Digital Sound & Music: Concepts, Applications, & Science, Chapter 5, last updated 6/25/2013
live sound reinforcement is pictured in Figure 5.1. In this setup, a microphone an analog
device detects continuously changing air pressure, records this as analog voltage, and sends the
information down a wire to a digital mixing console. Although the mixing console is a digital
device, the first circuit within the console that the audio signal encounters is an analog
preamplifier. The preamplifier amplifies the voltage of the audio signal from the microphone
before passing it on to an analog-to-digital converter (ADC). The ADC performs a process
called digitization and then passes the signal into one of many digital audio streams in the
mixing console. The mixing console applies signal-specific processing such as equalization and
reverberation, and then it mixes and routes the signal together with other incoming signals to an
output connector. Usually this output is analog, so the signal passes through a digital-to-analog
converter (DAC) before being sent out. That signal might then be sent to a digital system
processor responsible for applying frequency, delay, and dynamics processing for the entire
sound system and distributing that signal to several outputs. The signal is similarly converted to
digital on the way into this processor via an ADC, and then back through a DAC to analog on the
way out. The analog signals are then sent to analog power amplifiers before they are sent to a
loudspeaker, which converts the audio signal back into a sound wave in the air.
Figure 5.1 Example of a simple live sound reinforcement system
A sound system like the one pictured can be a mix of analog and digital devices, and it is
not always safe to assume a particular piece of gear can, will, or should be one type or the other.
Even some power amplifiers nowadays have a digital signal stage that may require conversion
from an analog input signal. Of course, with the prevalence of digital equipment and
computerized systems, it is likely that an audio signal will exist digitally at some point in its
lifetime. In systems using multiple digital devices, there are also ways of interfacing two pieces
of equipment using digital signal connections that can maintain the audio in its digital form and
eliminate unnecessary analog-to-digital and digital-to-analog conversions. Specific types of
digital signal connections and related issues in connecting digital devices are discussed later in
this chapter.
The previous figure shows a live sound system setup. A typical setup of a computer-based
audio recording and editing system is pictured in Figure 5.2. While this workstation is
essentially digital, the DAW, like the live sound system, includes analog components such as
microphones and loudspeakers.
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