Chapter 21: Audio/Visual Devices^541
The components included on the sound card to convert sound into and out of digital
data formats are as follows:
Digital to analog converter (DAC) The DAC converts digital audio data from
a hard drive or another storage medium into analog sound (normal everyday
sound waves) that can be played back on the speakers or a set of headphones.
Analog to digital converter (ADC) An ADC converts analog sound waves,
such as a voice or a musical instrument, into digital data so it can be stored,
edited, and transmitted. A little later in the chapter, I’ll go into why this
device and the preceding device are necessary when you work with sound
recording and playback on the PC.
Analog inputs Sound cards have two separate analog sound inputs: line-
level and microphone-level (a.k.a. mic-level). Line-level inputs accept sound
signals from electronic sources such as CD players or tape decks or signals
that are directly input from a musical instrument, such as an electronic piano
or a synthesizer. There are two separate inputs because microphones produce
signals with a much lower voltage level than those from line-level sources.
Mic-level inputs are generated from a stand-alone microphone or an unamplified
electric guitar plugged into the mic-level input. Line-level inputs are designed
to handle the higher voltage signal produced by amplified electronic devices.Figure 21-1. The AOpen AW744 Pro sound card. Photo courtesy of AOpen America, Inc.