Digital Coaxial cable?

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Can you use a 'regular' left or right composite cable to make a coaxial
connection or do you have to get an actual coaxial cable? I wasn't
sure if the coaxial cable was wired or made differently inside then the
audio composite cables were.

Thanks.

 

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Sseadoubleyou wrote:
> Can you use a 'regular' left or right composite cable to make a coaxial
> connection

Please explain what you mean by this? A standard sheielded audio cable?
That's a coaxial cable. "Coaxial" means that there are two conductors
that share the same axis along the length of the cable. There's the
center conductor, and the shield around it.

> I wasn't
> sure if the coaxial cable was wired or made differently inside then the
> audio composite cables were.

Depending on what you're connecting, you may need something other than
the RCA connectors that you're familiar with, if I correctly guess what
cables you're talking about. There are many coaxial connectors (as well
as cable types), of which the RCA phono plug, the most common audio
connector in consumer products, is just one.

There are all sorts of ways that a cable sold as a digital interconnect
cable might be better than your plain old RCA audio cables, but you
won't hurt anything by trying what you have avaiable. For short
lengths, just about anything will work.

 

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"Sseadoubleyou" wrote ...
> Can you use a 'regular' left or right composite cable to make a coaxial
> connection or do you have to get an actual coaxial cable? I wasn't
> sure if the coaxial cable was wired or made differently inside then the
> audio composite cables were.

You appear to believe that "composite audio cable" and "coaxial
cable" are two different things. In 99.8% of cases, they mean
exactly the same thing.

Some people may use "coaxial" to mean RF (or video) style
("RG") cable, but that is the kind of language perversion and
imprecision that is causing your confusion.

Furthermore, for most short (<4ft) consumer digital (S/PDIF)
applications, resonably decent shielded ("coaxial" or "composite"
if you will) audio cable will likely perform perfectly as well as
them most expensive botique snake-oil cable you can find.

 

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Sseadoubleyou <Sseadoubleyou@yahoo.com> wrote:
>Can you use a 'regular' left or right composite cable to make a coaxial
>connection or do you have to get an actual coaxial cable? I wasn't
>sure if the coaxial cable was wired or made differently inside then the
>audio composite cables were.

You should use a 75 ohm coaxial cable, that is designed to have a constant
impedance. Any video cable should do.

If you use a cable that isn't rated for impedance and isn't constant impedance,
it will probably work for short lengths, but then again it might not. Since
video cable is dirt cheap, just use it.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

 

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Archived from groups: rec.audio.pro (More info?)

On Thu, 22 Sep 2005 16:29:35 -0700, Sseadoubleyou wrote:

> Can you use a 'regular' left or right composite cable to make a coaxial
> connection or do you have to get an actual coaxial cable? I wasn't sure
> if the coaxial cable was wired or made differently inside then the audio
> composite cables were.

"Coaxial" means the shield wire (or "ground", or "-") wire is in the form
of a spiral or braided tube which surrounds the hot (or +) wire. It has to
do with the physical construction of the cable; it doesn't really describe
a "connection" at all (although it can describe a "connector", which has a
similar construction to a coaxial cable).

"Composite" means something made up of various parts, but I have no idea
what you intended to mean by your use of the word.

Now, the question I THINK you are asking is "Is there a difference between
the coax cable sold for digital use & regular old everyday shielded
cable?" If that's the right question, then the answer is "yes". Digital
coax (and video coax) is 75 ohm cable. It's actually more similar to the
coax that carries your cable TV signal into your house that it is to any
knid of audio cable.

As I understand it, the "75 ohm" designation means that regardless of
length (or at least within any "reasonable" length), a 75 ohm output will
still match to a 75 ohm input. It's not a measurement of the impedance
or resistance of the cable itself. This wouldn't be important for normal
analog audio, because the cable lengths are typically shorter, and the
frequencies are lower. It makes a bigger difference for video or digital,
where the frequency is much higher.

Now I'm not an EE, so hopefully if I'm way off base somebody will give us
the correct scoop.

 

[Guest]

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Agent 86 wrote:
> On Thu, 22 Sep 2005 16:29:35 -0700, Sseadoubleyou wrote:
>
>>Can you use a 'regular' left or right composite cable to make a coaxial
>>connection or do you have to get an actual coaxial cable? I wasn't sure
>>if the coaxial cable was wired or made differently inside then the audio
>>composite cables were.
>
> "Composite" means something made up of various parts, but I have no idea
> what you intended to mean by your use of the word.

I suspect that he means a cable that is intended to carry a composite
video signal. But then he goes on to call it audio, so perhaps not.

To the original poster: Video, whether composite or component, is
carried on 75 ohm cable. Digital audio (S/PDIF, Dolby Digital, or DTS)
is also carried on 75 ohm cable. So the coax that is used for any of
these purposes is interchangeable. You can buy a video cable and use it
for digital audio. You can buy a digital audio cable and use it for video.

However, analog audio does NOT require 75 ohm wire. So most typical
left/right stereo audio cables are NOT suitable for carrying video or
digital audio.

 

[Guest]

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"Jim Gilliland" wrote ...
> However, analog audio does NOT require 75 ohm wire.
> So most typical left/right stereo audio cables are NOT
> suitable for carrying video or digital audio.

I guess it depends on your definition of "suitable"?

For short distances (2-3 feet), barbed-wire is "suitable" in the
sense that it will work. Certainly such short distances do not
know or care whether you have an impedance-matched transmission
line or simply something that will get the ones and zeroes to the
other end intact.

 

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Sseadoubleyou wrote:

> Can you use a 'regular' left or right composite cable to make a coaxial
> connection or do you have to get an actual coaxial cable? I wasn't
> sure if the coaxial cable was wired or made differently inside then the
> audio composite cables were.

It would help answer you if you explained what you mean by a 'composite
cable'. It is not a term in standard use.

Coaxial simply means what it says. The signal and shield conductors share
the same axis. Simply a cable where the signal conductor runs inside a
circular shield made from braided or lapped wire.

Many types of wire use this construction. The term 'coaxial' is in practice
normally specifically used to denote suitability for radio frequency use (
including video and digital audio ).

Typical audio 'single screened' cable is not normally called coaxial
despite having that style of construction. Audio cable like this isn't
intended for radio frequewncy use either.

No cable is called composite, although coaxial cables are regularly used to
make 'composite video' connections ! Composite video refers to the type of
signal - not the cable.

Graham