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FIG. 2: From left to right, common audio-cable connectors include RCA (consumer and semipro unbalanced line cables), male and female XLR (microphone and balanced line cables), and -inch TS (unbalanced line and instrument cables).

Audio cables typically use copper wire as a conductor because copper is inexpensive, pliable, and a good electrical conductor. However, copper oxidizes when exposed to air, forming copper oxide. This material is a poor conductor, which can cause a cheaply made cable or connection to degrade in performance over time.

Cables typically have hardware connectors fastened to the ends (see Fig. 2). Mic cables normally use XLR connectors, while line cables generally use ¼-inch or RCA connectors. Speaker cables often terminate in bare wires, but they can also use banana plugs or spade lugs. Cables with high-quality connectors, including those made from superior materials, are always a good investment. Gold is a good choice for cable connectors not only because it is an excellent conductor, but also because it is soft and will deform slightly to fill in all the gaps within a socket and create the best possible connection.

Size Matters
The diameter of a wire is an important consideration in cable design because it affects the wire’s ability to transmit audio effectively. The American Wire Gauge (AWG) protocol defines wire diameter on a scale where larger numbers indicate smaller diameters. For audio wire, typical gauges range from 4 AWG to 30 AWG. (See the table “Wire Gauge Diameters” for a list of wire gauges and their diameters.)

Here are some rules of thumb for estimating wire gauges. Solid-wire diameters change by:
a factor of 2 for every 6 gauges;
a factor of 3 for every 10 gauges;
a factor of 5 for every 14 gauges.

From this information and the “Wire Gauge Diameters” table, we can deduce that 18-gauge wire is approximately 40.2 thousandths of an inch (40.2 mils) in diameter, 12-gauge wire is 80.4 mils, and 6-gauge is 160.8 mils.

A wire’s cross-sectional area can also be estimated with another simple rule of thumb: when you change the gauge by 3 AWG, the cross-sectional area changes by a factor of two. For example, 17-gauge wire has twice the cross-sectional area of 20-gauge wire. This means that a 2-wire strand of a given gauge is the equivalent of a single wire three gauges lower.

This is an important concept in cable geometry, which refers to the physical configuration of the wire or wires used to make the cable. For example, some cables use a single, solid wire as a conductor. However, this is uncommon for audio cable, because a solid wire would make the cable stiff and difficult to work with. Most audio cable uses stranded conductors in which many thin wires are woven together to form a single conductor. This way, the conductor can offer the benefits of a large cross-sectional area but with greater cable flexibility.


Reprinted with permission from Magazine, January, 2001
2001, Intertec Publishing, A Primedia Company All Rights Reserved

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