What audio cables are

Introduction

High-end audio cables are claimed to improve the sound quality of high-fidelity audio systems but whether they actually do is hotly disputed. Since the audio signal passes through cables on its way from the source to the amplifier, or from the amplifier to the speakers, the cables will affect that signal. Basic system frequency response can be calculated from the electrical properties of the cables, and components on either side of the cables. These electrical properties include resistance, capacitance, and inductance. For small-signal applications the degree of shielding are also important. All of these qualities are taken into account in the design of commercial and broadcast cables. High-end cables for the audiophile market often involve intricate construction geometries and exotic materials such as silver and oxygen-free, long-crystal, high-purity copper.

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Controversy

There is controversy among audiophiles surrounding the impact that high-end cables have on audio systems. The audibility of the changes is a matter of much debate. There are claims that, even among audiophiles, in a double-blind test it is difficult or impossible to distinguish extremely expensive, exotic speaker cables from ordinary lamp cords or budget 12AWG copper speaker wire.

James Randi, a stage magician and scientific skeptic best known as a challenger of paranormal claims and pseudoscience, offered a prize of one million dollars to anyone who could prove his or her ability to distinguish an expensive high-end audio cable from an ordinary audio cable by means of a controlled listening test. Michael Fremer of the Stereophile magazine took the challenge, but satisfactory testing conditions could not be agreed upon, and the test did not take place.

Blind and independent testing conducted by Lee Gomes of the Wall Street Journal demonstrated that 61% of 39 people tested at an audio show could differentiate between low end and high end speaker cables. Lee Gomes remarked, "That may not be much of a margin for two products with such drastically different prices, but I was struck by how the best-informed people at the show -- like John Atkinson and Michael Fremer of Stereophile Magazine -- easily picked the expensive cable". However, in more rigorous tests performed under controlled circumstances listeners have not been able to prove there is any audible difference between high end and cheap cables

Digital cables

One of the more contentious areas is in digital cable design, with high end cables being sold with claims of "distortion-free signal transfer." Some have argued that since the bit rates (approximately 1 Mbit/s) and distance traveled are considerably lower than for other data transfer technologies such as gigabit ethernet, any cable appropriately matched to the correct impedance requirement is sufficient. Others claim that jitter caused by imperfect impedance matching is very detrimental to the audio signal and the most substantial shortcoming of digital audio. This has led equipment manufacturers to design new standards such as I²S which separates clock and data signals or implement buffering and reclocking, although such standards are typically aimed at synchronising multiple signals to a single clock rather than attempting to correct errors due to jitter.

It is also worth noting that in independent testing, digital audio, at least of the S/PDIF sound format has been shown to be carried perfectly well over any length of wire of nearly any quality, including wire as simple as a coat hanger. Similar tests have not yet shown similar situation for analogue audio however.

Speaker cables

Another area of debate is speaker cables. Skeptics say that a few meters of cable from the power amplifier to the binding posts of the loudspeakers cannot possibly have much influence because of the complex crossover circuits found in most speakers and particularly speaker driver voice coils with several meters of wire.

A global concern with speaker cables is their inherent impedance relative to the impedance of the loudspeaker. Low impedance speakers are claimed to benefit most from low impedance cabling; this means thicker and/or shorter wires. It is claimed that longer cable runs need to be even thicker to minimize signal loss.

Main power cables

Another controversial area of audio cabling is that of mains power cables. Products exist that claim to improve the sound or picture with a short length of expensive oxygen-free copper or silver cable connected from the wall socket to the equipment. The several hundred of metres of standard grade cable in the walls and back to the sub-station seem to have been neglected in such claims. More scientific arguments have been presented, such as building RFI (Radio Frequency Interference) filters into the cables as well as shielding against EMI (Electro-Magnetic Interference) can produce a cleaner noise free supply and hence a better sound or picture quality. Although subjective tests have occasionally confirmed this, little objective proof has been given.