Inner Workings: Inside a High-End Audio Cable
If you've ever wondered whether it's worth it to splurge for premium audio and video cables, join the club. Given the Viagra-like claims of enhancement made by some manufacturers, it's often hard to separate the science from the fiction. But it's safe to say that a well-built, well-shielded, and well-insulated cable made with high-quality components will last longer, perform more reliably, and possibly reject interference better than a cheap one.
Slice open a high-quality cable and you'll see why better cables cost more. Take, for example, the SCA-D digital audio cable ($150 for a 2-meter length), part of Tributaries' top-of-the-line Silver Series of interconnects. Maybe the first thing you'll notice is the black nylon-mesh sleeve covering the blue PVC sleeve that serves as the cable's external insulation. The mesh helps protect the cable from abrasions and structural deterioration.
Beneath the PVC sleeve are three layers of metal sheathing: two layers of copper braiding plus an aluminum Mylar outer layer. In coaxial cables, the metal sheathing is actually a second conductor tasked with protecting the inside conductor from radio-frequency interference (RFI) and electromagnetic interference (EMI). The sheathing prevents noise from entering the signal path by shunting its energy to ground. In the SCA-D cable, the copper shielding handles frequencies below 50 megahertz (MHz), while the aluminum Mylar layer guards against interference above 50 MHz. Eschewing the point-to-point soldering used in cheaper cables, Tributaries uses what it calls "360° Surround Soldering," which completely envelops the connection between the shield and the conductor to create a more secure ground contact.
Beneath the braided shielding lies a white tube that runs the length of the cable - that's the dielectric material, in this case Teflon. Dielectrics are nonconductive materials that insulate the conductor from the shields. Air (or, really, a vacuum) is the perfect dielectric, but you can't use it in cables because the dielectric must keep the center conductor and outer shield from coming into contact. While many less expensive cables use PVC, Teflon has a lower capacitance (or a lower dielectric constant).
At the cable's heart is the central conductor, which in Tributaries' cables is made of oxygen-free, high-conductivity copper wire, with a 55-micron plating of pure silver. Having the molten copper wires cool and harden in an oxygen-free environment rather than in air makes them less brittle and subject to breaking. The thin silver plating is slightly less resistive than copper, and its surface oxidizes quickly and then prevents further oxidation, producing more consistent conductivity.
The construction of the connectors is also important, since the connector is where the rubber meets the road, electrically speaking. While most cables use two-piece RCA connectors formed by crimping the head to the strain-relief section (which can loosen over time), Silver Series interconnects use "full-body" connectors milled from a solid piece of brass and then plated with gold.
For more on audio/video cable construction and selection, see Basic Cable: Choosing the Right Cables for Your System