Apogee Sound CA8000DX Manuel d'instruction de l'utilisateur - Page 8
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3. Operation and Usage
3.1 Start Up
Pushing the POWER SWITCH illuminates the LED Power Indicator and activates the start-up sequence.
Initially, both red CLIP LEDs will illuminate during start-up, while the amplifier performs a diagnostic check
and stabilizes all internal voltages. After approximately 10 seconds, the CLIP LEDs will turn off indicating
that the amplifier is now ready for use.
In a typical audio system, it is important to start up the equipment in the following sequence to avoid transient
'pops' and 'clicks' that could damage your speakers: sound sources, mixer, equalizers, speaker processors
or controllers, and finally power amplifiers. To turn them off, the sequence should be performed in an inverse
pattern, i.e.: power amplifiers, speaker processors or controllers, equalizers, mixer, sound sources.
3.2 Input Attenuators
The input attenuators are high quality rotary potentiometers, located on the front panel. The attenuators are
calibrated in dB with '0 dB' representing maximum level (fully clockwise), and infinity representing full
attenuation (fully counter clockwise).
Inside the device's packaging you will find a 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, a small screwdriver
is required.
3.3 Indicators
The CA8000D-Series amplifier is equipped with a simple but efficient combined indicator system.
The 'CLIP' indicator functions as both a CLIP indicator and a PROTECTION indicator. When functioning as
a PROTECTION indicator, the LED may illuminate for any of the following reasons:
1. When the amplifier is first switched on, indicating that the start-up sequence is initialised. The indicator
will go out when the amplifier is ready for use.
2. If the amplifier output has been short circuited.
3. If DC or very low frequencies are present on the output that could damage the loudspeakers.
In any case, should the CLIP indicator remain lit, it is a sign of malfunctioning and the amplifier should be
scheduled for service.
When the CLIP indicator is functioning as a CLIP indicator it will illuminate when the output level to the
loudspeakers reaches -1.5dB below the actual clip point. Clipping is simply the inability of the amplifier to
deliver any more output power because it has reached its design constraints, and/or because the AC mains
voltage is substandard (sagging).
The CA8000D-Series CLIP indicator system takes into account the variations in the AC mains voltage,
always giving a true indication even if the AC voltage varies. When working at high levels with pop and rock
musical styles, it is normal for the CLIP indicators to illuminate briefly at the rhythm of the low frequencies.
Occasional clipping is not particularly harmful to low frequency loudspeakers, but can rapidly destroy mid
frequency and high frequency drivers. Heavy clipping should always be avoided. When an amplifier clips,
it produces a waveform that approximates a square wave. When clipping, the amplifier is 'telling' the
loudspeaker cone or diaphragm to move outward in an infinitely short period of time and to remain there in
stasis (no movement) for the duty cycle of the wavelength. Then, the amplifier 'tells' the loudspeaker to move
rearward, again in an infinitely short period of time, and remain there until the next cycle occurs.
Whenever a speaker cone or diaphragm is NOT moving, all of the electrical energy applied to it is converted
directly to heat instead of sound, resulting in a high likelihood of damage to the loudspeaker.
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