Part 11: Cable and Interconnect Specifications

There's a lot of hype and just plain misinformation about cables and interconnects. Manufacturers sometimes feel the need to invent technical reasons for why their cables sound better than the competition's. In reality, cable design is largely a black art, with good designs emerging from trial and error (and careful listening). Although certain conductors, dielectrics, and geometries have specific sonic signatures, successful cable designs just can't be described in technical terms. This is why cables should never be chosen on the basis of technical descriptions and specifications.

Nonetheless, some cable and interconnect specifications should be considered in some circumstances. The three relevant specifications are resistance, inductance, and capacitance. (These terms are explained in detail in Appendix B.)

A cable or interconnect's resistance, more properly called DC series resistance, is a measure of how much it opposes the flow of current through it. The unit of resistance is the Ohm. The lower the number of ohms, the lower the cable or interconnect's resistance to current flow. In practice, cable resistance is measured in tenths of ohms. Resistance isn't usually a factor in interconnect performance (except in some of the new non-metallic types), but can affect some loudspeaker cables-particularly thin ones-because of their higher current-carrying requirements.

The sounds of interconnects and loudspeaker cables can be affected by inductance. It is generally thought that the lower the inductance, the better, particularly in loudspeaker cables. Some power amplifiers, however, need to see some inductance to keep them stable; many have an output inductor connected to the loudspeaker binding post (inside the chassis). When considering how much inductance the power amplifier sees, you must add the cable inductance to the loudspeaker's inductance.

Capacitance is an important characteristic of interconnects, particularly when long runs are used, or if the source component has a high output impedance. Interconnect capacitance is specified in picofarads (pF) per foot. What's important isn't the interconnect's intrinsic capacitance, but the total capacitance attached to the source component. For example, 5' of 500pF-per-foot interconnect has the same capacitance as 50' of 50pF-per-foot interconnect. High interconnect capacitance can cause treble rolloff and restricted dynamics. (A full technical discussion of interconnect capacitance is included in Appendix B.)

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