MM
™
-8802 User Manual
Page 32
http://aa.peavey.com copyright 2001 All Rights Reserved
External DC Power Supply Interface
CV Input Notes....
In most applications, the DC voltage would come directly from the MM-8802's CV ports. However, you can connect external
voltages to the MM-8802’s control ports as well. This is handy when using external controllers that output precise variations
of voltage for control. In this case, you would have to connect the MM-8802’s ground to the ground of the external voltage
source, and the positive DC voltage (0-10 V DC) from the external controller to the CV “IN” or return pin.
In addition to the previous examples, the CV input ports provide even more options for external control of software devices. In
fact, the functionality of these ports and their associated software devices is limited only by the imagination of the system
designer.
Besides the switch, rotary control, and external voltage options shown in this manual, other common configurations include
opto-isolators, resistive voltage dividing networks, and TTL logic inputs.
Try to keep in mind that the CV input port is essentially an analog “portal” to a 256-step software device that resides inside of
the MediaMatrix
®
system. The voltages that you return to the port represent values within the software, that are converted to
actual control actions. These values are based on how many control positions are required, and how they are divided among
the 256 steps, or increments of 10 volts. For example, in a switching configuration, there are only two values, ON or OFF.
When the return pin sees 10 volts, an ON condition is present. How fine the range between ON and OFF is a matter of calibra-
tion.
In the case of variable controls, such as a fader that has a value of -100 dB to 0 dB, the range of the control voltage is calibrated
across 256 individual values that represent the audio range of the control. Exactly how much voltage that is required for the
control to adjust to exactly -12 dB, again, is a matter of calibration within the software.
For fixed position routers, the equation is even simpler. Since the port is simply distributing voltages across a common control,
a single multiple-position audio router requires only one port to operate its select switches. If the router has four inputs, the
voltage required to switch the inputs is based on a four-part division of 10 Volts. For an 8-input device, the division is eight,
and so on. The MediaMatrix software provides functionality to calibrate the external control, so that you can compensate for
wire distance, voltage loss, etc.
The DC voltage required to operate the software side of the external control input port is based on a 10 Volt scale. The range of
effective control is 0-10 V, which is divided into 256 steps within the software. Therefore, you should use controllers designed
to output standard 0-10 V DC control voltages for optimal performance.
Ground
+ DC (0-10 V, Variable)
External Power Source
WARNING: Do not
exceed 10 volts DC
when using an external
power supply. Driving the IN pin
of the CV IN port with voltages
exceeding 10 V DC could damage
the MM-8802 and is not covered
under warranty!
