Part 10: Terminated Cables and Interconnects

Some cables and interconnects are not merely pieces of wire, but contain electronic components. These cables are identified by "boxes" on one or both cable ends housing the resistors, inductors, and capacitors that form an electrical "network." Pioneered by Music Interface Technologies (MIT), these products are often called terminated cables (Fig.11-7).

According to MIT, some of the audio signal's voltage is stored in the cable's capacitance, and some of the signal's current is stored in the cable's inductance. The amount of energy stored in the cable varies with frequency, which is manifested as tonal and dynamic emphases at those frequencies. Moreover, the energy stored in the cable is released over time, rather than being delivered to the loudspeaker along with the rest of the signal. This frequency-dependent, non-linear energy storage distorts the size and shape of the soundstage, according to MIT.

Terminated cables are designed to prevent such energy storage, and to deliver all the signal to the loudspeaker with the correct phase (timing) relationship. MIT claims that terminated cables are essential to realizing correct bass weight, smooth tonal balance, and a full-sized soundstage with precise image focus.

Because terminated cables form a low-pass filter (i.e., they don't start filtering until about 1MHz, well above the audioband), they are useful for connecting very-wide-bandwidth electronics. The Spectral brand of electronics, for example, has bandwidths as high as 3MHz-not because the designer wants to pass those frequencies, but to make the circuits behave better in the audioband. Terminated cables filter those very high frequencies, ensuring that loudspeakers are never fed energy in the megahertz range, and making the system more stable.

<<back    next>>