A Discussion On Video Cable Construction
The question comes up repeatedly about the price of cables making a difference or not. Why spend big bucks for no apparent gain? Many people do not find any difference in the PQ of expensive cables and the lower priced brands and so forth.
So I thought a thread that focused on the engineering look at the construction of cables and the reasons behind the differences would be in order.
The bulk of the information required to get a pretty complete technical knowledge of the details is located here: Component Video Cables - The Definitive Guide and it is one of the best series of articles I have seen on the subject. However it is very technical and difficult for many laymen to comprehend.
Here are some excerpts of the paragraphs that are very technical in the article I pulled out that hits the main points of the paragraph:
|1.0 ENGINEERING 75-OHM INTERCONNECTS
Unlike audio cables, which only conduct low frequency data on the order of 20Hz to 20,000Hz, video cable must transmit higher frequencies up to levels of around 8MHz to 10MHz for NTSC and for over 35MHz for HDTV.
2.0 SIGNAL LOSS
2.1 Internal Impedance of 75-ohms
However, if audio cables are used in place of component video cables, or poorly constructed component video cables are used that are not a true 75-ohm characteristic impedance, the lower impedance value of these cables may result in a partial signal reflection do to a mismatch in impedance, depending on the length of the cable.
2.2 Electromagnetic Interference (EMI)
It is possible for stray signals from EMI to find their way into a video cable and therefore, create a false signal or internal noise
2.3 Mismatched Impedance
Since the source is a 75-ohm impedance, this reflected signal is sent directly back to it creating a delay effect at certain frequencies. This delay, for example, can show up as a ghost in the picture. Multiple ghosts resulting from multiple frequency reflections can look like ringing around the original image. These reflections can also cause partial signal cancellations at various frequencies corresponding to a partial signal loss resulting in a loss of picture detail or color.
2.4 Skin Effect
2.4 Flawed Cable Designs or Manufacturing Techniques
Both cables were hand soldered during manufacturing, yet it is clear that the cable on the left did not alter the diameter of the white colored dielectric while the cable on the right did. Also, look at the quality of the solder joint in the left side cable. There are no solder bulges, dielectric melting, or exposed wires. The result is the creation of as near perfect a 75-ohm termination as possible. The cable on the right is another story. It seems that little care was taken to protect the dielectric as seen by the noticeable melting near the end of the green jacket layer. Also, there are exposed conductor wires, no termination protection and the solder joint displays extremely poor quality. With inconsistencies and the multiple diameter changes of the conductor/dielectric on the right, it is obvious this manufacturer created a poor termination and this cable will likely have significant signal loss at certain video frequencies.
Pursuing the Truth: Don’t be afraid to remove the RCA barrel and inspect these solder joints for yourself. The connector barrel usually unscrews and can be slid down the cable without damage. Some manufacturers hard mount the RCA barrels by placing shrink sleeve over them or implementing other methods so they cannot be removed. These manufacturers may be so bold as to express elaborate reasons for doing this, but the bottom line is that if you cannot inspect their solder joints, you should use caution when selecting their cables.
This website has many other articles on cables, see: Cable Info Center
The remainder of the series is pretty easy to follow and I would recommend you read it if you are interested in information about cables.
A very good alternative to pre-made component cables that is used by many installers that pre-wire homes for home theater applications is RG6 quad coax cables. This cable is considered overkill for many, but considering the cost and the ruggedness of the cables, it is some of the best cables to use. We use a standard F connector attached to a F to RCA adapter to plug into the equipment. Many people do not like the RG6 because of the stiffness of the cables, but once it is routed neatly, it is fine.
Probably the most reconized brand of cables is Monster. If you want Monster cables they can be ordered from amazon.com here: Monster composite cables.