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Power
ATTENTION:
•
The amplifier must be powered on last.
•
L'amplificateur doit être mis sous tension en dernier.
Reconnect all power cables and switch on all other equipment before powering on the power
amplifier. The front panel power LED of the amplifier lights green.
B
IEC power connector (see
100 - 240 VAC, 50-60 Hz mains power supply.
C
AC mains switch — Toggle this switch between power on and power off.
Indicators and Settings
D
Channel Status LEDs — Four (XPA U 2004 FX) or eight (XPA U 2008 FX) pairs
of LEDs provide feedback about the status of each channel. They have the same
function as the corresponding front panel LEDs.
The upper Limiter/Protect (
mode, triggered by any of the limiter protection circuits:
Excessive clipping (providing sufficient warning before the transformer cores in a
•
high impedance speaker system saturate).
•
Short circuit on output
The lower Signal LEDs (
threshold.
E
Attenuators
Each channel has its own potentiometer that goes from full attenuation
(∞, fully counterclockwise) to no attenuation (0 dB, fully clockwise). Each
potentiometer is detented to more easily set the input signal level of
multiple channels to the same level of attenuation, and laser-etched to
indicate position. Use a small screwdriver (such as the provided Extron
Tweeker) to adjust the audio input level for the corresponding channel.
For information about adjusting the attenuation level of the XPA U amplifier, see
on page 13.
F
Output Mode Selection Switch — This switch determines the function
of each amplifier channel. There are six settings: two low-impedance (8
ohms, 4 ohms) and four high-impedance modes.
Low-Impedance Modes (8 ohm/4 ohm):
The 8 ohm stereo setting is used when connecting to 8 ohm speaker
loads, and the 4 ohm setting is used when connecting to 4 ohm loads.
High-Impedance Modes:
There are four high-impedance modes available: 70V, 70V (HPF OFF), 100V, 100V
•
(HPF OFF). These modes are used when connecting to distributed 70 volt or 100 volt
loudspeaker systems.
•
In the 70V and 100V modes, an 80Hz, 12 dB/octave high-pass filter is applied to the
signal, to prevent saturation of the transformer cores in the speakers.
•
In the 70V (HPF OFF) and 100V (HPF OFF) modes, the high-pass filter is disabled. The
(HPF OFF) modes should only be used when a high-pass filter will be applied in a DSP
upstream of the amplifier.
figure
6, on the previous page) — Connect this socket to
LIM/PRT ) LEDs light red when the channel is in protection
SIG ) light green when the input signal crosses the signal detection
XPA Ultra FX Series Power Amplifiers • Operation
LIM/
PRT
SIG
10
12
8
6
14
18
4
1
26
2
∞
0
ATTENUATION
Operation
(HPF OFF)
70V
70V
8
100V
4
100V
(HPF OFF)
OUTPUT MODE
10
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