Next LAs218 User’s Manual
www.next-proaudio.com
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Care should be taken to avoid amplifier clipping.
It is important to understand
that a low power amplifier driven into clipping is more likely to damage a loudspeaker than a
higher power amplifier used within its ratings
.
This is because music signals have a high
peak-to-average "crest" factor. When an amplifier is severely overdriven, its output
waveform is “clipped” (its peaks are squared off) – reducing the crest factor. In extreme
cases, the waveform can approach that of a square wave. An amplifier is normally capable of
producing far more power under these conditions than its undistorted rated power output.
The use of very high power amplifiers with outputs much greater than those recommended is
discouraged.
Care should also be taken to avoid switch-on surges, which can result in momentary
power peaks in excess of specified ratings. The PXA8000 element has a protection circuit to
avoid this between the integrated processor and amplifier. Nevertheless, this circuit only
works within the PXA8000 components, if you switch off your mixer or any other exterior
component the power surge will occur. When powering up a sound system it is important to
switch on the amplifiers last, after the mixer and control electronics have stabilised. When
powering down the system, reverse the sequence and switch off the amplifiers first.
TROUBLESHOOTING
Simple troubleshooting does not require sophisticated measurement equipment and
can be easily undertaken by users. The technique should be to segment the system in order
to identify the faulty system component: signal source, controller, amplifier, loudspeaker or
cables. Most installations are multi-channel. It is often the case that one channel works and
others do not. Trying different combinations of system elements can usually help to isolate
and locate the fault.
Some cabinet faults can be quite easily identified and corrected by the user. A simple
sweep with a sine wave generator can be very helpful though it MUST be made at a fairly
low level to prevent damage to the components. A sine wave sweep can help find:
Vibrations due to loose screws.
Air-leak noises: check that no screws are missing, particularly where the accessories
attach to the cabinet.
Vibrations due to a front grille badly positioned on the quick release fixings.
Foreign object that has fallen into the cabinet after repair or through the ports.
Internal connection wires or absorbing material touching the loudspeaker diaphragm:
check by removing the bass loudspeaker.
Loudspeaker not connected or phase reversed following a previous inspection, test or
repair.
