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6
OPERATION
Selecting the Operating Mode
Select the operating mode with the
MODE
selector switch: ST = stereo mode, PAR = parallel mode (XPA
1800/27000/3004) or BRI = bridge mode.
Adjusting the Level
1
First, set the volume controls of the preamplifiers to zero and turn the level controls of the amplifier to
mid-position. There should be no loud humming. Should humming persist, check the connection cables
between the preamplifier and the amplifier (switch off components before).
2
Adjust the level controls to the desired volume value. The LEDs
“-30 dB
” and
“0 dB
” show the adjusted
input level. In case of overload, the red
CLIP
indicator lights up. In this case, reduce the volume
correspondingly.
3
In parallel and bridge mode the level control for channel 2 is disabled. Volume adjustment is made with
the level control for channel 1. Model XPA-3004: In parallel and bridge mode the level controls for
channel 2 and channel 4 are disabled. Then, volume adjustment is made with the level control for
channel 1 and channel 4.
4
With the
SENS
selector switch on models XPA 1800/27000 the input sensitivity of the amplifier can be
matched to the output level of the preceding unit: 1.4 V or 0.775 V are selectable.
Switching On/Off
1
To prevent loud switching noise, always switch on all other units of the amplifier system before
switching on the power amplifier. After operation, switch off the power amplifier first. Prior to switching
on set all level controls to the left stop position and make sure that the operating mode selector switch
MODE
is set to the correct position.
2
Switch on the amplifier with the power switch. The protection indicators
PROT
light up for about 10
seconds. If they do not, check if the amplifier is connected to the mains correctly. After the turn-on delay
the speakers are activated (protection indicators
PROT
are off). Afterwards the
POWER
indicator lights
up and indicates that the amplifier is switched on.
Switching on the Limiter
(XPA 350/700/1000/1200)
The integrated limiter reduces the input signal if a limit level at the output is reached. This will prevent
distortions and protect the connected speakers. With the selector switch LIMITER on models XPA
350/700/1000/1200 it is possible to switch the limiter circuit on and off.
Ground Lift Switch
(XPA 350/700/1000/1200)
If an interfering hum noise can be heard without a music signal, a ground loop may be the reason for this.
The ground lift selector switch on models XPA 350/700/1000/1200 allows for interrupting the ground loop
and the humming should be eliminated. For this purpose the set the selector switch to position LIFT. Thus
signal ground and housing ground are separated.
Protective Circuits
The integrated protective circuits prevent damage to the speakers and the amplifier. If activated, the
speakers are electrically separated from the amplifier and the protect indicator
PROT
lights up.
