TOA a-503a Supplementary Manual
4
TOA Electronics Amplifier Guide
Chapter 2: Amplifier Basics
Important Concepts: Signal Flow, Level and Impedance
When designing and installing sound systems, mastery of some key concepts helps a great deal. A
basic understanding of signal flow, levels, and impedance can increase your efficiency on the job, and
dramatically reduce the number of costly call-backs.
basic understanding of signal flow, levels, and impedance can increase your efficiency on the job, and
dramatically reduce the number of costly call-backs.
Signal Flow: The Audio Chain
Signal Flow refers to the path of the sound from the source (page announcement, CD player, satellite
receiver, etc.) to the listener. This path can be very simple, using just a single source, a power amplifi-
er, and one or more speakers, or it can be complex, having multiple sources, multiple paths, and mul-
tiple destinations, with extra processing stages. A typical paging system signal path will begin with
two or three sources — for example, background music, paging audio from the phone system, and a
microphone (see fig. 1). These will be fed into a mixer, which combines the sources into one single line.
The mixer output may be fed into an equalizer, compressor or other processor, or directly to an ampli-
fier. The amplifier increases the power of the signal and feeds it to the speakers. In most smaller sys-
tems, the mixer and amplifier sections are integrated in one unit, which may include a built-in or
optional processing stage, such as an equalizing module for premium speakers.
receiver, etc.) to the listener. This path can be very simple, using just a single source, a power amplifi-
er, and one or more speakers, or it can be complex, having multiple sources, multiple paths, and mul-
tiple destinations, with extra processing stages. A typical paging system signal path will begin with
two or three sources — for example, background music, paging audio from the phone system, and a
microphone (see fig. 1). These will be fed into a mixer, which combines the sources into one single line.
The mixer output may be fed into an equalizer, compressor or other processor, or directly to an ampli-
fier. The amplifier increases the power of the signal and feeds it to the speakers. In most smaller sys-
tems, the mixer and amplifier sections are integrated in one unit, which may include a built-in or
optional processing stage, such as an equalizing module for premium speakers.
Σ
Mixer
Amplifier
PBX
Phone System
Microphone
Music Source
Processor
(optional)
Sources
Mixer/Amplifier
Speakers
Figure 1: Basic System for Paging and Background Music