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How a cable lets outside sources of energy affect signal
As stated previously, second fundamental way of altering a signal passing through an audio cable is to introduce outside sources of energy. This outside energy is typically termed "noise". By definition, if any energy is absorbed by signal, signal has been distorted.
There are many potential sources of noise around audio cables. Some of more common sources of noise, such as radio frequency waves, are familiar to most people. When wiring up a radio, frequently a consumer must attach an antenna. Antennae are intentionally designed to channel radio frequency energy into a stereo. Just like an antenna, it is entirely possible for an audio cable to pick up radio frequency energy. If you are not intending to listen to radio, this is not a welcome effect. Electronic components, electrical cords, sound waves, and even sun, are all capable of creating noise. Electrical cords create electromagnetic fields around them that can transfer energy to a cable. Sound waves create mechanical vibrations that can be transformed into electrical energy that is added to an audio signal. Because there are so many different types of noise, there are many methods used to prevent a cable from picking up noise. Shielding, twisting of conductors, and mechanical damping are all common noise protection methods in cables.
While noise affects both interconnects and loudspeaker cables, generally effects are far more significant in interconnects. This is because signals in interconnects have far less energy. Since most forms of noise are inherently low energy to begin with, this means that it is far easier for them to modify low energy interconnect signals than high-energy loudspeaker cable signals.
Macro vs. Micro
The parameters discussed so far have been primarily "macro" effects. These are for most part top-level parameters that effect cables. These parameters as well as others not discussed here also exist at a "micro" level. Taking capacitance as an example, a given cable will have an overall capacitance that can be measured. This overall capacitance is a "macro" level parameter. The same cable can also be analyzed as 1000 separate but connected pieces. Each piece will have a local capacitance. These local parameters are "micro" effects and can have their own impact on signal separate from "macro" effects.
The impact that "micro" level parameters have on an audio signal is usually less than impact of "macro" level parameters. However, they do still make a difference in signal transfer. The various ways that audio companies choose to either mitigate or ignore these "micro" level details is, in part, responsible for vast array of different cable designs. From cryogenic treatments and precious metal wires, to fine silk insulation and fluid filled cable jackets; extreme cable designs abound. Will I hear difference?
The fact of matter is that cables do alter sound going through them, and that it is audible. You do not need to be an expert, or an audiophile, to hear difference. To demonstrate this point, simply listen to your stereo. If you close your eyes, does it sound like music is being played live right in front of you? This is what audiophiles strive for, and unless you have a very high-fidelity system, your answer to this question will most likely be no. You may have a hard time describing what exactly does not sound right about your system, but you know that it doesn't sound like a live performance.
Of course, reason why music does not sound live cannot be blamed solely on cables. The degradation of sound occurs in every component of your system. However, point here is that even a casual listener can detect subtle distortions that can prevent music playback from sounding live. Improving quality of your audio cables will improve sound quality of your system.
It is fairly safe to say that no matter what cable you use, modifications to sound will be small. Audio cables will never cause a listener to hear a piano when a flute is being played. However, it is small detail that makes all difference between good and bad quality sound. That is why very strong opinions are formed about various cables. As audio systems continue to improve in accuracy, listening to a "live" performance in your living room gets closer to reality. Cables are an enabling factor for advancements in audio reproduction and can play a remarkably important role in your system.
Written by: Adam Blake CEO / Co-Founder Pear Cable, Inc. www.pearcable.com For a more detailed explanation of cable design theory that Pear Cable thinks is relevant, see "cable design" white paper available on pearcable.com
Adam Blake is CEO and Co-Founder of Pear Cable, Inc., a manufacturer of high-fidelity audio cables. www.pearcable.com