MA-1212 Mixer Amplifier
120-Watt, 12 Input
Mixer Amplifier
General Description:
The Electro-Voice ® MA-1212 is a 120-watt, twelve-input
mixer amplifier designed for commercial sound
applications. It features twelve separate input controls
which can be used to adjust the level from any of 12 input
sources. Figure 1 shows the layout of the front and rear
panels.
Input channels 1-10 are designed to either be used as
low-Z balance microphone or line level inputs. The
combination connector on inputs 1-10 permits use of either
XLR or ¼” input connectors. The block diagram shown in
Figure 2 outlines the signal flow for the MA-1206. A signal
appearing at either input 1 will automatically mute the other
channels unless the mute function is defeated via a switch
on the rear panel.
at the paging input, it shall automatically mute other input
sources. The paging input shall be equipped with its own
gain control. There shall be a master level control. Separate
bass and treble equalization controls shall be provided. The
mixer amplifier shall meet the following performance criteria:
output power shall be 120 watts; total harmonic distortion
shall be less than 1% at 1 kHz; frequency response shall be
within 3 dB from 50 Hz to 15 kHz; input impedance shall be
600-ohms (balanced inputs) or 47 kW (unbalanced inputs);
nominal load impedance shall be 4-, 8- or 16-ohms for voice-
coil-connected loudspeakers, 25, 70.7 or 100-volt nominal
transformer windings for the constant-voltage output.
Inputs 11 and 12 are for auxiliary line-level sources such
as tape or CD players. Mono or stereo signals may be
applied to inputs 11 or 12. The left and right components
of a stereo signal can be applied to the dual RCA phono
jacks of these inputs and mixed together to drive the built-
in monaural power amplifier. A rear panel paging input
with gain control is provided for the paging output of a
telephone system. An audio signal appearing at this input
automatically mutes all other inputs. A preamplifier output
jack and power amplifier input jack permit the mixed output
to be fed to an external signal processor (graphic EQ or
compressor), and then returned to the built-in amplifier.
The preamp output may be used to drive an additional
power amp with its own set of speakers without interrupting
the function of the built-in amplifier.
In addition to a preamplifier output/power amplifier input link,
there shall also be a line-level balanced XLR output. The
mixer amplifier shall operate from either a standard 120 V
ac 50/60 Hz or a 24V dc power source, and measure 13.3
cm (5.2 in.) high x 48.0 cm (18.9 in.) wide x 32.0 cm (12.6
in.) deep. The net weight shall be 11.5 kg (25.4 lb). The
mixer amplifier shall be the Electro-Voice ® Model MA-1212.
There is also a 24v dc power option to operate the unit off
of a 24v emergency power source. The speaker output is
available at a barrier strip, which includes terminals for
driving low impedance loudspeaker loads, as well as 25,
70.7 or 100 volt distributed systems.
Architects’ and Engineers’ Specifications:
The mixer amplifier shall have twelve input channels, with
individual mix gain controls. Input channels 1 through 10
shall be configured for either low-Z balanced microphone
operation or hi-Z line level signals via switches on the rear
panel. A signal present channel 1 shall trigger the muting
of channels 2-12. The mute circuit shall be defeatable using
a switch on the rear panel. Inputs 1 - 10 shall be available
via combination female XLR / ¼” connectors. Inputs 11
and 12 shall accept either monaural or stereo sources. If
a stereo source is connected, it shall be properly mixed to
mono via a resistor network mounted on the input plate.
There shall be a paging input that accepts a 600-ohm line-
level feed from a phone system. When a signal is present
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