Making the connection

Wiring or cabling is an important component in any home theatre system, as without the right cable your amplifier won't be able to receive digital audio properly from the player and so won't be able to supply your surround speakers with the right audio signals. Read on to learn more...

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By  Jason Saundalkar Published  July 18, 2007

A home theatre system consists of a number of different components; a source, such as a DVD player or PC, an amplifier, and lastly the speakers. For the system to function properly each of these components must be able to talk to each other properly, therefore the cabling between them is very important indeed.

The cabling between the source and amplifier is of paramount importance because without the right cable the source won't be able to send its digital audio content, regardless of the standard it is recorded in (Dolby Digital etc), properly. In which case the amplifier won't be able to distribute audio to your surround speakers properly. The most commonly used cables today are optical and digital coaxial. To be on the safe side, make sure your surround amplifier can work with both optical and digital coax because certain sources may use one or the other.

Optical cable

Optical cables are the most interesting cable type because they carry data - in this case digital audio - in the form of pulses of light. These cables initially offered transmission rates of 3.1Mbits/sec, though they are now capable of 125Mbits/sec. They allow a source to send digital audio signals, encoded to any of the present audio standards, across to an amplifier, where the sound can then be distributed to the speakers.

Optical cables offer a number of advantages over standard electrical cables. From a physical perspective, the cables are thinner because shielding is not needed (as the light pulses are not susceptible to external interference). The transmission distance is also greater because unlike electrical signals, which degrade over long distances and even with shielding can be distorted by exterior interference, light pulses travel unaffected.

There are a number of downsides however, starting with price. You can expect to pay a 50% premium for an optical cable compared to the same length of digital coaxial. Moreover, optical cables can be easily damaged and, if severely bent, will not function at all, as light pulses can't easily navigate corners.

Digital coaxial

Digital coaxial cables function by sending data electrically through a copper wire sitting at the heart of the cable. The connectors used by these cables looks identical to that of standard RCA cables though that's where the similarities end.

In terms of downsides, coax cables are generally thicker than standard RCA cables and even optical cables because they are heavily shielded. Shielding is necessary on this type of cable because the signal can be affected by external interference and if the interference is severe enough, the transmission can fail altogether. These cables can't be very long either because even if they are shielded, the signal quality will deteriorate over long distances. Depending on the surroundings, interference can become a problem even on cables no longer than four feet.

The upside is that coaxial cables don't cost as much as optical cables and are quite sturdy as well. A coaxial cable is also unaffected by even severe bends.

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