Specifications

CHAPTER 2
NOTE
One of the most common questions I get from readers is, “what sound card
should I buy?” There are so many different sound cards on the market,
providing so many different features, that I can’t simply recommend one or
the other. I can, however, tell you what features to look for so that you can
make an educated choice.
I’ve already mentioned that you should look for a PCI-based, DirectX-
compatible sound card. You should also be aware of the types of connections
that sound cards supply. The typical sound card provides a number of
different audio inputs and outputs including line level, microphone level,
and speaker. Line level inputs and outputs are used to transfer sound from
cassette decks, radios, electronic keyboards, or any other standard audio
device. Microphones generate a very small audio level by themselves, so they
need a special input of their own, which is connected to an internal
preamplifier on the sound card. Speakers also need their own special
connector with a built-in amplifier in order to produce a decent amount of
volume. Some high-end sound cards also offer digital inputs and outputs.
These special connectors let you attach the sound card directly to compatible
devices such as some CD players and DAT (digital audio tape) decks. Using
these connections gives you the best possible sound, because audio signals
stay in the digital domain and don’t need to be converted into analog signals.
You should also be aware that connectors come in a variety of forms. Low-
cost cards usually provide the same 1/8-inch jacks used for headphones on
boom boxes. For better quality, there are 1/4-inch, RCA, or XLR jacks.
Connections can also be balanced or unbalanced. Balanced connections
provide shielding to protect the audio signal against RFI (radio frequency
interference). Unbalanced connections don’t provide any type of protection.
If you want to be able to record more than one audio track at once, you’ll
need a card with multiple audio connections. Most average sound cards
internally mix all of their audio sources down to one stereo signal, but other,
higher-end (more expensive) cards let you record each device separately on
its own discreet stereo channel. This capability is much more desirable in a
music recording studio, but not everyone needs it. You’ll also want to look for
a card with full-duplex capabilities. This means the card can record and play
back audio simultaneously. This is opposed to a half-duplex card, which can
perform only one function at a time.
A good quality audio signal is something that everybody desires. During
recording, the sampling rate (which I talked about in Chapter 1) plays a big
part in the quality of the audio signal. Suffice it to say, the higher the
sampling rate that a sound card can handle, the better the sound quality. The
sampling rate of a CD is 44.1 kHz (44,100 samples per second) and all sound
cards on the market support this. Professional cards can hit 48 kHz or higher.
Bit resolution (which I also talked about in Chapter 1) is a factor in
determining digital sound quality as well. The more bits you have to
represent your signal, the better it will sound. The CD standard is 16 bits,
which is supported by all sound cards. Some cards (again, mostly high-end)
go up to 20, 22, or even 24 bits.
http://www.muskalipman.com
Getting Started with SONAR — Chapter 2
29