Digital Cables
 

On Thu, 23 Nov 2006 09:33:03 +0000 (GMT), Jim Lesurf
wrote:


Throughout the magazine they continue to rave over magic cables. But,
to give due credit, several times they add "but see p.121 for another
opinion". I wonder if this qualification will persist in future issues?


Interesting that it is presented as "another opinion". i.e. Not presented
on the basis that actual evidence either fails to support, or contradicts
much of what they print. Or that they have no idea how to run a comparison
that might give reliable results. :-)


The editor had rather nice tits.

Digital Cables
 

Serge Auckland wrote:

I don't think that anybody that knows how digital audio is transmitted
would believe that *any* digital cable will make a difference. AES-EBU
and SP-DIF signals are incredibly rugged, and provided the cable is of
75 ohms impedance, what it's made of and how constructed will have *no*
effect on the signal transmitted.

Can some kind soul please tell me what the impedance of a "normal"
analogue phono-phono cable is?

Digital Cables
 

In article , Anton
Gijsen wrote:
Serge Auckland wrote:

I don't think that anybody that knows how digital audio is transmitted
would believe that *any* digital cable will make a difference.
AES-EBU and SP-DIF signals are incredibly rugged, and provided the
cable is of 75 ohms impedance, what it's made of and how constructed
will have *no* effect on the signal transmitted.

Can some kind soul please tell me what the impedance of a "normal"
analogue phono-phono cable is?

Not really, since it will vary from one example to another. Domestic audio
co-ax is not specified in terms of its impedance as that isn't normally
relevant. What *may* matter is the value for its capacitance per metre.
This is quoted in some catalogues - e.g. by Maplin. But tends not to be
mentioned in magazine 'reviews' sic of cables.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Digital Cables
 

Anton Gijsen wrote:
Serge Auckland wrote:

I don't think that anybody that knows how digital audio is transmitted
would believe that *any* digital cable will make a difference. AES-EBU
and SP-DIF signals are incredibly rugged, and provided the cable is of
75 ohms impedance, what it's made of and how constructed will have
*no* effect on the signal transmitted.

Can some kind soul please tell me what the impedance of a "normal"
analogue phono-phono cable is?

It really all depends on the construction of the cable. If it's coaxial
with a single stranded or solid central core, dielectric to an outer
screen, it will most likely be in the region of 40-100 ohms. If it's a
twisted pair with an outer screen then perhaps 80-130 ohms.
The exact value will depend on the dimensions, dielectric properties of
the insulations, method of construction etc. so it's not really possible
to define a "normal" cable, but in my experience, albeit of many years
ago, these were the typical figures I recall.

S.

Digital Cables
 

Serge Auckland wrote:

Anton Gijsen wrote:

Serge Auckland wrote:

I don't think that anybody that knows how digital audio is
transmitted would believe that *any* digital cable will make a
difference. AES-EBU and SP-DIF signals are incredibly rugged, and
provided the cable is of 75 ohms impedance, what it's made of and how
constructed will have *no* effect on the signal transmitted.


Can some kind soul please tell me what the impedance of a "normal"
analogue phono-phono cable is?


It really all depends on the construction of the cable. If it's coaxial
with a single stranded or solid central core, dielectric to an outer
screen, it will most likely be in the region of 40-100 ohms. If it's a
twisted pair with an outer screen then perhaps 80-130 ohms.
The exact value will depend on the dimensions, dielectric properties of
the insulations, method of construction etc. so it's not really possible
to define a "normal" cable, but in my experience, albeit of many years
ago, these were the typical figures I recall.

The characteristic impedance doesn't apply at audio frequencies,
so you can just consider the CLR values.

--
Eiron.

Digital Cables
 

In article , Serge Auckland
wrote:


I have been a monthly reader of Hi-Fi News since it had a yellow border,
and its current incarnation may well see me not renewing my
subscription. Apart from the occasional sensible article (a recent one
by a certain Mr Lesurf included), they now run so-called articles by
Russ Andrews promoting fairy-dust, have dropped John Crabbe's column,
have long since dropped a regular Radio article,

FWIW I also regret the dissapearance of John Crabbe as well as 'radio'.
Indeed, I feel that HFN would benefit from more regular info on both radio
and recording. I'd also love to see more (informative) articles on
classic/old equipment. In particular I'd love to see reprints of some of
the technical articles. e.,g.s including the Jim Sugden articles on his
class A amp, and the Radford series on his valve amps. In both cases these
gave considerable design details. Past articles by all kinds of
knowledgeable folk like Stan Kelly, etc, also spring to mind...


have the ridiculous Hi-Fi Doctor dispensing plain wrong advice and their
new tabloid style with colour splashes everywhere and wacky picture
positioning makes me feel seasick.

In this month's issue there is an edited-down version of an article on
'clipping on CD'. There was a last-min panic with this as the deputy editor
urgently needed some 'quotes/facts' to put into the three 'blobs' on the
final page. The layout was pre-fixed, so something for the blobs *had* be
to found. Must admit that this seemed to me like the cart driving the
horse, and simply gave the poor over-worked deputy editor more work to do.
However, suitable wordings were duly found.

[BTW since on the topic. The editorial comment at the end of the of the
article re the programs used for the article is incorrect. All the results
in the article stem from programs I wrote and used. But there *is* also now
a 'windows' equivalent which Keith Howard kindly wrote as I am useless at
programming for windows boxen. :-) So if you have a windows machine you
can download and use Keith's program to get analysis results for your own
CDs similar to those in the article. ]


Even the outrageous Ken Kessler has gone. I seldom agreed with Kessler's
writings, but at least he *can* write, and was amusing.

I confess that I do not miss KK. :-)

...but I'd much prefer John Crabbe to Russ Andrews!

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Digital Cables
 

In article ,
Anton Gijsen wrote:
I don't think that anybody that knows how digital audio is transmitted
would believe that *any* digital cable will make a difference.
AES-EBU and SP-DIF signals are incredibly rugged, and provided the
cable is of 75 ohms impedance, what it's made of and how constructed
will have *no* effect on the signal transmitted.

Can some kind soul please tell me what the impedance of a "normal"
analogue phono-phono cable is?

It doesn't matter since domestic audio connections aren't matched. They
will be typically something like a 50 ohm output and a 50 kohm input.
Unlike video which is usually 75 ohms in and out.

However, most co-ax cable used for phono circuits will be centred around
75 ohms.

--
*Oh, what a tangled website we weave when first we practice *

Dave Plowman London SW
To e-mail, change noise into sound.

Digital Cables
 

Eiron wrote:
Serge Auckland wrote:

Anton Gijsen wrote:

Serge Auckland wrote:

I don't think that anybody that knows how digital audio is
transmitted would believe that *any* digital cable will make a
difference. AES-EBU and SP-DIF signals are incredibly rugged, and
provided the cable is of 75 ohms impedance, what it's made of and
how constructed will have *no* effect on the signal transmitted.


Can some kind soul please tell me what the impedance of a "normal"
analogue phono-phono cable is?


It really all depends on the construction of the cable. If it's
coaxial with a single stranded or solid central core, dielectric to an
outer screen, it will most likely be in the region of 40-100 ohms. If
it's a twisted pair with an outer screen then perhaps 80-130 ohms.
The exact value will depend on the dimensions, dielectric properties
of the insulations, method of construction etc. so it's not really
possible to define a "normal" cable, but in my experience, albeit of
many years ago, these were the typical figures I recall.

The characteristic impedance doesn't apply at audio frequencies,
so you can just consider the CLR values.

A minor correction in the interest of precision: Characteristic
impedance *does* apply at all frequencies, it's just that it's
irrelevant for analogue audio frequency signals on the sort of lengths
used domestically. If you were to be setting up analogue music-lines as
the Post Office had up to a few years ago when distances could be many
hundreds of kilometres, it was certainly relevant.

S.

Digital Cables
 

Serge Auckland wrote:

Eiron wrote:

Serge Auckland wrote:

Anton Gijsen wrote:

Serge Auckland wrote:

I don't think that anybody that knows how digital audio is
transmitted would believe that *any* digital cable will make a
difference. AES-EBU and SP-DIF signals are incredibly rugged, and
provided the cable is of 75 ohms impedance, what it's made of and
how constructed will have *no* effect on the signal transmitted.



Can some kind soul please tell me what the impedance of a "normal"
analogue phono-phono cable is?



It really all depends on the construction of the cable. If it's
coaxial with a single stranded or solid central core, dielectric to
an outer screen, it will most likely be in the region of 40-100 ohms.
If it's a twisted pair with an outer screen then perhaps 80-130 ohms.
The exact value will depend on the dimensions, dielectric properties
of the insulations, method of construction etc. so it's not really
possible to define a "normal" cable, but in my experience, albeit of
many years ago, these were the typical figures I recall.


The characteristic impedance doesn't apply at audio frequencies,
so you can just consider the CLR values.

A minor correction in the interest of precision: Characteristic
impedance *does* apply at all frequencies, it's just that it's
irrelevant for analogue audio frequency signals on the sort of lengths
used domestically. If you were to be setting up analogue music-lines as
the Post Office had up to a few years ago when distances could be many
hundreds of kilometres, it was certainly relevant.

Another minor correction: The characteristic impedance of a cable
applies above its corner frequency. Below that the impedance increases
with decreasing frequency so driving and terminating resistors won't
stop reflections over a range of frequencies.

Can some kind soul please tell Anton what the impedance of a "normal"
analogue phono-phono cable is and what frequency range it applies to?

--
Eiron.

Digital Cables
 

Eiron wrote:
Serge Auckland wrote:

Eiron wrote:

Serge Auckland wrote:

Anton Gijsen wrote:

Serge Auckland wrote:

I don't think that anybody that knows how digital audio is
transmitted would believe that *any* digital cable will make a
difference. AES-EBU and SP-DIF signals are incredibly rugged, and
provided the cable is of 75 ohms impedance, what it's made of and
how constructed will have *no* effect on the signal transmitted.



Can some kind soul please tell me what the impedance of a "normal"
analogue phono-phono cable is?



It really all depends on the construction of the cable. If it's
coaxial with a single stranded or solid central core, dielectric to
an outer screen, it will most likely be in the region of 40-100
ohms. If it's a twisted pair with an outer screen then perhaps
80-130 ohms.
The exact value will depend on the dimensions, dielectric properties
of the insulations, method of construction etc. so it's not really
possible to define a "normal" cable, but in my experience, albeit of
many years ago, these were the typical figures I recall.


The characteristic impedance doesn't apply at audio frequencies,
so you can just consider the CLR values.

A minor correction in the interest of precision: Characteristic
impedance *does* apply at all frequencies, it's just that it's
irrelevant for analogue audio frequency signals on the sort of lengths
used domestically. If you were to be setting up analogue music-lines
as the Post Office had up to a few years ago when distances could be
many hundreds of kilometres, it was certainly relevant.

Another minor correction: The characteristic impedance of a cable
applies above its corner frequency. Below that the impedance increases
with decreasing frequency so driving and terminating resistors won't
stop reflections over a range of frequencies.

Right! I was wrong on this, I forgot about the lower cut-off frequency.

Can some kind soul please tell Anton what the impedance of a "normal"
analogue phono-phono cable is and what frequency range it applies to?

Impedances as above, but as to what frequency they apply above, it
depends on the capacitance and inductance characteristics of the cable.
The formula is Fc=2/2Pi x root(LC) according to my reference, where L is
the inductance/unit length and C is the capacitance /unit length.
Characteristic impedance is root (L/C) above the cut-off frequency Fc.

Trying a few typical L and C values for coax cables, I get Fc of several
MHz, so Eiron is right that not only it isn't relevant at audio
frequencies, but the characteristic impedance is way over the nominal 75
ohms (or whatever) until frequencies of several MHz are reached.


S.