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In order to get sound in and out of your computer you need some
kind of A/D [Analog/Digital] and D/A [Digital/Analog] converters
(called ADC and DAC, respectively). Mac computers have small 1/8-inch
jacks built in that can serve this purpose. Some PC machines also
have similar connections that come stock. These converters are fine
for getting started, but they aren't optimized for serious recording
applications. They tend to sound thin and their audio connections
are of a low quality -- mini jacks aren't professional grade connectors.
In order to take the next step in fidelity, you need to invest in
a sound card designed to work with a digital audio sequencer
application.
There are a ton of sound cards on the market today, and the sheer
number of choices can be overwhelming. In order to discriminate
between all the different types, I break them into four categories:
basic I/O [in/out], multi I/O, multi I/O with MIDI, and laptop connections.
Basic audio interface cards are just that, basic. They are
PCI expansion cards with 1/4-inch balanced stereo ins and outs and
maybe a consumer grade digital connection like S/PDIF.
Multi I/O interfaces have multiple ins and outs and usually
support several digital formats, including AES/EBU (the professional-grade
digital connections). Connections may be directly on the faceplate
of the PCI card, or more commonly, an external breakout box is employed
to house the connections. The breakout box is usually connected
to the PCI card via a proprietary cable capable of carrying multiple
audio channels.
Some multi I/O interfaces also include MIDI ports. These
are convenient because a separate MIDI interface is not required
for MIDI connectivity.
Any audio interface that isn't based around a PCI card (or other
expansion card type like ISA) I'm calling a laptop interface.
These include USB and Type II PC Card slot connections, and FireWire
also qualifies. Of course, these interfaces could be used with a
desktop computer setup as well. I'm just calling them laptop interfaces
because they hook up so easily with laptop computers. Because laptops
don't have PCI slots, these connection types are really the only
options. USB interfaces are actually becoming increasingly popular
for desktop setups of all flavors. No opening your computer and
fiddling around trying to install a PCI card; just plug the USB
connector in and go. While Type II PC Cards will probably remain
exclusive to laptops, FireWire audio interfaces are poised to eventually
replace USB (especially for more professional applications). FireWire
is not subject to the bandwidth limitations of USB (for example,
most USB interfaces cannot record more than four simultaneous inputs).
Audio interfaces vary in quality in terms of bit depths, sampling
rates, converters, and connections. Consumer-grade sound cards and
the stock I/O found on Macs and certain PC computers are at the
bottom of the heap. Typical mini-jack connections and low quality
converters yield poor fidelity. Top of the line sound cards, in
conjunction with the right recording program, can achieve 32-bit,
96 kHz resolutions. The quality of converter used on the interface
is also very important, sometimes more so than the bit and sample
rate specs (if the converters don't sound good, the bit and sample
rates don't mean much.). High-end converters can exceed 110 dB signal-to-noise
ratio (S/N). Frequency response is also a factor, and most good
converters have specs that exceed the human hearing range (20 Hz
to about 20 kHz).
Audiomedia III - for Mac and PC: www.digidesign.com
CardDeluxe - for Windows 95/98 and Windows NT: www.digitalaudio.com
Mia by Echo Digital Audio - for Mac and PC: www.echoaudio.com
Delta44 by M-Audio - for Mac and PC: www.m-audio.net
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