In an audio system, interference may be directly audible or may enter amplifiers through feedback loops from either the input or output terminals. Ever since the development of high fidelity stereo technology a great deal of effort has been directed towards eliminating sound distortion due to imperfections in microphones, amplifiers and loudspeakers. The quest for superb quality sound has driven the market inducing it to improve every component of an acoustical system. It has long been known that the audio cables that supply the electrical signal and power from an amplifier to the speakers are critical components. It has become increasingly important that the signal is transmitted unimpaired between amplifiers and speakers and this has required special attention to the construction and routing of speaker cables. In particular, when the audio transmission cable constitutes a weak link in the chain, then the full advantage of the quality of the sound reproduction equipment and speakers is not being taken. Electrical cables and interconnects are important but frequently overlooked components of audio and video playback systems. Well-chosen cables and interconnects can help users get the best performance from their systems, whereas poor or incompatible cables result in poor performance. For example, if the electrical conductors that are used to form the audio cables are too small for the speakers and amplifier that are used, then power will be lost in the audio cables and the sound that will be reproduced by the speakers, in particular the lower frequency sounds, will be adversely affected.

High quality high-fidelity components used for music reproduction such as preamplifiers, amplifiers, digital-to-analog converters and tuners often employ analog signaling to convey the music signal from one component to the next. Signal degradation can occur in interconnects that convey signals between these components due to the interaction of the signal conductors with the driving and receiving components. A number of measurable interconnect parameters can contribute to this degradation including: inductance, capacitance, dielectric absorption, dielectric loss, bandwidth and susceptibility. For example in high fidelity audio systems, compact disc (CD) players are electrically connected to amplifiers and the outputs of those amplifiers are electrically connected to speakers and/or to headphones. In high fidelity systems, the analog electrical signals generated by the musical source or other audio source are degraded or distorted by the interconnecting cables that link the various components of the audio system together. When an electrical signal is transmitted over a cable from a transmitting end to a receiving end, frequency-dependent attenuation may cause the waveform of the signal at the receiving end of the cable to be significantly different from the waveform of the signal at the transmitting end. Besides interference from the outside, the weak signals traveling in interconnect cables may be affected by noise generated in the cable itself caused by interaction between wire strands, so called microphony, and by tribo-electric charges and discharges in the dielectric materials which separate the signal carriers from one another and their shielding.

Commercially available audio cable, used to interconnect audio components such as compact disc players, amplifiers and speakers, transmits different frequency signals within the audio frequency range at different velocities of propagation. The audio frequency range is generally considered to include frequencies from about 15 Hz to about 20 kHz while the radio frequency range is generally considered to extend upwardly from about 150 kHz. Radio frequency noise which is internally generated in audio equipment can be conducted into the signal cable, and can cause spurious oscillations and modal resonances in the cable. When audio signals are transmitted through a cable formed by a plurality of conductors the relatively high frequency components of the signal pass through the cable at a faster rate of speed than the relatively low frequency components. Thus the higher frequency components arrive at the end of the cable before the lower frequency components resulting in a signal at the end of the cable that is not a perfect replica of the signal introduced to the cable. The lower frequency components tend to move towards the higher magnetic field in the center of the cable, which further slows down the lower frequency components causing a further delay of the lower frequency components. Interfering radio frequency signals may audibly change the bias of amplifier stages and may result in indirect distortion of the output signal, and in some cases may cause overheating due to inaudible amplification of high frequency interference. When a cable of this type is connected between components in a music reproduction system the result is an aberration, in the form of smearing or smudging, of the reproduced music.

The most important sources of signal degradation arise from the interaction between the individual strands of multi-stranded conductors and a phenomenon known as the skin effect. Skin-effect can cause the music signal to become attenuated at some frequencies and distorted or smeared due to changing phase as the frequency changes. Skin effects are present due to the wide band of frequencies that are present in most high-fidelity music material. The currents associated with the low frequencies tend to travel deeper within the cross-section of the conductor than the high frequencies which tend to travel more on the outer surface skin of the conductor. In the skin effect, signals traveling at the "skin" or farthest radial distance from the center of a conductor induce time shifts in signals traveling near the center of the conductor. The skin effect is a factor at audio and higher frequencies: because the self-inductance of an electrical conductor is greatest at the center of the conductor, higher-frequency signals encounter a lower-impedance path towards the outside of the conductor, which reduces the effective cross-sectional area of the conductor at those frequencies, which in turn increases the impedance of the conductor at those frequencies. Skin effect is a challenging problem in that it is a common cause of distortion and adversely affects signal transmission.

In order to prevent degradation of analog signals during transmission from one component to another, balanced or differential signaling techniques are sometimes employed. Balanced signaling involves the transmission of two versions of the analog signal on each of two conductors. Audio cables are usually shielded in order to prevent a central conductor, conducting the audio signal, within the cable from picking up outside electrical signals, such as hum from power wiring and other interference. The circuitry within audio equipment (e.g., CD players, preamplifiers, amplifiers, tape players, etc.) is sometimes shielded by means of a grounded metal box to block outside electrical signals from interfering with the low level audio signals being generated within the audio equipment. Typically, the cross-sectional area of conductors used in a wire or cable is chosen in view of the expected magnitude of transmission current. The diameter of the conductors is also typically chosen to minimize the phenomenon known as skin effect, which is present when electrical current is transmitted through wire. In order to improve the noise to signal ratio, often balanced constructions are preferred over single ended cables. This is done either by replacing the single center conductor in a coaxial cable with a twisted pair or by arranging the second signal carrier as a braided tube concentrically surrounding the center carrier, the whole construction again surrounded by a braided, grounded shield. Various cables, including a metallic core and a surrounding sleeve of magnetically permeable material, have been developed for transmission of radio frequency signals to reduce radio frequency attenuation.

Since we have known that audio cables have to satisfy specific requirements and transmit the electrical signals in an optimal mode with minimal losses and distortions. This is especially important for acoustic instruments and apparatuses of high fidelity. There are currently five types of geometries utilized in high-fidelity single-ended and balanced cables, the coaxial, the twisted-pair, the parallel-pair, the woven and the helical-pair. Coaxial cables for use in a variety of purposes are well known since beginning of the last century. Main characteristics of the coaxial audio cable are parameters that determine the ability of the cable to transmit electrical signals without loss and distortion, e.g., from the electrical amplifier to a load. The disadvantage of the coaxial arrangement is that there is significant capacitive coupling between the entire surface of the inner conductor and the inside surface of the overall shield conductor. Most types of coaxial constructions tend to have poor phase linearity when used with consumer electronics. Speaker cables typically comprise a pair of insulated round conductors having terminals at their ends, which terminals are connected to audio components in a sound equipment system. In audio systems applications it is a well-known technique to twist the pairs of conductors carrying differential signals in interconnecting leads and in speaker cables to improve the noise rejection of the cables. Spurious RF signals which would degrade the sound quality are rejected by the twisted geometry. Standard audio cable transmits signals near the lower end of the audio frequency range. On the other hand, standard audio cable transmits high frequency audio signals.

In general, audio signal cables are required to support fine dynamics, separation, and rich overtones as well as presence and musicality. One important characteristic of the audio cable is impedance in all frequency ranges of the cable. Impedance is especially critical in the range of high and super-high frequencies. An optimum audio interconnect cable should achieve low capacitance and inductance, uniform low-loss dielectric (preferably air). Since audio cables are utilized to connect sources of audio analog electrical signals with the other audio components in an audio recording or playback system, for example, amplifiers, signal processors, mixers, tape recorders, A/D converters, CD players, etc. The cables used for them are usually different, because the kind of electric signal is different in amplitude and electric power according to the connection. Therefore, it is recommended to select cables for their compatibility with the other system components, and (in some cases) for their ability to enhance the overall sound or video output of the system. Similar considerations apply to cables used in high-end computer systems, servers, and other applications where distortion-free signal transmission is a priority.