LD PA 400, User Manual

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1 2 3 4 5 6 7 8 9 10 11 12 13
1, 13. Air Outlets
The fresh air drawn from the front intake is exhausted here. A good circulation should be provided. (See “SETUP”)
2. Switch for Stereo or Mono Bridge Mode.
(See “Stereo/Mono Bridge Mode”)
3, 11. Unbalanced jack socket channel “B” (3), unbalanced jack socket channel “A” (11)
4,10. Balanced XLR input channel “B” (4), balanced XLR input channel “A” (10)
The power amplifier has 2 input sockets for each channel, unbalanced jack and balanced XLR. Both are connected in
parallel and therefore can be used to link the signal through.
5,6,7,8. Speaker Connectors.
For each channel there are two ways to hook up speaker cabinets. 5 and 7 are “Binding Posts”. They allow direct
connection of the speaker cable by clamping the speaker cable cores into the binding posts. If using this set-up
ensure that all strands are well twisted and there is no loose wire or you will create a short circuit. In addition each
channel has a Speakon connector (6,8). This is wired 1+ and 1-. Connector OUT 1 (8), the output of channel “A”,
additionally carries the signal of channel ”B” wired to pins 2+ und 2-, so if you are using the power amplifier in
conjunction with an active crossover you only have to use a single 4-wire speaker cable to hook up the speaker
cabinet.
Caution! Speaker outputs never must be paralleled. Therefore never link the two red binding posts nor connect a
red with a black binding post.
9. Fuse
The PA-series amplifiers are equipped with a reset-able fuse. In most cases there is a reason if the fuse trips. If
this happens switch off the power, reset the fuse and switch on the power again. If the fuse repeats to trip, the unit
is faulty and needs service by an authorized service department. Never try to restrain the reset knob.
12. Ground Lift Switch
In cases where two or more mains supplied appliances are liked together with a screened audio cable a ground loop
may occur. The typical resulting effect is a deep humming noise. The ground lift switch disconnects the electronic
earth and the chassis ground and in that way the hum is removed.
Stereo/Mono Bridge Mode
Switch (2) controls the operating mode of the amplifier.
Stereo : Both channels independently receive their signal from the corresponding input socket.
Mono Bridge Mode: To increase the total power output of the amplifier both channels are linked together in a special
way. The input signal is fed exclusively via socket 10 or 11. The volume control of channel “A” sets the loudness. The
speaker cabinets are connected to the red binding posts only. Channel “A” delivers the positive phase whereas
channel “B” provides the negative one. None of them must be connected to ground. If you prefer the Speakon output,
use a 4 pole connector and socket OUT1 (8). Connect in the following way: Positive pin 1+, negative pin 2+.
Please refer
to the technical data sheet for minimum impedances in the Mono Bridge Mode.
REAR PANEL