6
3.5. Limiter circuit
This system is an always active protection inside the XPA series of amplifiers. The ANTICLIP circuitry
constantly analyses harmonic distortion caused by excessive signal excursion at the power amplifier's output and
automatically reduces the input level in order never to exceed 0,5% total harmonic distortion.
The great convenience of such a circuit in any kind of installation has to be remarked: The clear advantage
of a limiting system in front of conventional compressors is that the former does practically not alter the dynamic
range, acting only when the distortion threshold is reached.
3.6. Output connections
See diagram 6.1 for output connection possibilities
The output section on the rear panel features both Speakon® connectors (13) and threaded connection
posts (14).
If you need to operate the amplifier in BRIDGED mode, you should place the “MODE” (10) switch in
BRIDGE position. Input signal should be fed into Channel 1 of the amplifier and the output appears at the 2+ and 2-
pins of the Speakon® connector and/or at the red connection posts.
ATTENTION: Terminals 1+ and 1- should only be used in case of “STEREO” or “PARALLEL” mode and
terminals 2+ and 2- in “BRIDGED” mode. Any other combination may impair final audio quality
When operating in BRIDGED mode, always make sure that the resulting load impedance of the installation
is never below 4
Ω
.
The connection cable that joins the amplifiers outputs and the loudspeakers must be of good quality,
sufficient section and as short as possible. This is most important when the distances to cover are long ones i.e. up
to 10 meters it is recommended to use a section not inferior to 2.5mm
2
and for superior distances 4mm
2
.
4. OPERATION AND USAGE
4.1. Start up
Pushing the switch button (5) lights up the integrated pilot light and both red "PROT" (4) LEDs during the
approximately 10 seconds needed to stabilize all voltages. The "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 (1).
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.
