onhometheater.com's Guide to
Audio Connections
Last time out, we tackled a
really confusing mare's nest of connections -- all those video terminators that have
proliferated in the last few years. Fortunately, the situation is a lot less complex on
the audio side.
Essentially, it all comes down to analog and digital.
If I had to reduce the choices to a simple rule of thumb, it would be choose digital
whenever possible. But, of course, it's not quite that easy. But before I plunge into
the digital realm, I'll quickly cover analog.
The analog audio connection most people are familiar with
is the RCA connection, which consists of a central signal-carrying pin surrounded
by a circular ground. To connect an RCA plug, you simply push the central pin into the
corresponding socket on the chassis of the component you're connecting.
If you're connecting a stereo component, there will
be two RCA jacks, typically labeled red for the right channel, white for the left (yellow
generally designates a composite-video connection). Multichannel systems frequently have
five or seven channels, and that's where the color-code system breaks down -- you'll need
to read the labels and be careful.
Another analog audio connection, sometimes used on high-end
A/V components, is called the XLR, or balanced audio connection. A balanced
connection uses a special type of connector called an XLR. Unlike RCAs, which are the same
on both ends of the cable, XLR connectors come in both male and female orientations. While
an RCA-terminated cable has two conductors, balanced connections have three,
carrying the positive, negative, and ground signals -- separating the ground and the
negative leg of the signal improves the signal/noise ratio.
One thing that makes digital so much easier than analog --
at least when it comes to hooking everything up -- is the fact that it doesn't matter how
many channels you're dealing with, everything is carried in a single cable. That part's
simple. However, there are several types of digital connection.
The most common these days is called TosLink, which
is an optical connection. That means that the signal is carried through a
fiber-optic cable as a series of pulses of light, as opposed to down a conductive wire
cable as a series of electrical pulses. There are some advantages to this -- there’s
less chance of electrical interference, for one -- but there are also disadvantages. For
example, optical connections are not good at transmitting signals over long distances.
Almost as common are coaxial connections. These look
like conventional analog RCA connections, but because they're digital, a single coaxial
connection can carry two, five, or even seven channels of audio.
There is also a digital connection called AES/EBU,
which uses XLRs. Like balanced audio connection, AES/EBU connectors are typically found
only on high-end components.
FireWire, or IEEE1394, is seldom used as an audio-only
connection. FireWire typically carries audio and video signals, and is increasingly found
on set-top boxes and components designed for whole-house integration. In theory, FireWire
will make all of the other connectors obsolete; only time will tell.
That's not quite everything you need to know about audio
connections -- we still need to cover speaker connections. I'll do that in the next
installment.
...Wes Phillips
wes@onhometheater.com
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