|
Audio
Cables and Connections
by
Bill Fisher |
Testing
1, 2, 3:
Connect it right and get it clear.
Last
month we began a two-part series on connectivity
with a look at video cables. This month, we'll
look at audio cables and connectors, since choosing
the right audio connection can be just as important
as your video signal path. The discussion below
puts the choices in order from best to only so-so. |
FireWire
As
we discovered last month, FireWire is the gold
standard for high-quality desktop video connectivity.
Not surprisingly, it's also ideal for moving digital
audio from tape to your editing system and then
back again. Formally (and formerly) known as the
IEEE-1394 protocol and marketed by Sony and other
electronics companies as i.LINK, FireWire was
invented in the mid-1990s by Apple Computer.
How
It Works
- Carries
a bi-directional audio/video data stream with
time code and machine control between devices
that understand the IEEE-1394 protocol.
-
Provides a fully digital pathway; signal degradation
and other problems common to analog connections
aren't an issue.
- Better-than-CD
quality 16-bit, 48kHz stereo audio playback
from the camcorder.
How
It Connects
- Ports
are built into most digital camcorders and many
new computers; accessory cards are also available.
- Connectors
are four-pin or six-pin. The tiny u-shaped four-pin
connectors are found on camcorders; the larger
rectangular six-pin connectors are used at the
receiving end on computers and internal cards.
- Cables
are four-pin to four-pin, four-pin to six-pin,
or six-pin to six-pin. The first can connect
one camcorder to another for digital dubbing;
the second connects a camcorder to a computer
or hub; and the third connects two powered hub
devices.
How
to Use It
- Connect
a camcorder to a computer with a FireWire cable
and then power on the camera ("hot-plugging")
to activate the bi-directional DV stream.
- Playback
and print your project to tape from your editing
system with fully digital, lossless audio fidelity.
How
the Cable Measures Up
- Four-pin
connectors are extremely small and fragile,
leaving them vulnerable to early failure.
- Ultimately,
as a data protocol, quality is unlimited and
perfect and depends on system software and audio/video
applications to function.
|
XLR
XLR
cables and connectors are the top of the line
for making analog audio connections. Also known
as Cannon connectors, these devices provide a
balanced transmission between high-end audio devices,
like microphones and DAT decks, to ensure pristine
audio reproduction without electronic interference.
How
It Works
- Two-wire
balanced cables (the most common type of XLR
connection) feature a 3-pin connector linked
to a 2-wire twisted copper pair and a ground
lead.
- Each
of the wires in the twisted pair - the "high"
and the "low" - carries an audio signal
that's identical to the other, but 180-degrees
out of phase, providing a fail-safe that's known
as a balanced signal. This ensures you get maximum
signal fidelity.
- Available
on some consumer and many professional camcorders.
How
It Connects
- Three-pin
connector. Male connectors are used for audio
output and female connectors accept input.
- Spring-loaded
locking tab ensures a solid connection.
How
to Use It
- Connect
a quality microphone to a high-end audio deck.
- Connect
an audio or video deck with XLR outputs directly
to a PC interface card for digitizing and final
output.
How
the Cable Measures Up
- Extremely
durable metal connector and robust cable.
- Heavily
shielded to ensure interference is kept to a
minimum.
- Balanced
signal path allows long cable runs and high
signal fidelity.
- XLR
connectors available only on expensive pro-audio
and video devices and analog-to-digital interface
cards.
- Can
be tricky to adapt to other equipment.
|
RCA
RCA
cables and connectors are found on televisions,
VCRs, stereos and camcorders so they'll allow
you to connect almost anything to almost anything
else. Though not nearly as robust as XLR, RCA
connections clearly win in the convenience category.
How
It Works
- Cables
feature a single wire and a ground lead.
- Carries
analog audio signal in the form of a sine wave.
How
It Connects
- Pin-and-cuff
design - male cable ends plug into the female
device sockets.
- Look
for stereo connectors marked in white (left)
and red (right - although you can connect them
however you want) on the back panels of many
consumer devices, as well as on camcorders.
Some VCRs and camcorders feature mono audio
with a single connector.
- Many
of today's small camcorders have a small adaptor
cable that goes out from the camcorder and terminates
in three RCA connections: yellow for the video
and white and red for the audio.
How
to Use It
- Use
to monitor audio output from a camcorder or
nonlinear editing system; connect RCA jacks
to a powered speaker system, television or VCR.
- Connect
two decks or camcorders to make tape copies.
- Use
to pass analog audio from a FireWire device
to a VCR or television.
How
the Cable Measures Up
- Cables
vary widely in quality, length and best use.
- Heavier
shielding yields a cleaner signal.
|
| 1/4"
Phone (6.3mm)
 Though
less and less common in a world of FireWire and
USB, 1/4" phone connectors can still provide
a robust signal path for some audio devices. These
cables send a mono or stereo signal along a single
path, making them a fine connectivity choice when
other options aren't available.
How
It Works
Cables
use two or three conductors to transmit mono or
stereo signals.
Carries
audio as sine wave.
How
It Connects
- For
mono audio, male connector uses tip and sleeve
conductors and plugs into female socket; for
stereo, male end has tip, ring and sleeve conductors
to send left and right signals.
Most
frequently seen on powered speakers, microphone
and instrument cables, mixers and headphones.
How
to Use It
- Use
to connect a microphone or instrument to an
audio input device like a recorder or mixer.
-
Connect high-quality headphones to a headphone
jack.
How
the Cable Measures Up
-
Long runs can make cable vulnerable to high
levels of radio frequency and magnetic interference.
- Heavy
shielding and high-quality connectors are a
must.
|
1/8"
Mini (3.5mm)
Tiny
1/8" mini connectors have virtually replaced
the 1/4" connection in the world of consumer
audio. Though neither as robust nor as capable
as 1/4" cables, 1/8" mini connections
are an essential piece of any system that uses
consumer audio and video equipment.
How
It Works
- Two,
three or four conductors transmit mono or stereo
audio or stereo audio with video in the case
of the special 1/8" audio/video connector
used on many smaller camcorders.
-
Single wire carries audio as sine wave.
How
It Connects
- For
stereo audio, male connector has tip, ring and
sleeve conductors; special A/V connector has
tip, sleeve and two ring conductors for an added
video signal path.
- Find
these used for computer audio output, camcorder
headphone connections and camcorder analog audio
and video output.
How
to Use It
- Connect
audio output from a PC to powered speakers or
a VCR (adapter required - see below) to monitor
and record audio from a nonlinear system or
other application .
- Connect
a camcorder's analog audio/video outputs to
a VCR or television for monitoring and dubbing.
- Connect
headphones to a camcorder or PC for close listening
and preliminary audio mixing.
How
the Cable Measures Up
- Connectors,
especially female sockets, are extremely fragile
and notorious for failing; look for good construction
and be gentle.
- Cable
is thin and very lightly shielded; heavier construction
is best.
|
The
Long and Short of Cables
Shorter
cables are always better. Since all connecting
cables, including FireWire, are subject to some
degree of electrical and magnetic interference,
it's important to use the shortest cables you
can; the longer the cable, the more the signal
deteriorates and the more chances there are that
your audio will pick up interference.
USB
Audio Transfer
You
may have seen devices on the market that let you
capture analog audio via an interface box with
a USB connection to your computer. It's a great
idea, since USB is economical and even more common
than FireWire, but it's not for everyone. All
of these "breakout boxes" must perform
their own analog-to-digital conversion and some
devices are better at that than others.
Are
all cables made the same?
There
are wide variations between cables made by different
manufacturers and it's undeniable that some are
better than others. You'll often see an emphasis
placed on gold connectors; these can be helpful
in avoiding corrosion at the contacts, but we've
never seen a corroded cable in our living room.
With thinner-gauge (20-gauge is thinner than 12-gauge)
cables like RCA and 1/8" mini, heavier construction
can mean better sound and longer life-span. And
whatever the connector, look for plenty of shielding
- some manufacturers use almost none and it definitely
makes a difference.
The
Adaptor Puzzle
Many
of us have used adapters and adaptor cables to
get from one analog connector type to another.
Adaptors can be lifesavers: they can help make
the leap from, for example, the 1/8" stereo
mini audio out from your computer to the double
RCAs on your VCR. But they can also cause problems.
They add another potential source of interference
and signal loss to your system.
Line
vs. Microphone
Watch
out: there are a few different voltage levels
that might be used for analog audio connections.
The higher voltage line level outputs can damage
microphone level inputs, so make sure you check
the type of connection before you power up. For
example, camcorders typically have microphone
(level) inputs while mixers often output a line
level signal. |
