Extron Electronics MLA VC10 Plus User Guide - Manual (Page 27)

Maximum voltage range limit
Some amplifiers use a maximum voltage that is lower than 10 VDC. Using a voltage that
exceeds the requirements of the amplifier can damage the equipment. Using a voltage
that is lower than the requirements of the amplifier will limit the maximum audio volume
reached. Determine what the maximum signal requirements are for the amplifier you are
using and use SIS commands to set the maximum control voltage that can be provided by
the MLA VC10 Plus.
ATTENTION: If you are controlling the volume using voltage, be sure that you know
the control voltage range for the amplifier that you are using. Consult
the user guide for the amplifier you are using or
measure it , following
the instructions starting on page 8. Setting the control voltage too
high for the amplifier may damage that equipment.
The MLA VC10 Plus can control amplifiers that use a maximum control voltage that is
greater than 10 VDC but the maximum volume for the amplifier may not be reached.
Maximum resistance range limit
Some amplifiers use a maximum resistance that is lower than 10 kilohms. Determine the
requirements for the amplifier and, if necessary,
set the values using SIS commands
(see page 35).
NOTE: All Extron amplifiers use the default 10 kilohms resistance control.
The resistance between the reference (V) and ground (G) pins of the MLA VC10 Plus is
always 10 kilohms. When a maximum range limit is applied to the resistance control, it
only limits the maximum resistance across the wiper (C) and ground (G) pins. This usually
limits the maximum volume output from the amplifier.
If using 3-pin potentiometer control to connect to an amplifier that requires a total
resistance of anything other than 10 kilohms, Extron still recommends that the 10 kilohms
setting be used to ensure full volume range.
Inverse Mode
By default, when the voltage is 0 VDC or the resistance is 0 ohm, the volume is considered
muted. At 10 VDC or the resistance is 10 kilohm, the volume is considered maximum.
Some amplifiers reverse their voltage or resistance requirements. Maximum volume is at
0 VDC or 0 ohm and the minimum volume (mute) at 10 VDC or 10 kilohm. For these
amplifiers, the volume control knob on the RS-232 control processor works counter-
intuitively: turning it clockwise decreases the volume and turning it counterclockwise
increases the volume.
Inverse mode reverses the resistance or voltage control signal sent to these amplifiers
so that the volume control knob on the RS-232 control processor works the way the
user expects: clockwise decreases the voltage or resistance, but increases the volume,
counterclockwise increases the voltage or resistance, but decreases the volume.
NOTE: Inverse mode should be disabled (the default setting) for all Extron amplifiers.
The inverse mode can be turned on or off (default), using SIS commands (see page 35).
MLA VC10 Plus • Operation 21