5
Limiter
The limiter switch located on the back panel of the amplifier enables the limiter. When the limiter
switch is in the off position, at full power output the amplifier will clip the peaks of the music sig-
nal and the clip LED will illuminate. The music could sound distorted. When the limiter switch is
in the on position the limiter acts more like a leveler. This allows the bass thumps in music to
drive the output of the amplifier into clipping for the duration of the thump, but will not heavily
clip a continuous signal like someone screaming into a microphone. This mode is useful for public
address applications where the full headroom of the amplifier is utilized and the quality of the
voice is maintained by using the soft clipping feature of the limiter.
Short Circuit Protection
The CR12 is fully protected against all possible passive loudspeaker load conditions. It can operate
with a “dead” short continuously without damage (we don’t recommend that you short your CR12
“just-for-fun”). Shorts create a lot of stress on the output devices. If a short is present on the output of
the amplifier with a signal passing through the amplifier then the protect LED will illuminate and the
amplifier will go into “sleep mode” turning off the audio signal passing through the amplifier. After
8 seconds, the amplifier will allow the signal to pass through the amplifier and check to see if the
short has been removed. If the short is still present the amplifier will go through the sleep mode cycle
again. If the short has been removed, the amplifier will continue to drive the speaker. The output
protection will allow the output of the amplifier to drive a loudspeaker with up to 35 degrees of
phase shift at 4-ohms.
Cooling & Thermal Protection
A two-speed fan cools the heatsinks of the amplifier. When the amplifier’s heatsinks are cool the
fan operates in low speed. When the amplifier is driving music into loudspeakers, and the
heatsinks temperature rises above 45 degrees Celsius, the fan switches to high speed. After the
heatsinks cool below 40 degrees Celsius the fan returns to low speed. When operating the CR12
care should be taken to allow cool air to enter the front of the amplifier and the hot air to exhaust
out of the rear. The CR12 was designed to run cool under normal operating conditions, but
restricting the airflow around or through the amplifier could cause the amplifier to thermally
shutdown.
If the temperature on the heatsinks in the CR12 exceeds the safe operation temperature, the
amplifier will shutdown illuminating both protection LED’s and turn off the audio signal to the
speaker output jacks until the heatsink temperature drops to a safe level.
Rack Mounting:
The CR12 was designed to mount into a standard 19-inch rack. Care must be taken to provide
adequate ventilation around the amplifier and the rack itself should have adequate ventilation to
the outside air. Leave the front and back of the rack as open as possible to allow the intake and
exhaust air to flow in and out of the amplifier.
Clip / Protection LED’s
The clip/protection LEDs on the front panel will blink to visibly indicate any signal excursion
beyond the dynamic headroom of the amplifier. The clip/protection LEDs will remain on when
the amplifier goes into its protection mode. The CR12 will go into protection for one of three rea-
sons:
• the power switch of the amplifier has just been turned on or off.
• The amplifier has a shorted speaker load on the output of the amplifier.
• The temperature on the heatsinks of the CR12 exceeds the safe operation temperature.
LIMITER
OFF
ON
