ALC2 User’s Manual. Rev. 01
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7. Operation_____________________________________________________
Power On/Off switch
This control switches the mains AC power of the amplifier.
Gain controls
Two gain controls adjust level for their respective channels. The controls are calibrated in dB’s gain for the entire amplifier. In bridged mono mode, the channel 1
control controls the signal level. Remember, that in bridged mono mode the voltage gain of the amplifier is multiplied by two, so you must add 6 dB to the control
scale.
Indicators
Each channel of the ALC2 is equipped with five LED indicators:
Power:
These blue LEDs will illuminate when the amplifier is switched on.
Signal:
These yellow LEDs will illuminate when an input level of more than -40 dBu is present at the input of that channel. The signal LEDs work
independently of the setting of the input gain controls.
Clip:
The red clip LEDs will illuminate when the output of that channel has reached its maximum output voltage. The indication works for both positive and
negative peaks of the signal and is correct for every connected impedance. When the signal is distorted more than 0.5% due to clipping, the clip
limiter quickly reduces the gain to minimize the amount of overdrive. When a clip LED is flashing, it is recommended to decrease the signal level to
the
amplifier.
Protect:
The red protect LEDs indicate a number of conditions. 1. RF on the input. When a large amount of RF is detected on the input signal, the related
channel is muted. Removing the signal will automatically reset this condition. 2. DC on the output. When DC is detected on the output, the output
relay will open to protect the loudspeakers from DC. Usually this indicates a defect in the amplifier and the need for servicing. 3. High temperature.
When it is flashing, the output section of the related channel is between 85 and 90 degrees centigrade (185 - 194° F),and the ALC2 has shut down
its class-G stage. The amplifier will continue working, but at lower power. When it is constantly illuminated the temperature is above 90 degrees
centigrade (194° F), and the input of that channel is muted until the temperature has dropped to a safe value. When the amplifier is in thermal
protect mode, the fan is running at full speed. The protect LEDs will also illuminate during power-up of the amplifier to indicate power-up muting of
the
amps.
SDP Limit:
When you have installed SDP protection modules, these yellow LEDs indicate power- or excursion-protection limiting of the modules. Flashing of
these LEDs is normal, however the action of the SDP limiters can become audible if the amount of overdrive is too much.
