User manual

3-2 P1200A User Manual
IMPORTANT!
Standard controls on
C4-SUB controller
module
C4-SUB
GRISP
MUTE
OVL
-12 dB
-6
+6
0
Clipping limiter
To maintain sound quality output stage clipping is kept within
reasonable bounds by a limiter circuit. The limiter threshold alters
to take account of the supply voltage to the mainframe power
amplifiers. So if the mains supply voltage or the connected load
impedance alter, then the limiter automatically tracks these changes
to maintain the system sound quality.
3.2. Controls and indicators
This section describes the controls & indicators common to all
P1200A controller modules. Loudspeaker specific controls and
indicators are explained in the sections dealing with the respective
loudspeakers.
OVL - Overload (red)
− Illuminates when an overload occurs in the signal path (input
signal too high)
− Illuminates when the amplifier gain is reduced because the
output current is too high (e.g. due to a short circuit).
ISP - Input Signal Present (green)
− Illuminates when the controller input signal exceeds -36 dBu.
The ISP circuit is unaffected by the setting of the controller mute
switch and level control.
GR - Gain Reduction (yellow)
− Illuminates when the controller limiters reduces gain by
more than 3 dB.
MUTE (red)
This switch mutes the system output without having to alter any of
the system level settings. The mute circuit acts by electronically
disconnecting the mainframe power amplifier output. The red LED
next to the MUTE switch illuminates to verify that the switch has
been selected.
If cabinets used in an array are muted, the movement of the
loudspeaker cones in those cabinets is no longer damped by the
influence of the mainframe power amplifier output. The removal of
damping to some drivers in an array makes them susceptible to
excitation by the other loudspeakers in the array. Audible
resonances may occur, and even absorption of low frequency
sound energy as the undamped loudspeakers act like a ‘bass trap’.
To permanently mute single cabinets of an array it is therefore
preferable to turn down or disconnect the input signal of the
corresponding controllers instead of using the MUTE switch.
When the mainframe is connected to the d&b remote control
system (d&b RIB and PC) it is possible to use the minimum input
gain setting (–57.5 dB) instead of the MUTE function.
Level control
The detented level control adjusts the controller input sensitivity
and has a 20 dB range, -14 dB to +6 dB, calibrated in 1dB steps.
The level control is normally set to 0 dB.