Bogen MXM A Operating Manual

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BOGEN®

MODEL MXM-A
MIXER _ PREAMPLIFIER

LEAR SIEGLERJNC. @
®
BOGEN DIVISION

PO. BOX 500
PARAMUS, N. J. 07652

. INSTALLATION ANII OPERATING MANUAL

READ THOROUGHLY BEFORE OPERATING EQUIPMENT

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DESCRIPTION

The Bogen Model MXM-A is aprofessional broadcast
quality, self-powered mixer-preamplifier. It is designed
for use in theatres, radio stations, recording studios
and public address applications. The output may be
used to feed booster amplifiers or a low impedance
500/600 ohm transmission line by means of a 500/600
ohm plug-in transformer.

The preamplifier will accept seven input signals. All
inputs may be mixed and faded, and the volume of each,
except the bridging input/output, may be controlled
indivrdually or simultaneously with the master volume
control. All five microphone channels are high impe-
dance but can be converted to low impedance bythe
use of plug-in transformers. One microphone input con-
verts to an equalized input for a magnetic phono cart-
ridge or tape playback head. Two auxiliary inputs, both
high impedance, high level, are connected to a fader
control. A bridging input accepts signals from a remote
preamplifier or a zero level line. Where additional in-
puts are required, up to three MXM-As may be paral-
leled to accommodate as many as 21 inputs. The master
gain control may be used to adjust the output level of
the mixed program.

The output level may be monitored visually with a
built-in Db meter and aurally from a headset monitor
jack. A meter sensitivity control on the front panel pro-
vides calibrated meter readings for 500/600 ohm output
or full-scale readings on weak signals. Provision is
also made for monitoring of the 25 volt or 70 volt out»
puts of a separate booster amplifier.

Each of the five microphone input channels is equip-
ped with a separate music-speech filter switch, which

POWER OUTPUT: At 20 V into high impedance load
at 1% distortion; at4 V into 600 ohms (with plug-
in transformer) at 1% distortion; at 0.1 V into 1
meg ohm from bridging output.

FREQUENCY RESPONSE: 18 to 38,000 cps, :1 db.

OUTPUTIMPEDANCE: Highimpedance less than 3,000
ohm; 500/600 ohm with TL600 (broadcast quality)
plug-in transformer.

INPUT SENSITIVITY: High impedance 2 MV; Low
impedance 0.1 MV; Mag/Tape 1 MV; Aux 0.1 V;
Bridging 0.5 V.

SPECIFICATIONS

may be set to provide a fixed, low-frequency attenuation
for the particular input. This selective filtering helps
to overcome poor room acoustics and increases speech
intelligibility by improving individual microphone res-
ponse. Included also are separate bass and tone controls
to adjust the frequency response of the mixer.

The input channels, except the bridging input and
MIC 5, may be provided with remote control and/or mi-
crophone precedence control. This is accomplished by
using Bogen accessories SR-2, SR-4 and RVC-2 remote
volume controls and a LVP-l plug-in unit plus a cus-
tomer supplied switch.

Another Bogen accessory, the WMT-l transformer,
enables the pre-amplifier to accept inputs from abal-
anced 500/600 ohm telephone line, such as a Musak
transmission cable. The input, at zero level, is fed
into one of the two auxiliary receptacles.

Acoustical problems are relieved and intelligibility
is assured through the use of a unique, calibrated low
frequency (notch) filter which introduces a sharp notch
at the selected frequency without affecting the rest of
the audio range. This control effectively eliminates hum,
turntable rumble and other undesirable noises without
affecting overall amplifier response.

An excellentsignal-to-noise ratio, coupled with high
microphonesensitivity and DC filament voltages, pro-
vide professional quality satisfactory for the most cri-
tical applications. Conservatively rated components,
thoroughly proven circuit techniques and the use of life-
time silicon rectifiers in thepower supply assure high-
est reliability of performance.

HUM (below rated output): Microphone ~60db.

TONE CONTROL ACTION: Treble (10 KC) +12 db to
-12 db; Bass (50 cps) +14 db to -8 db.

TUBES: Total of 6; 4 - 12AX7A, 1 -7247, 1 -12AU7A,
plus 3 silicon rectifiers.

POWER CONSUMPTION: 26 watts at 117 VAC. 50/60
cps.

OVERALL DIMENSIONS: 16%wide, 12 deep, 4%
high.

SHIPPING WEIGHT: 23 lbs.