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3 Applications
This PA stereo amplifier is especially designed
for applications on stage and in the discotheque.
It can be used in stereo operation, in mono par-
allel operation or in mono bridge operation. Both
channels have a tunable filter with a wide adjust-
ing range. The filters can be used as a crossover
network to use the amplifier channel e. g. for a
subwoofer only or for the high range only. Exten-
sive protective circuits protect the amplifier and
the speakers connected. Two powerful, temper-
ature-controlled fans provide the necessary
cooling of the amplifier.
4 Placing the Amplifier
The amplifier is provided for insertion into a rack
for units with a width of 482 mm (19"), but it can
also be used as a tabletop unit. In each case air
must be allowed to flow freely through all venti-
lation slots so that a sufficient cooling of the
amplifier is ensured.
4.1 Rack installation
For rack mounting 2 rs (rack spaces) = 89 mm
are required. The heated air blown out by the
amplifier at the rear must be able to dissipate
from the rack, otherwise a heat accumulation will
occur in the rack which may not only damage the
amplifier but also other units in the rack. In case
the heat is not dissipated sufficiently, a fan unit
has to be inserted into the rack.
To prevent top-heaviness of the rack, the
amplifier must be inserted in the lower part of the
rack. To ensure a safe fixing, the front panel
alone is not sufficient. In addition, the unit must
be fastened at the rear side or be supported by
means of lateral rails or a bottom plate.
5 Connections
Prior to connecting units or changing existing
connections, switch off the amplifier and the
units to be connected.
1) Connect the output of a preamplifier or a
mixer to the 6.3 mm jacks INPUTS (8) or the
XLR jacks (10). The jacks are designed for
balanced signals; the pin configuration is
shown in fig. 2. For connection of sources
with unbalanced signals 2-pole 6.3 mm plugs
may be used or adapters with the XLR con-
tacts 1 and 3 bridged.
The input signal should have line level. For
rated power of the amplifier an input signal of
1 V is required as a minimum.
For bridge operation or parallel operation
only connect the input of the left channel
L-CH.
As the XLR jacks and the 6.3 mm jacks of
the same input are directly connected in each
case, they can also be used for passing on
the signal e. g. to an additional amplifier.
2) The maximum output power is reached in
stereo operation and in parallel operation
when connecting 4 Ω speakers (minimum
admissible load impedance). It is also possi-
ble to connect 8 Ω speakers, however, in this
case the output power will slightly be
decreased. In bridge operation the maximum
output power will be reached with an 8 Ω
speaker (minimum admissible load imped-
ance in bridge operation). The required
power rating (P
) of the speakers is listed in
MIN
the table fig. 3.
8
For stereo operation or parallel opera-
tion connect the speakers to the speaker
jacks (16, 19), pin configuration of the plug
see fig. 2, or to the screw terminals (17, 18).
After inserting a speaker plug into the jack,
turn the plug clockwise until it locks into
place. For removing it later, retract the latch
lock at the plug and turn the plug counter-
clockwise.
If the screw terminals are used, ensure
that the cable ends are not stripped too far
and that no bare wires protrude (hazard of
contact and short circuit).
When connecting the speakers, pay atten-
tion to the same polarity of all speakers.
For bridge operation connect the positive
pole of the speaker to the positive terminal
(18) of the left output L-CH and the negative
pole of the speaker to the positive terminal of
the right output R-CH (17). (By signal inver-
sion in bridge operation, the positive terminal
of the right output becomes the negative con-
nection for the speaker.) The speaker can
alternatively also be connected to the
speaker jack BRIDGE (20) [pin configuration
of the plug
fig. 2].
Table fig. 3 also shows possibilities of con-
nection for several speakers to one output. In
each case it is stated which power rating
(P
) each speaker must have as a mini-
MIN
mum with the corresponding impedance (Z).
When interconnecting several speakers, spe-
cial attention has to be paid to the correct
connection of the positive and negative ter-
minals.
Important: The total impedance at each out-
put must not fall below 4 Ω in stereo operation
and parallel operation and must not fall below
8 Ω in bridge operation!
3) Connect the plug of the mains cable (15) to a
socket (230 V~/50 Hz).
6 Operation
6.1 Selecting the operating mode
Select the desired operating mode with the
switch STEREO/ PARALLEL/ BRIDGE (12).
STEREO
Stereo operation – "
"
In stereo operation, both channels are operated
independently of each other.
PARALL
Parallel operation – "
"
The input signal is internally switched from the
left channel to the right channel in addition. A
signal at the right input is ignored. The volume is
adjusted for both outputs together with the left
control. Also the filter is adjusted (
6.2) via the switches and the control of the input
L-CH for both channels together.
BRIDGE
Bridge operation – "
"
The bridge operation serves to obtain a higher
power at one speaker. For this purpose both
amplifier channels are combined to a mono
amplifier: The input signal at the left channel is
additionally sent to the right channel in an
inverted way. Thus, the voltage at the output is
doubled if the speaker is connected for bridge
operation, as described in chapter 5. A signal at
the right input is ignored. The volume is adjusted
with the left control and the filter is adjusted at
the input L-CH (
chapter 6.2).
6.2 Filter
The integrated filter can be used as a crossover
network for 2-way speaker systems (e. g. sub-
woofer / satellite). Select the function correspon-
ding to the connected speaker with the switch
HIGH / BYPASS / LOW (9).
Position LOW:
Position HIGH:
Position BYPASS: no filter
Adjust the cut-off frequency of the filter with the
control CROSSOVER FREQ. (7). Select the
adjusting range with the switch (6) below it. To
prevent switching noise, only actuate this switch
with the filter switched off [sliding switch (9) in
position BYPASS].
Switch released "×1": 45 – 960 Hz
Switch pressed down "×10": 450 – 9600 Hz
When adjusting the frequency, consider the fre-
quency response of the connected speaker. The
operation of a speaker outside its frequency
range may lead to distortions and overload of the
speaker.
6.3 Switching on / off
To prevent loud switching noise always switch
on the power amplifier in an amplifier system
after all other units and switch it off as the first
unit after operation. Prior to the first switching on,
turn the volume controls (1) to the left stop "MIN".
Switch on the amplifier with the switch
POWER (5). After the welcome, first the display
(3) shortly shows the adjustments of the operat-
ing mode, the limiter and the input attenuation
(fig. 5) and then changes to the standard operat-
ing indication (fig. 4). After switching-on, the
LEDs PROTECT and LIMITER (2) light up for a
short time. During this time the switch-on delay
for the protection of the speakers is active.
6.4 Adjusting the level
Control the output of the mixer or preamplifier to
its rated level (0 dB) or the highest undistorted
output signal. Turn up the controls (1) so far until
the maximum desired volume is reached. The
ATTEN
attenuation "
controls is shown on the display (3) both numer-
ically (i) and graphically (j) for a few seconds
after changing the adjustment. Then the display
is changed to the standard indication again (fig.
4). The LEDs SIGNAL, -20 dB and -10 dB (2)
and a vertical bar (e) on the display show the
output level.
If the display shows
overloaded. If the LIMITER LEDs light up, the
limiter circuit is active and prevents the overload
of the amplifier (
back the corresponding control (1).
chapter
CAUTION Never adjust the amplifier to a
very high volume. Permanent high
volumes may damage your hear-
ing! The human ear will get accus-
tomed to high volumes which do
not seem to be that high any more
after some time. Therefore, do not
further increase a high volume
after getting used to it.
6.5 Power indication
The standard indication during operation (fig. 4)
shows the output power of both speaker outputs
in the first line (a). This value has been calcu-
lated according to the output voltage measured
low pass filter
(18 dB / octave)
high pass filter
(18 dB / octave)
" of the input signal by the
CLIP ON
, the input is
chapter 7). In both cases turn
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