Composite vs. Component Cables

Grant Edwards wrote:
On 2006-11-05, Wes Newell wrote:
On Sun, 05 Nov 2006 11:38:44 -0500, Julian wrote:

I had a discussion with a techie friend of mind, who claimed that there
was no PHYSICAL difference between a "composite" cable bundle and a
"component" bundle of three cables (i.e. the only difference being the
kind of signal that is sent down the wires). They are physically
interchangeable.

Is this correct?
I wasn't going to reply to this, but since no one wants to give you a
simple answer, it's yes. The only difference other than wire size is the
color of the connectors. Each consist of 3 shielded rca cables.

Except that the impedance of the cable makes a difference. You
can't just use anything with RCA connectors on the ends and
expect good results with high-bandwidth signals.


RCA connectors don't have a characteristic impedance. If you are using
them, then you are more interested in shielding than impedance.

Matthew

--
Thermodynamics and/or Golf for dummies: There is a game
You can't win
You can't break even
You can't get out of the game

Julian wrote:
I had a discussion with a techie friend of mind, who claimed that there
was no PHYSICAL difference between a "composite" cable bundle and a
"component" bundle of three cables (i.e. the only difference being the
kind of signal that is sent down the wires). They are physically
interchangeable.

Is this correct?

Yes, they are physically interchangeable. The color coding will be off,
but that is easy enough to keep straight.

That said, the component signals carry higher frequencies on all three
cables, and the composite signals only carry audio signals on the red
and white cables. Low quality composite cables therefor might degrade
the component signals.

Try them and see.

Every connector has a characteristic impedance. It's basic physics. As you
may be aware, an impedance in nothing more a resistive component
(vectorially)combined with a reactive component. The resistive component is
not frequency dependent whereas the reactive (capacitive or inductive)
component is. At the frequencies of interest for hi def component signals
(over 100 MHz being typical) impedance mismatches can and do occur in
component connections as a result of cable, connector, and driver circuitry.
You are correct in stating that the type of cable and its' characteristic
impedance does make a difference, but the connector is not electrically
transparent nor is it necessarily impedance matched.

The reactive and resistive values of a typical RCA connector are nominally
very small at the maximum frequencies carrying hi def signals. This is why
their characteristic impedance is often conveniently ignored. Try squirting
2 GHz signals through them and they will behave very badly.

Smarty


"Matthew L. Martin" wrote in message
...
Grant Edwards wrote:
On 2006-11-05, Wes Newell wrote:
On Sun, 05 Nov 2006 11:38:44 -0500, Julian wrote:

I had a discussion with a techie friend of mind, who claimed that there
was no PHYSICAL difference between a "composite" cable bundle and a
"component" bundle of three cables (i.e. the only difference being the
kind of signal that is sent down the wires). They are physically
interchangeable.

Is this correct?
I wasn't going to reply to this, but since no one wants to give you a
simple answer, it's yes. The only difference other than wire size is the
color of the connectors. Each consist of 3 shielded rca cables.

Except that the impedance of the cable makes a difference. You
can't just use anything with RCA connectors on the ends and
expect good results with high-bandwidth signals.


RCA connectors don't have a characteristic impedance. If you are using
them, then you are more interested in shielding than impedance.

Matthew

--
Thermodynamics and/or Golf for dummies: There is a game
You can't win
You can't break even
You can't get out of the game

On 2006-11-05, Matthew L. Martin wrote:
On 2006-11-05, Wes Newell wrote:

I had a discussion with a techie friend of mind, who claimed that there
was no PHYSICAL difference between a "composite" cable bundle and a
"component" bundle of three cables (i.e. the only difference being the
kind of signal that is sent down the wires). They are physically
interchangeable.

Is this correct?
I wasn't going to reply to this, but since no one wants to give you a
simple answer, it's yes. The only difference other than wire size is the
color of the connectors. Each consist of 3 shielded rca cables.

Except that the impedance of the cable makes a difference. You
can't just use anything with RCA connectors on the ends and
expect good results with high-bandwidth signals.


RCA connectors don't have a characteristic impedance. If you are using
them, then you are more interested in shielding than impedance.

Where did I say anything about the RCA connectors having a
characteristic impedance??

--
Grant Edwards grante Yow! I wonder if I ought
at to tell them about my
visi.com PREVIOUS LIFE as a COMPLETE
STRANGER?

"R Sweeney" wrote in message
...

"Wes Newell" wrote in message
news:[email protected]
On Sun, 05 Nov 2006 11:38:44 -0500, Julian wrote:

I had a discussion with a techie friend of mind, who claimed that there
was no PHYSICAL difference between a "composite" cable bundle and a
"component" bundle of three cables (i.e. the only difference being the
kind of signal that is sent down the wires). They are physically
interchangeable.

Is this correct?

I wasn't going to reply to this, but since no one wants to give you a
simple answer, it's yes. The only difference other than wire size is the
color of the connectors. Each consist of 3 shielded rca cables.

not always...
I have video/stereo wire sets where the audio cables were twisted pair and
NOT coax.

Kimber...?

--
RJ

"Matthew L. Martin" wrote in message

correct, you need three matched impedence cables or else you are looking
for trouble

Not if you are only going two meters.

probably correct.

but why worry... triple coax cables are available that are as cheap as AV
cables.

Smarty wrote:
Every connector has a characteristic impedance. It's basic physics. As you
may be aware, an impedance in nothing more a resistive component

Please cite the impedance specification for an RCA connector.

Matthew

--
Thermodynamics and/or Golf for dummies: There is a game
You can't win
You can't break even
You can't get out of the game

Grant Edwards wrote:
On 2006-11-05, Matthew L. Martin wrote:
On 2006-11-05, Wes Newell wrote:
I had a discussion with a techie friend of mind, who claimed that there
was no PHYSICAL difference between a "composite" cable bundle and a
"component" bundle of three cables (i.e. the only difference being the
kind of signal that is sent down the wires). They are physically
interchangeable.

Is this correct?
I wasn't going to reply to this, but since no one wants to give you a
simple answer, it's yes. The only difference other than wire size is the
color of the connectors. Each consist of 3 shielded rca cables.
Except that the impedance of the cable makes a difference. You
can't just use anything with RCA connectors on the ends and
expect good results with high-bandwidth signals.

RCA connectors don't have a characteristic impedance. If you are using
them, then you are more interested in shielding than impedance.

Where did I say anything about the RCA connectors having a
characteristic impedance??


Since they don't have a specified characteristic impedance, the impact
of an impedance mismatch is expected to be negligible, especially when
the 1/4 wave of the carrier is much longer than the cable length.

Matthew

--
Thermodynamics and/or Golf for dummies: There is a game
You can't win
You can't break even
You can't get out of the game

"R. J. Salvi" wrote in message

not always...
I have video/stereo wire sets where the audio cables were twisted pair
and NOT coax.

Kimber...?

--
RJ

cheapies included with old VCR's mostly

Julian wrote:
I had a discussion with a techie friend of mind, who claimed that there
was no PHYSICAL difference between a "composite" cable bundle and a
"component" bundle of three cables (i.e. the only difference being the
kind of signal that is sent down the wires). They are physically
interchangeable.

Is this correct?


The basic answer is NO, they are not equivalent. Component video requires three
75 ohm cables. Composite video requires only one. There is no requirement for
the two audio cables in a composite bundle to be 75 ohm cables, so you have to
assume that they are not.

I'm not sure why we're seeing all the discussion about RCA connectors. The
connectors aren't the issue. The characteristic impedance of the coax itself is
what matters.

I'm also not sure why we're seeing any discussion of twisted pair. The audio
cables in a composite bundle are coaxial cables. They're just not the right
coaxial cables for video.