Power Supply; Operation; Selecting The Operating Mode; Selecting The Filter - IMG STAGELINE STA-900A Mode D'emploi

5.3 Power supply

Connect the mains cable to the mains jack
(13) and then to a mains socket (230 V/ 50 Hz) .

6 Operation

6.1 Selecting the operating mode

Use the switch MODE (10) to select the
operating mode .
Stereo mode
In the stereo mode, the two channels are
operated independently .
Parallel mode
When using both amplifier channels to am-
plify the same input signal, select the parallel
mode and use the jack L-CH as an input . The
input signal will be internally routed to the left
channel and the right channel . A signal at the
right input will be ignored . The left control
L-CH is used to adjust the volume for both
outputs together . The filter (
is also selected by means of the switch and
the control of input L-CH for both channels
together .
Bridge mode (BRIDGE)
The bridge mode is used to obtain higher
power at a speaker . For this purpose, the two
amplifier channels are combined to a mono
amplifier . The input signal at the left channel
is additionally switched to the left channel
in an inverted way . Thus, the voltage at the
output will double if the speaker has been
connected for the bridge mode as described
in chapter 5 .2 . A signal at the right input will
be ignored . The volume is adjusted with the
left control L-CH .
10
PROTECT
LIMITER
SIGNAL
ACTIVE
L-CH
1 2
L-CH IN LINK
SUBWOOFER
P2
OUT
P3
P1 2 1 1 2
70 Hz 120 Hz
3 3
HPF 100Hz
BYPASS
R-CH IN LINK SUBWOOFER
P2
OUT
P3
P1
2 1 1 2 70 Hz 120 Hz
3 3
HPF 100Hz
BYPASS
4 5 6 7

6.2 Selecting the filter

The integrated filters can be used as a cross-
over network for 2-way speaker systems
(e . g . subwoofer/ satellites) . Use the switches
SUBWOOFER / PASS / HPF (7) to select the cor-
responding filter for the speaker connected .
Position SUBWOOFER
low-pass filter for a subwoofer; use the
control above (6) to adjust the crossover
frequency (70 – 120 Hz)
Position BYPASS
no filter for full range speakers
Position HPF
high-pass filter (100 Hz) for satellite
speakers
To suppress low-frequency interference (e . g .
impact sound, hum), use the switch LOW-
CUT (9) to activate a 30 Hz high-pass filter
for both channels together .
chapter 6 .2)

6.3 Switching on /off

☞
To prevent loud switching noise, always
switch on the other units of an amplifier sys-
tem before switching on the power amplifier
and switch off the power amplifier before
switching off the other units . Before switch-
ing on the amplifier for the first time, set the
volume controls (2) to the left stop (-80) .
Switch on the amplifier with the POWER
switch (3): The power LEDs ACTIVE light up
and the LEDs PROTECT also light up briefly
while the switch-on delay to protect the
speakers is active .
R-CH
L-CH
L-CH
GROUND
1+ 1-
OUT
POS NEG
R-CH
1+ 1-
POS NEG
ON OFF
BRIDGE
1+ 1-
BRIDGE
MODE
POS NEG
BRIDGE PARALLEL
R-CH
STEREO
OUT
LOW-CUT 30 Hz
ON OFF
8 9 10 11 12
PROTECT
STA-900A
LIMITER
SIGNAL
ACTIVE
2 1
CIRCUIT
BREAKER
230V~
50Hz
13 14

6.4 Adjusting the level

Control the output of the signal source to its
rated level (0 dB) or to the highest undistorted
output signal . Turn up the controls L-CH and
R-CH until the maximum desired volume is
obtained . When a certain volume level is ex-
ceeded, the LEDs SIGNAL will light up .
If the LIMITER LEDs light up, the limiter
circuit to prevent overload of the amplifier
is activated . To keep the original dynamics
of the music, turn back the control until the
LEDs are off or only light up briefly .
CAUTION Never adjust the amplifier to a
very high volume . Permanent
high volumes may damage
your hearing! Your ear will get
accustomed to high volumes which do not
seem to be that high after some time . There-
fore, do not further increase a high volume
after getting used to it .

6.5 Ground lift switch

If there is unwanted noise without any music
signal, this noise may be due to a ground loop .
Ground loops may occur when two units are
connected both via their signal ground and
via the protective conductor of the power
supply or via a conductive connection of their
housings in the rack . To separate this ground
loop, set the switch GROUND (8) to OFF . In
case of doubt, test both positions and leave
the switch in the position with the least noise .
ON
OFF
3