Why is a silver-plated, copper center conductor better than a copper center conductor? Is it even better?

Why is a silver-plated, copper center conductor better than a copper center conductor? Is it even better? Those are both good questions. Let's examine the differences and see if one conductor is better or worse than the other.

The center conductor is the main means of transmitting a video signal. The center conductor may come in various diameters, normally ranging from 14 gauge to 22 gauge. The makeup of the center conductor is generally solid copper or copper- clad steel, specified as bare copper weld, or BCW for short. For CCTV applications, solid copper conductors are needed. Copper clad, copper weld, or bare copper weld cables should never be used for CCTV, as they have a much greater loop resistance at baseband video frequencies. To determine which type of conductor it is, look at the center conductor, on the cut end. Cable that is copper-clad will be silver in the center, instead of solid copper all the way through the conductor. The amount of DC resistance offered by the cable is due to an overall effect of the size variation in the center conductor. A cable which contains a large diameter center conductor will have a lower resistance than a cable with a small diameter. The decreased resistance of a large diameter cable supports the ability of the cable to carry a video signal over longer distance with better clarity, but is also harder to work with and may be prohibitively expensive.

A characteristic of silver-plated copper conductors is great Hi-Fidelity dynamics. The upside to a silver-plated copper conductor is that it can make a system that sounds dull come to life. The down side to this type of conductor is that it loses quality in the areas of bass quality or LF delivery. Silver plated copper cables have also shown fatiguing over extended listening periods. Silver plated copper, or cables employing any two materials of different resistance properties, are best avoided for audio interconnects and speaker cables.

Silver has a lower resistivity than copper does. In other words, silver has less resistance to a signal than copper does. Because of this fact, a signal will travel farther along silver than the signal will travel along copper.

Frequencies like high Definition usually travel closer to the surface. Because silver has a gain of 10% in conductance, the transfer of data is better with silver plated copper center conductors than it is with copper center conductors.

The quality of the copper that comprises the copper center also has an effect on the performance of the cable. There are several different types of copper. Tough Pitch Copper, also called TPC, is unprocessed copper. This type of copper is usually used in general purpose cables, such as those used for power leads and numerous cheap audio cables. Tough Pitch copper is melted once and then the melted copper is formed into a wire, or cylindrical conductor, which is then cooled. After the copper conductor has cooled, the wire is drawn repeatedly to reduce the diameter to the desired size.

Around 1975, oxygen free copper, also called OFC, was developed because it had become more and more apparent that the quality of sound was related to the quality of the copper and the processing used during the manufacturing of the cable. This copper quality is manufactured through extrusion in an oxygen-free-inert-gas environment. This copper has less oxygen and other impurities, which makes it a better copper for sound transmission.

In the same year a method was developed by Hitachi to reduce the grain or crystal boundaries. This patented process is called LC-OFC and is the exclusive product of Hitachi. After the copper wire is extruded, the wire is heated again, or annealed, which further reduces grain and crystal boundaries.

Professor Ohno developed a patented method for a copper wire that was grain free using the extrusion process. When a pure metal becomes solid from a liquid, the crystals of the metal grow in a specific geometrical pattern, specific to that metal, that emanates from a nucleus, rather like a tree's dendritic growth pattern. The size of the crystals grown in the metal can be varied by repeatedly heating and cooling metal, like what is done in the LC-OFC process. The structure of a strand of copper may be compared to the structure of a bag of sugar. Every grain of sugar inside the bag has a crystal boundary. In a conductor, these crystal boundaries, which are potential barriers, act as a non-linear resistance to electrical current flow. Therefore the fewer boundaries there are, the less resistance there is to the electrical signal as it passes from one end of the conductor to the other.

This is why a silver-plated copper center conductor is better than a copper center conductor. The added silver-plating has less resistance than copper would in the same place. By adding the copper the resistance to electrical signals is actually lowered, ensuring better transmission of the electrical signals.