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3. BUS Line Inputs / Outputs
The MA1240a has two common or BUS inputs that
receives audio signals from standard line-level audio
sources and sends them to any or all channels. The BUS
line outputs are direct feed-through to allow the BUS
inputs to be fed to other amplifiers. Be sure to use high
quality RCA cables that feature low impedance, shielding
and high quality connectors.
4. Remote Turn-On Switch
This switch selects the turn-on stimuli that will put the ampli-
fier in ready mode. “Trigger” setting relies on 3-30V AC/DC
voltage going into the trigger input to activate the amplifier.
“Auto” setting senses a signal on the RCA line-level inputs
and automatically puts the amp in ready mode. “On” setting
puts the amp constantly in ready mode so that it can be
controlled by the master power switch on the front panel.
In “Auto” mode, the amplifier will take approximately 15
minutes to return from ready to standby mode.
5. Trigger Input / Output
The trigger input is a handy feature when connecting the
amplifier to an automated audio system. The 3.5mm mini-
plug jack will accept a 3-30V AC/DC output from another
device, or from a separate power supply. When the trigger
input is energized, the amp turns from standby to ON mode.
When using the MA1240a with a receiver without a trigger
output, the voltage can come from a 12V wall wart (3.5mm
tip-positive connector) plugged into the receiver’s switched
outlet and the trigger input. The MA1240a can also provide
an output trigger voltage (12DC @500mA max.) to turn on
and off other devices in the audio system. When the ampli-
fier turns off (standby mode), the voltage will drop to zero.
Note: Remember there is a delay of approximately 15
minutes before the amplifier goes to standby when using
the “Auto” turn-on mode.
6. Channel Gain Control
Each channel has its own independent level adjustment.
This allows the output level of each speaker to be per-
fectly matched to its area. It can also be used to limit the
maximum audio level in a certain area.
7. Bridging Switch
By simply flipping a single switch, two channels can be
combined to increase the total power output. This is helpful
when extra power is needed in certain areas.
Note: The minimum impedance for bridged channels is 8
ohms. Also, please observe the proper speaker wiring when
bridging channels. Input selection and volume settings for
bridged channels will be controlled by the left channel. “BR”
is bridged mode and “ST” is non-bridged or stereo mode.
CAUTION: Only change switch positions when the
amplifier is turned off.
8. Input Selection Switch
Each channel is capable of delivering the source from
many inputs. The three main inputs are BUS 1, BUS 2
and LINE IN. The selection for these inputs is done via
the Input Selection switch associated with each channel.
Select the desired source input. Set the Input Selection
switch to BUS 1 (will play source connected to the BUS
1 input), BUS 2 (will play source connected to the BUS
2 input) or LINE IN (will play source connected to that
channel’s LINE IN).
CAUTION: Only change switch positions when the
amplifier is turned off.
9. Speaker Output Terminals
The MA1240a uses high quality Phoenix style connectors
for the speaker connections. Use 14-18 gauge stranded
two-conductor loudspeaker wire. Ensure that at least
2 inches of each conductor are separated. Strip away
¼ inch of insulation from each conductor. Connect the
appropriate conductor to each screw terminal, observing
correct polarity. Also, please observe proper speaker wir-
ing when bridging channels.
10. Individual Channel Input
All twelve channels have their own dedicated input that
allows the connection of audio sources in addition to
the common BUS inputs. This is useful when using the
MA1240a with an audio matrix switcher.
11. AC Voltage Switch
The unit is set at the factory for 115V U.S. operation; simply
connect the included IEC power cord to your wall outlet.
For 230V operation, move the voltage selector switch to the
230V position. When operating at 230V the internal fuse
located in the IEC socket should also be changed. In most
230V applications a separate power cord will be required
and is not included.
12. IEC Power Connector
The unit comes with an IEC jack that permits removal of
the AC power cord. This allows the flexibility of changing
the power cord for different countries. The IEC socket
also houses the main fuse holder. Plug the power cord
supplied with the amplifier into the amplifier and wall
outlet or appropriate surge protector.
CAUTION: DO NOT plug the amplifier’s power cord into
a switched outlet, such as what is provided on some Sur-
round Receivers. If you wish to have the amplifier turn on
when the Receiver is powered up, use one of the power
modes, such as Trigger or Auto.
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