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4. OPERATION AND USAGE
4.1. Start up
Pushing the POWER (10) button lights up the integrated pilot light and both red CLIP
PROT (2, 8) LEDs during the approximately 10 seconds needed to stabilize all voltages. The
CLIP PROT LEDs will then turn off meaning that the amplifier is now operative.
In a complete audio installation, it is important to start up the equipment in the following
sequence: sound sources, mixer, equalizers, active filters and finally power amplifiers. To turn
them off the sequence should follow an inverse pattern.
4.2. Input attenuators
This consists of rotative potentiometers, situated on the front panel (4,6).
These attenuators enable the connection of different types of mixing tables, independent
regulation level and loudspeaker connections that allow an inferior power level that the level
already supplied by the power amplifier at its maximum power, with no danger of damaging, by
careless handling, the volume of the pre-amplified mixer.
Inside the device's packaging you will find a little plastic bag containing 2 transparent
caps which protect the input attenuation settings from unwanted manipulation. These caps are
transparent in order to let you visualize the current settings.
Once inserted, they cannot be removed with bare fingers, for this purpose, a small
screwdriver is needed.
4.3. Indicators
The APA amplifiers are equipped with a simple but efficient combined indicators system.
Indicator CLIP/PROT (2, 8) function as PROTECTION indicator.
They point to the lack of signal at the speaker outputs. These indicators may light up
due to following reasons:
1. From the moment the machine is switched on, until stand by period finalise that is
necessary for the stability of the internal tensions of the power amplifier.
2. Because the amplifier output has short circuited.
3. If the amplifier is giving a continuous voltage or is of very low frequency, this could
damage the loudspeakers.
In any case, should these indicators permanently light up, it is a sign of malfunctioning
and its cause should be investigated.
CLIP/PROT indicators functioning as CLIP indicator.
These illuminate when the signal given to the loudspeakers is 1.5dB before the real clip.
This CLIP system takes into account the possible variations in the mains voltage always giving a
real indication even if the electric mains varies. It is normal that working at high power levels, the
CLIP indicators illuminate at the rhythm of the low frequencies which are the ones that passes
major energetic contents. Make sure these indicators are not permanently illuminated.
