Signal Flow
Page 11
Peavey Electronics Corporation
Signal Flow
Signal flow is the basis for all audio system design. You cannot design and implement integrated audio systems without under-
standing the basics of signal flow, and how audio is transported between components. It is essential to all aspects of installa-
tion and maintenance. With the MM
™
-8802, it is equally important. You should understand the various stages of signal flow
within the MediaMatrix
®
system to accurately and efficiently configure, adjust, control and maintain the system.
As with all MediaMatrix systems, audio is separated into several fundamental processes. First, there is analog audio, real-world
waveforms that are a part of our everyday lives. This is what we hear and speak. Then there is digital audio. Code that repre-
sents “samples” of actual analog audio signals. This we cannot hear. And there is the conversion process. Audio must be con-
verted from analog waveforms to digital code and then converted again, back to analog for use in our acoustic world. Look
carefully at the illustration below.
In the above example, stereo audio from the CD player gets into and out of the MediaMatrix system via the MM-8802. First,
your CD player’s output is connected to the MM-8802’s input. The signal then passes the MM-8802’s analog gain stage and
gets converted to digital audio via the analog to digital converter (A/D). When the signal is past, or “after” the A/D converter, it
is in the digital domain. After the converter, it exits the MM-8802 via the TX side of the CAT 5 digital interface cable and
enters the MediaMatrix DSP. The two audio channels, left and right from the CD player are then “inside” the MediaMatrix dig-
ital processing engine or DPU. You use “wire” and audio “devices” to create any signal flow you desire for your CD audio signal.
You can split it, process it, mix it, switch it, squash it, loop it, delay it...whatever you need to do, you can do with MediaMatrix.
In this example, we have a stereo mixer, stereo compressor and stereo parametric EQ. The signal exits the DPU at the BoB out-
put block. After the signal is processed, it exits the MediaMatrix system and returns to the MM-8802 via the RX side of the
CAT 5 interface cable. It then hits another conversion stage, this time a digital to analog converter (D/A) where the digital sig-
nal data is returned to analog waveforms. It then goes through a final analog gain stage then shows up at the output terminal of
the MM-8802. It is this terminal that gets connected to the next component in your audio system, most often, the power
amplifier. (NOTE: When using the 9-pin legacy cable for interfacing the MM-8802, the TX and RX circuits are contained
within a single cable.) Notice that the MM-8802 has several software control panels attached to it. There is the master control
panel that includes all of the analog audio and external control interface functionality for the MM-8802. There are also control
panels attached to the input and output block within the MediaMatrix DPU. Understanding these control panels is vital to
good MediaMatrix implementation.
Analog to Digital
Converter
“Inside” the MediaMatrix.
Digital audio domain.
The DSP
MM-8802 Break-out-Box
Analog
Gain Stage
Analog Control
Digital Control
Digital to Analog
Converter
Analog
Gain Stage
External
Control Ports
Output
Drive Level
Input
Sensitivity
Analog audio components
TX
INPUT
OUTPUT
RX
