Hardware Reference
In-Depth Information
(2.0/2.1) configuration, you need to add a header cable to the motherboard.. If the mother-
board did not ship with the header cable, contact the vendor.
Volume Control
Withvirtuallyallrecentsoundcards,thevolumeiscontrolledthroughaWindowsControl
Panel speaker icon that can also be found in the system tray (near the onscreen clock). If
you're switching from a bare-bones stereo sound card to a more sophisticated one featur-
ing Dolby Digital or analog 5.1, 6.1, or 7.1 output or input, you need to use the mixing
options in the volume control to select the proper sources and appropriate volume levels
for incoming and outgoing audio connected to the card or a breakout box. Keep in mind
that if you are sending sound to an external audio receiver, you need to adjust the volume
on that device as well. Don't forget to enable digital output via the Sound Properties play-
back dialog if you are using the SPDIF output jack.
If the PC speakers are amplified but you aren't hearing sound, remember to check that the
power is on, the volume control on the speakers is turned up, and the correct speakers are
selected and properly connected.
MIDI Support Features
At one time, when evaluating audio adapters, you had to decide whether to buy a mono-
phonic or stereophonic card. Today, all audio adapters are stereophonic and can play mu-
sic using the MIDI standard, which plays scores using either synthesized instruments or
digital samples stored on the audio adapter or in random access memory (RAM).
Stereophonic cards produce many voices concurrently and from two sources. A voice is a
single sound produced by the adapter. A string quartet uses four voices, one for each in-
strument. On the other hand, a polyphonic instrument, such as a piano, requires one voice
for each note of a chord. Thus, fully reproducing the capabilities of a pianist requires 10
voices—one for each finger. The more voices an audio adapter is capable of producing,
the better the sound fidelity.
Early audio adapters used FM synthesis for MIDI support; the Yamaha OPL2 (YM3812)
featured 11 voices, whereas the OPL3 (YMF262) featured 20 voices and stereophonic
sound. However, virtually all audio adapters today use recorded samples for MIDI sup-
port; audio adapters using this feature are referred to as
wavetable adapters
.
Wavetable audio adapters use digital recordings of real instruments and sound effects in-
stead of imitations generated by an FM chip. When you hear a trumpet in a MIDI score
playedonawavetablesoundcard,youhearthesoundofanactualtrumpet,notasynthetic
imitation of a trumpet. The first cards featuring wavetable support stored 1MB of sound
clips embedded in ROM chips on the card or on an optional daughtercard. However, with
