio degrades
too fast at higher frequencies. See my comment about Cat 5 and twist rate.

Graham