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Composite vs. Component Cables
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? -- Posted via a free Usenet account from http://www.teranews.com |
Composite vs. Component Cables
From:
http://www.edmundoptics.com/techSupp...?articleid=297 Composite vs. Component Signal: Color video signals are composed of luminance and chroma information. Composite signals carry both luminance and chroma on one line, whereas Y-C and RGB signals carry luminance information on one line and chroma information separately on one or more lines. Breaking up the signal components generally improves signal fidelity, especially when recording or balancing color. -- RJ "Julian" wrote in message ... 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? |
Composite vs. Component Cables
"Julian" wrote in message ... 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? depends... the component threesome are all coax's, while the composite threesome may be 3 coax's or 1 coax (video) with 2 twisted pair (R/L). The former is fine, the latter would not be good. |
Composite vs. Component Cables
Oops, I did miss the point.
However -- and to pick nits, he wasn't "asking whether a cable labeled for composite use could be used for component signals," rather whether the composite three-cable bundle of audio/video, could be used as a substitute interface for a component video connection. -- RJ "Elmo P. Shagnasty" wrote in message ... You missed his point. He was talking about the physical cable, not the signal that's sent down it. He was asking whether a cable labeled for composite use could be used for component signals. - - - In article , 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? In article , "R. J. Salvi" responds: From: http://www.edmundoptics.com/techSupp...?articleid=297 Composite vs. Component Signal: Color video signals are composed of luminance and chroma information. Composite signals carry both luminance and chroma on one line, whereas Y-C and RGB signals carry luminance information on one line and chroma information separately on one or more lines. Breaking up the signal components generally improves signal fidelity, especially when recording or balancing color. |
Composite vs. Component Cables
On Sun, 5 Nov 2006 12:55:48 -0500, "R Sweeney"
wrote: "Julian" wrote in message ... 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? depends... the component threesome are all coax's, while the composite threesome may be 3 coax's or 1 coax (video) with 2 twisted pair (R/L). The former is fine, the latter would not be good. Also where the (red/white) audio cables are coax, these two are oftten thinner than the video (yellow) coax. That indicates that they probably have different properties with respect to impedance etc. Not good either. /Jan |
Composite vs. Component Cables
"Jan B" wrote in message Also where the (red/white) audio cables are coax, these two are oftten thinner than the video (yellow) coax. That indicates that they probably have different properties with respect to impedance etc. Not good either. /Jan correct, you need three matched impedence cables or else you are looking for trouble |
Composite vs. Component Cables
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. -- Want the ultimate in free OTA SD/HDTV Recorder? http://mythtv.org http://mysettopbox.tv/knoppmyth.html Usenet alt.video.ptv.mythtv My server http://wesnewell.no-ip.com/cpu.php HD Tivo S3 compared http://wesnewell.no-ip.com/mythtivo.htm |
Composite vs. Component Cables
"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. |
Composite vs. Component Cables
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. -- Grant Edwards grante Yow! TONY RANDALL! Is YOUR at life a PATIO of FUN?? visi.com |
Composite vs. Component Cables
R Sweeney wrote:
"Jan B" wrote in message Also where the (red/white) audio cables are coax, these two are oftten thinner than the video (yellow) coax. That indicates that they probably have different properties with respect to impedance etc. Not good either. /Jan correct, you need three matched impedence cables or else you are looking for trouble Not if you are only going two meters. 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 |
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 |
Composite vs. Component Cables
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. |
Composite vs. Component Cables
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 |
Composite vs. Component Cables
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? |
Composite vs. Component Cables
"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 |
Composite vs. Component Cables
"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. |
Composite vs. Component 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 |
Composite vs. Component Cables
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 |
Composite vs. Component Cables
"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 |
Composite vs. Component Cables
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. |
Composite vs. Component Cables
I haven't seen a published spec for RCA connectors since they are virtually
never used for anything but low frequency applications when their reactance is negligible. They are not appropriately used for RF applications. They can. however, be measured and thus characterized like any other physical object to specify how they behave. Just as their ohmic resistance can be measured with an ohmmeter, their reactance can be measured (as a function of frequency) to see if they are capacitive, inductive, or have negligible reactance. The results of these two measurements are combined (vector summed) to form the impedance. Like virtually any other connector, RCA connectors have insulators which separate the (center) terminal and ground, and this insulation has a dielectric constant which will be very different if the insulator is Teflon versus something cheap like Bakelite or cardboard. An ohmmeter will not see this difference, but a 2 GHz RF signal certainly will. RCA connectors, like many other types of connectors are not specified this way since they are not intended to be used this way, just as a Molex power connector is never characterized with this specification. The fact remains, however, (and this was my original and only point in replying to your erroneous statement) that an RCA connector (as well as a piece of wet spaghetti) has a characteristic impedance. The phrase simply means that it displays resistive and reactive components (which vary as a function of frequency) and these collectively characterize the device / object, just as explicitly as an Amphenol PL-259 RF connector does. Smarty "Matthew L. Martin" wrote in message ... 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 |
Composite vs. Component Cables
You really have some very confused concepts going on here. Take a cable
which is a small physical length relative to the signal it is attempting to pass. Put connectors on it which exhibit considerable reactance. Try to get the signal injected at the input to show up at the output. Let's, for example, use an RCA cable which has a few picofarads of capacitance due to its insulator being made of cheap plastic (as opposed to glass or Teflon) and put a high frequency signal into it. Let's try 5 GHz. The connector's shunt capacitance at this frequency makes it look like a dead short circuit. The cable length beyond the connector will be of little or no consequence, since the characteristic impedance of the RCA connector creates a huge impedance. The length of the subsequent cable is of little or no importance, but transmission line theory and Smith Charts would allow a very accurate prediction of the combined effect if both the RCA connector's characteristic impedance as well as the cable's characteristic impedance and attenuation factors are known. Smarty "Matthew L. Martin" wrote in message ... 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 |
Composite vs. Component Cables
Smarty wrote:
I haven't seen a published spec for RCA connectors since they are virtually never used for anything but low frequency applications when their reactance is negligible. They are not appropriately used for RF applications. If there is no spec, there is no characteristic impedance. No two RCA connectors need be anywhere near alike. The simple fact is that when RCA connectors are used, shielding is far more important than the characteristic impedance of the connection 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 |
Composite vs. Component Cables
Don't you understand? Characteristic impedance is a quantified / measured
value no different from voltage, length, or mass. An RCA connector has all 3, as well as many more characterizations. Everything ***can*** be characterized by measurement, and yet it doesn't always make sense to do so. Nobody, for example, is interested in the impedance of a sheet metal screw and therefore you seldom would see it measured or published. Similarly, the length or the mass of a resistor is seldom characterized since these are not the important specifications. RCA connectors have a characteristic impedance just as a wet piece of spaghetti has a characteristic impedance if you choose to measure it. Nobody cares, and thus the characteristic impedances for these 2 items are not typically measured or published. Thus, I can't show you are reference on the web or other citation, but I could certainly measure the characteristic impedance of either. The original and final point I have been making all along here is that your original reply to the post stating that RCA connectors do not have a characteristic impedance is false. They do, but it is not generally of interest since the connectors are used mostly at low frequencies where their impedance effects are negligible. At hi def frequencies, these effects cannot be ignored. Cable is a "distributed" impedance with its' reactance and resistance distributed linearly along its' length (unless the cable is damaged, crimped, or otherwise not lying undistorted in free space). An RCA (or any other) connector is a "lumped" impedance which can and will cause an impedance discontinuity if installed on a length of cable, regardless of its' length and regardless of the frequency of use. The severity of the impedance mismatch and the resulting reflections / attenuation / phase distortion / delays can only be correctly described by taking all of these effects into account. There are textbooks on transmission line theory which are devoted to these topics. You can oversimplify the process and state: The connector has no impedance" or "The 1/4 wavelength stub is too short" or some other such statement which reveals a lack of understanding of what is truly the physical phenomena. If you do, I will step in, as I did, and provide a correct explanation. Smarty "Matthew L. Martin" wrote in message ... Smarty wrote: I haven't seen a published spec for RCA connectors since they are virtually never used for anything but low frequency applications when their reactance is negligible. They are not appropriately used for RF applications. If there is no spec, there is no characteristic impedance. No two RCA connectors need be anywhere near alike. The simple fact is that when RCA connectors are used, shielding is far more important than the characteristic impedance of the connection 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 |
Composite vs. Component Cables
"R. J. Salvi" wrote in message ... Oops, I did miss the point. However -- and to pick nits, he wasn't "asking whether a cable labeled for composite use could be used for component signals," rather whether the composite three-cable bundle of audio/video, could be used as a substitute interface for a component video connection. Bzzt, picking the wrong nit there. He asked if the cables were physically the same, presumably so he could use his old composite cable in a component setup and save a few bucks. For a short run, it should be fine. -- RJ "Elmo P. Shagnasty" wrote in message ... You missed his point. He was talking about the physical cable, not the signal that's sent down it. He was asking whether a cable labeled for composite use could be used for component signals. - - - In article , 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? In article , "R. J. Salvi" responds: From: http://www.edmundoptics.com/techSupp...?articleid=297 Composite vs. Component Signal: Color video signals are composed of luminance and chroma information. Composite signals carry both luminance and chroma on one line, whereas Y-C and RGB signals carry luminance information on one line and chroma information separately on one or more lines. Breaking up the signal components generally improves signal fidelity, especially when recording or balancing color. |
Composite vs. Component Cables
In article , Jim Gilliland
wrote: 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. O.K. you guys. I now think I have the answer I was looking for. They are basically the same (in a physical sense) except that "component" cables are normally of a higher quality than "composite" cables, and therefore (normally) command a somewhat higher price for an equivalent length of cable. Thanks all. -- Posted via a free Usenet account from http://www.teranews.com |
Composite vs. Component Cables
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Composite vs. Component Cables
"JerrySmith'sTightEnd" wrote in message
t... "R. J. Salvi" wrote in message ... Oops, I did miss the point. However -- and to pick nits, he wasn't "asking whether a cable labeled for composite use could be used for component signals," rather whether the composite three-cable bundle of audio/video, could be used as a substitute interface for a component video connection. Bzzt, picking the wrong nit there. He asked if the cables were physically the same, presumably so he could use his old composite cable in a component setup and save a few bucks. For a short run, it should be fine. Please re-read my post...I admitted missing the original point, but for good reason. There's a fair amount of latitude exercised describing cable differences when the term "PHYSICAL" is used, as used by Julian (original poster). R, L &C, dialectric, terminations, gauge, shielding and design, etc. And judging by the diversity of responses to the original poster, I'd say there was a fair amount of interpretation on the subject in general. The fact that Julian used the term "bundle" when referring to composite cable(s), lead me to believe his understanding of the differences between composite and component was blurred. Hence, I copy/pasted a definition illustrating the signal differences between composite and component, presumably to illuminate their lack of interchangability (composite is comprised of one cable, component, three). Fwiw to Julian...I am using a Radio Shack 3-cable A/V composite video, stereo audio bundle (don't know the catalog number), as a component interface between my DVD player and DLP. Works great. -- RJ |
Composite vs. Component Cables
I think the main factor would be the capacitance between the center conductor an
the shield. No sure if that applies here, but the higher the frequency sent through the cable, the more its natural capacitance comes into play. -- All the Best Richard Harison "Smarty" wrote in message ... Don't you understand? Characteristic impedance is a quantified / measured value no different from voltage, length, or mass. An RCA connector has all 3, as well as many more characterizations. Everything ***can*** be characterized by measurement, and yet it doesn't always make sense to do so. Nobody, for example, is interested in the impedance of a sheet metal screw and therefore you seldom would see it measured or published. Similarly, the length or the mass of a resistor is seldom characterized since these are not the important specifications. RCA connectors have a characteristic impedance just as a wet piece of spaghetti has a characteristic impedance if you choose to measure it. Nobody cares, and thus the characteristic impedances for these 2 items are not typically measured or published. Thus, I can't show you are reference on the web or other citation, but I could certainly measure the characteristic impedance of either. The original and final point I have been making all along here is that your original reply to the post stating that RCA connectors do not have a characteristic impedance is false. They do, but it is not generally of interest since the connectors are used mostly at low frequencies where their impedance effects are negligible. At hi def frequencies, these effects cannot be ignored. Cable is a "distributed" impedance with its' reactance and resistance distributed linearly along its' length (unless the cable is damaged, crimped, or otherwise not lying undistorted in free space). An RCA (or any other) connector is a "lumped" impedance which can and will cause an impedance discontinuity if installed on a length of cable, regardless of its' length and regardless of the frequency of use. The severity of the impedance mismatch and the resulting reflections / attenuation / phase distortion / delays can only be correctly described by taking all of these effects into account. There are textbooks on transmission line theory which are devoted to these topics. You can oversimplify the process and state: The connector has no impedance" or "The 1/4 wavelength stub is too short" or some other such statement which reveals a lack of understanding of what is truly the physical phenomena. If you do, I will step in, as I did, and provide a correct explanation. Smarty "Matthew L. Martin" wrote in message ... Smarty wrote: I haven't seen a published spec for RCA connectors since they are virtually never used for anything but low frequency applications when their reactance is negligible. They are not appropriately used for RF applications. If there is no spec, there is no characteristic impedance. No two RCA connectors need be anywhere near alike. The simple fact is that when RCA connectors are used, shielding is far more important than the characteristic impedance of the connection 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 ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Composite vs. Component Cables
On Mon, 6 Nov 2006, Julian wrote:
O.K. you guys. I now think I have the answer I was looking for. They are basically the same (in a physical sense) except that "component" cables are normally of a higher quality than "composite" cables, and therefore (normally) command a somewhat higher price for an equivalent length of cable. As a first-level approximation, this is correct. Component cables will generally "work" if used as a composite cable. That does not mean that this is a preferred, or suitable, use. But, if the choice is between using a component cable or nothing, then use it. A good layman's metaphor is that using a composite cable as a component cable is like using junk food as food. Junk food will quell your hunger pangs, and it will deliver some amount of nutrition. Junk food is also certainly better than starvation. On the other hand, a diet of junk food is generally not good daily nutrition, nor is it good for you in the long term. This is different from the issue of "Monster" cables, which are generally ridiculously overpriced and quite unnecessary. A "Monster" cable is the equivalent of a $1000 restaurant meal; it may be "better" than an ordinary meal cooked at home, but the price/performance favors the home cooking. Home cooking also wins price/performance over junk food; junk food is convenient but not particularly cheap. It's all based upon what the cable is being asked to do. Delivery of an analog audio signal to a modest amplifier and speakers is not a particularly strenuous task for a cable; even the smallest and cheapest cables will do. Delivery of RF or video signals requires somewhat more from a cable; and inadequate cables will not perform as well. The impact ranges from the unnoticable to distortion or loss of performance. Case in point. When receiving satellite TV in a fringe area, a better cable between the dish and receiver will deliver a usable signal about 300 miles further out than an inferior cable. Or, under adverse weather conditions, a better cable will deliver a usable signal when an inferior cable will not. A component video cable delivers analog video, albeit in one color (and thus making HD possible). It's like RGB, only different. :-) If a composite cable is used, two of the lines will probably have a signal of inferior quality to the third. Depending upon your equipment you may, or may not, notice the difference. As long as you don't buy a "Monster" cable, a good-quality component video cable is relatively inexpensive compared to the rest of your system, and in my opinion it is false economy to use a composite cable as anything other than a temporary shim prior to the acquisition of a proper component cable. As a final aside, let's talk about digital cables (DVI or HDMI). With digital signals, either it works or it doesn't. If you have a $20 digital cable that works, you aren't going to get better performance by buying a $150 "Monster" cable. This is an excellent example where you can save your money. Similarly, it's obvious if a digital cable fails. Supposedly, the "Monster" cables are less likely to fail, but I have never had even an el cheapo digital cable fail barring physical abuse. Analog cables, such as component and composite cables, may have less catastropic failures that are less obvious as cable failure. I hope that this information is helpful. -- Mark -- http://panda.com/mrc Democracy is two wolves and a sheep deciding what to eat for lunch. Liberty is a well-armed sheep contesting the vote. |
Composite vs. Component Cables
I entirely agree. The shunt capacitance of the insulating dielectric at the
connector looks like a short circuit at high frequencies, and at lesser frequencies acts as a low pass filter. Smarty "Richard Harison" wrote in message ... I think the main factor would be the capacitance between the center conductor an the shield. No sure if that applies here, but the higher the frequency sent through the cable, the more its natural capacitance comes into play. -- All the Best Richard Harison "Smarty" wrote in message ... Don't you understand? Characteristic impedance is a quantified / measured value no different from voltage, length, or mass. An RCA connector has all 3, as well as many more characterizations. Everything ***can*** be characterized by measurement, and yet it doesn't always make sense to do so. Nobody, for example, is interested in the impedance of a sheet metal screw and therefore you seldom would see it measured or published. Similarly, the length or the mass of a resistor is seldom characterized since these are not the important specifications. RCA connectors have a characteristic impedance just as a wet piece of spaghetti has a characteristic impedance if you choose to measure it. Nobody cares, and thus the characteristic impedances for these 2 items are not typically measured or published. Thus, I can't show you are reference on the web or other citation, but I could certainly measure the characteristic impedance of either. The original and final point I have been making all along here is that your original reply to the post stating that RCA connectors do not have a characteristic impedance is false. They do, but it is not generally of interest since the connectors are used mostly at low frequencies where their impedance effects are negligible. At hi def frequencies, these effects cannot be ignored. Cable is a "distributed" impedance with its' reactance and resistance distributed linearly along its' length (unless the cable is damaged, crimped, or otherwise not lying undistorted in free space). An RCA (or any other) connector is a "lumped" impedance which can and will cause an impedance discontinuity if installed on a length of cable, regardless of its' length and regardless of the frequency of use. The severity of the impedance mismatch and the resulting reflections / attenuation / phase distortion / delays can only be correctly described by taking all of these effects into account. There are textbooks on transmission line theory which are devoted to these topics. You can oversimplify the process and state: The connector has no impedance" or "The 1/4 wavelength stub is too short" or some other such statement which reveals a lack of understanding of what is truly the physical phenomena. If you do, I will step in, as I did, and provide a correct explanation. Smarty "Matthew L. Martin" wrote in message ... Smarty wrote: I haven't seen a published spec for RCA connectors since they are virtually never used for anything but low frequency applications when their reactance is negligible. They are not appropriately used for RF applications. If there is no spec, there is no characteristic impedance. No two RCA connectors need be anywhere near alike. The simple fact is that when RCA connectors are used, shielding is far more important than the characteristic impedance of the connection 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 ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Composite vs. Component Cables
Smarty wrote:
Don't you understand? Characteristic impedance is a quantified / measured value no different from voltage, length, or mass. An RCA connector has all 3, as well as many more characterizations. Then tell us what the characteristic impedance of an RCA connector is. If you can't, stop typing nonsense. Is it not true that when RCA connectors are used, the shielding is more important than the impedance of the interconnect? 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 |
Composite vs. Component Cables
While it is indeed true that cables carrying digital signals (such as DVI)
most often either "work" or "don't work", the signals they are passing are, in their spectral content, the same as analog signals, and, in fact, have rise times and fall times which make their pulse edges exactly look like a (non infinite) series of analog waveforms rather than a true (idealized) pulsed waveform. Degradation to the digital waveform in a cable is not simply absent or present. In the same manner as analog transmission in a cable, the line and the connector act dispersively, add differential phase delays, differential amplitude attenuations, and phase / time distortions which can, and ***will** distort the waveform. The signal recovered at the end of the wire is indeed different from what is sent, and, for long lines, or poorly matched cables / connectors / driver electronics distorted to the point where it can become unusable. To the extent that manufacturers have chosen adequate wire and connectors for a given length, signal strength, etc......this problem is not normally visible to the consumer. Thus, most cables appear to either work or not work. Again, at the risk of seeming academic, the laws of physics still apply, and cables can and will truly degrade digital signals, in some cases to the point where they are unusable or badly distorted. Smarty "Mark Crispin" wrote in message nda.com... On Mon, 6 Nov 2006, Julian wrote: O.K. you guys. I now think I have the answer I was looking for. They are basically the same (in a physical sense) except that "component" cables are normally of a higher quality than "composite" cables, and therefore (normally) command a somewhat higher price for an equivalent length of cable. As a first-level approximation, this is correct. Component cables will generally "work" if used as a composite cable. That does not mean that this is a preferred, or suitable, use. But, if the choice is between using a component cable or nothing, then use it. A good layman's metaphor is that using a composite cable as a component cable is like using junk food as food. Junk food will quell your hunger pangs, and it will deliver some amount of nutrition. Junk food is also certainly better than starvation. On the other hand, a diet of junk food is generally not good daily nutrition, nor is it good for you in the long term. This is different from the issue of "Monster" cables, which are generally ridiculously overpriced and quite unnecessary. A "Monster" cable is the equivalent of a $1000 restaurant meal; it may be "better" than an ordinary meal cooked at home, but the price/performance favors the home cooking. Home cooking also wins price/performance over junk food; junk food is convenient but not particularly cheap. It's all based upon what the cable is being asked to do. Delivery of an analog audio signal to a modest amplifier and speakers is not a particularly strenuous task for a cable; even the smallest and cheapest cables will do. Delivery of RF or video signals requires somewhat more from a cable; and inadequate cables will not perform as well. The impact ranges from the unnoticable to distortion or loss of performance. Case in point. When receiving satellite TV in a fringe area, a better cable between the dish and receiver will deliver a usable signal about 300 miles further out than an inferior cable. Or, under adverse weather conditions, a better cable will deliver a usable signal when an inferior cable will not. A component video cable delivers analog video, albeit in one color (and thus making HD possible). It's like RGB, only different. :-) If a composite cable is used, two of the lines will probably have a signal of inferior quality to the third. Depending upon your equipment you may, or may not, notice the difference. As long as you don't buy a "Monster" cable, a good-quality component video cable is relatively inexpensive compared to the rest of your system, and in my opinion it is false economy to use a composite cable as anything other than a temporary shim prior to the acquisition of a proper component cable. As a final aside, let's talk about digital cables (DVI or HDMI). With digital signals, either it works or it doesn't. If you have a $20 digital cable that works, you aren't going to get better performance by buying a $150 "Monster" cable. This is an excellent example where you can save your money. Similarly, it's obvious if a digital cable fails. Supposedly, the "Monster" cables are less likely to fail, but I have never had even an el cheapo digital cable fail barring physical abuse. Analog cables, such as component and composite cables, may have less catastropic failures that are less obvious as cable failure. I hope that this information is helpful. -- Mark -- http://panda.com/mrc Democracy is two wolves and a sheep deciding what to eat for lunch. Liberty is a well-armed sheep contesting the vote. |
Composite vs. Component Cables
Matt,
This is not nonsense. This is basic electrical engineering. The impedance of an RCA connector, if I had to take an educated guess, would be 10s of megohms resistive and no less than 10K ohms reactive (capacitive) at the frequencies we are discussing. It is entirely clear that you will have not even a clue as to what this means. Smarty "Matthew L. Martin" wrote in message ... Smarty wrote: Don't you understand? Characteristic impedance is a quantified / measured value no different from voltage, length, or mass. An RCA connector has all 3, as well as many more characterizations. Then tell us what the characteristic impedance of an RCA connector is. If you can't, stop typing nonsense. Is it not true that when RCA connectors are used, the shielding is more important than the impedance of the interconnect? 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 |
Composite vs. Component Cables
Matt,
Shielding in the cable itself becomes important if the cable sits in a noisy environment, in which case the shield (which is nominally grounded) serves to prevent noise. Moreover, in multiconductor cables like component, RGB, etc......the shield reduces "cross-talk", the tendency of the emitted electromagnetic field arising from one conductor (let's say green, for example) to corrupt the neighboring signals (for red and/or blue). The connector's impedance becomes an issue if it begins to either attenuate (differentially) the signal such that higher frequencies become more attenuated than lower frequencies, or, if the impedance of the line itself is in the same range or higher than the connector impedance. To use a crude plumbing analogy.......a 1 inch pipe with low impedance to water flow would be severely impacted by connecting it through 1/4 inch connectors which present a large impedance to the water flow. Neither effect is necessarily more or less important. It requires an understanding of the physical phenomena and how they relate. The simple (and sometimes incorrect) answer is that RCA connectors for component video will most often suffice. And this is true despite their characteristic impedance................ Smarty "Matthew L. Martin" wrote in message ... Smarty wrote: Don't you understand? Characteristic impedance is a quantified / measured value no different from voltage, length, or mass. An RCA connector has all 3, as well as many more characterizations. Then tell us what the characteristic impedance of an RCA connector is. If you can't, stop typing nonsense. Is it not true that when RCA connectors are used, the shielding is more important than the impedance of the interconnect? 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 |
Composite vs. Component Cables
Smarty wrote:
Matt, This is not nonsense. This is basic electrical engineering. The impedance of an RCA connector, if I had to take an educated guess, would be 10s of megohms resistive and no less than 10K ohms reactive (capacitive) at the frequencies we are discussing. It is entirely clear that you will have not even a clue as to what this means. Look, if there is no specification for the impedance of an RCA connector, as there are for many cable ends when characteristic impedance is important, then it isn't important. Why can't you admit this? 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 |
Composite vs. Component Cables
"Jim Gilliland" wrote in message 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. I am looking at an AV cable that came with an old VCR that I keep on the computer to copy family tapes to DVD... the audio lines have 24 AWG printed on them. This is NOT a coax designation, but the description of a twisted pair. |
Composite vs. Component Cables
Matthew,
You ask me to "admit" that characteristic impedance is not important for this specific connector and I can only say that this is true if the connector is used in the manner for which it was originally intended, namely, audio and low bandwidth composite video. If it is used inappropriately for other applications, such as hi def TV, it very well may be extremely important. It was not my original contention that it was or wasn't important however. It was, and still is my only contention that this connector ***HAS A CHARACTERISTIC IMPEDANCE". This is a measurable, finite, and physically determined parameter / characteristic, just as a pipe connector has very specific characteristics. Saying (as you originally did incorrectly) that an RCA connector "has no characteristic impedance" is the same as saying it has no length, no width, no mass, etc. My comment was intended to correct that error, and requires no "admission" on my part of anything. Smarty "Matthew L. Martin" wrote in message ... Smarty wrote: Matt, This is not nonsense. This is basic electrical engineering. The impedance of an RCA connector, if I had to take an educated guess, would be 10s of megohms resistive and no less than 10K ohms reactive (capacitive) at the frequencies we are discussing. It is entirely clear that you will have not even a clue as to what this means. Look, if there is no specification for the impedance of an RCA connector, as there are for many cable ends when characteristic impedance is important, then it isn't important. Why can't you admit this? 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 |
Composite vs. Component Cables
R Sweeney wrote:
"Jim Gilliland" wrote in message 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. I am looking at an AV cable that came with an old VCR that I keep on the computer to copy family tapes to DVD... the audio lines have 24 AWG printed on them. This is NOT a coax designation, but the description of a twisted pair. Not necessarily. The center connector of a piece of coax can be labeled that way as well, especially if the coax isn't designed to meet any particular standard. Then again, it may be twisted pair in the case of your specific cable. It's not impossible to transfer audio over twisted pair, it's just not a particularly good idea. But I'm sure there are a few manufacturers that have cut that corner. In any event, I sure wouldn't try to use those wires (the audio ones) for any form of video. |
Composite vs. Component Cables
Julian wrote:
In article , Jim Gilliland wrote: 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. O.K. you guys. I now think I have the answer I was looking for. They are basically the same (in a physical sense) except that "component" cables are normally of a higher quality than "composite" cables, and therefore (normally) command a somewhat higher price for an equivalent length of cable. If that's what you took from my post, then you've missed the point entirely. As I said, the answer is NO, they are not equivalent. They are NOT the same in a physical sense. The difference is NOT just one of quality. They are distinctly different cables, and even though they may look the same, they behave differently. They are not interchangeable. In some circumstances, you may find that you can adequately pass video through a short length of audio cable. That doesn't make it the right cable for the job, and it's very likely causing some degree of degradation. As another poster pointed out, some manufacturers may use video cable to carry audio. In that case, the audio cables will work fine for video (for obvious reason). But without some sophisticated test equipment, you really have no way of verifying that. So even in this case, you can't safely make that assumption. |
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