Oxmoor MPM-81 User Manual

The MPM-81 Microphone Preamp Mixer
provides eight balanced microphone/
line level inputs. Each input can be
switched between microphone level or
line level.

There are eight Direct outputs and one
Mix Bus out. Each input can easily be
routed to the Mix Bus using a dedicated
control line for remote applications or
an internal dip switch for permanent
assignment. Any combination of the eight
inputs can be assigned to the Mix Bus.

The MPM-81 is ideal for use as an 8x1
mic/line mixer or as an 8x1 source selec­tor. It may also be used as an eight micro­phone preamp input with eight direct
outputs while using the Mix Bus as a
monitor output.

Each input has a selectable Hi-Pass filter
that can be switched in or out. This Hi­Pass filter can be used to reduce low
frequency noise from the microphone or

line inputs. Each input also has a ± 15 dB

trim pot which is located on the rear of
the unit. The trim pot can be used for
adjusting the microphone or line level
inputs for varying input signal levels. A
version of the MPM-81 is available with
input transformers.

All inputs and outputs are electronically
balanced and accommodate either bal­anced or unbalanced lines. Each output
provides Peak and Signal LED indica­tors. In addition, cage clamp connectors
are used to ensure easy installation and
solid electrical connections for the eight
program channel inputs and outputs and
the Mix Bus output.

Any input can be assigned to the Mix Bus
independent of other channels. Each
channel that is assigned to the Mix Bus
goes through its own VCA level control
and peak limiter. The VCA level control
for each channel is located on the front
panel of the MPM-81. The Mix Bus pro­vides a master VCA level control which
is also on the front panel of the MPM-81.

The Mix Bus has separate high frequency
and low frequency tone controls. The 8
kHz high frequency tone control pro-

vides a ± 12 dB boost or cut, and the low

MPM™-81

MICROPHONE PREAMP/MIXER

HI PASS

MIC/LINE

TRANSFORMER

OPTION

CH. 1

TRANSFORMER

OPTION

CH. 2

TRANSFORMER

OPTION

CH. 3

TRANSFORMER

OPTION

CH. 4

TRANSFORMER

OPTION

CH. 5

TRANSFORMER

OPTION

CH. 6

TRANSFORMER

OPTION

CH. 7

TRANSFORMER

OPTION

CH. 8

FILTER

HI PASS

MIC/LINE

FILTER

HI PASS

MIC/LINE

FILTER

HI PASS

MIC/LINE

FILTER

HI PASS

MIC/LINE

FILTER

HI PASS

MIC/LINE

FILTER

HI PASS

MIC/LINE

FILTER

HI PASS

MIC/LINE

FILTER

ON

CH.

12345678

SW 9 SW 10 SW 11 CONTROL PORT

MPM-81 Microphone Preamp/Mixer

frequency 150 Hz tone control provides

a ± 12 dB boost or cut. Adjustment of

the tone controls is made using front
panel knobs.

Each channel can be assigned to the Mix
Bus either by providing a maintained
contact closure on the channel’s MIX
control line, or by using the internal dip
switch to permanently assign channels
to the Mix Bus. The MIX control line for
each channel is located within the
channel’s input/output cage clamp on
the rear panel.

The MPM-81 provides a Page feature
that allows one of the input channels
to be used as a page input. This Page
feature is only available through the
Mix Bus output and does not affect the
Direct output.

When using this Page feature, all chan-

TRIM CONTROL

TRIM CONTROL

TRIM CONTROL

TRIM CONTROL

TRIM CONTROL

TRIM CONTROL

TRIM CONTROL

TRIM CONTROL

12345678

VCA / LIMITER

VCA / LIMITER

VCA / LIMITER

VCA / LIMITER

VCA / LIMITER

VCA / LIMITER

VCA / LIMITER

VCA / LIMITER

ON

CH.

12345678

TONE CONTROL BY-PASS

PEAK

SIGNALPEAK

BAL/UNBALANCE

SIGNALPEAK

BAL/UNBALANCE

SIGNALPEAK

BAL/UNBALANCE

SIGNALPEAK

BAL/UNBALANCE

SIGNALPEAK

BAL/UNBALANCE

SIGNALPEAK

BAL/UNBALANCE

SIGNALPEAK

BAL/UNBALANCE

SIGNALPEAK

BAL/UNBALANCE

SIGNAL

BAL/UNBALANCE

MIX ASSIGN

DIRECT OUT

MIX ASSIGN

DIRECT OUT

MIX ASSIGN

DIRECT OUT

MIX ASSIGN

DIRECT OUT

MIX ASSIGN

DIRECT OUT

MIX ASSIGN

DIRECT OUT

MIX ASSIGN

DIRECT OUT

MIX ASSIGN

DIRECT OUT

ON

CH.

VOLUME CONTROL

••••••••

•••••••

nels can be assigned to the Mix Bus
except the channel that is selected as
the Page channel. When the Page chan­nel is activated, it is routed to the Mix
Bus. All channels except the Page chan­nel will then mute their audio if they
have been programmed to mute. Upon
completion of the page, all channels
return to their previous levels.

A control port provides connection for
remote volume control of channels 1 - 8
and the Mix Bus master volume. Each
remote volume control requires a 10K
pot and a DC voltage between +15
“Off” and 0 VDC “Full On.”

The compact 1U rack space MPM-81
brings simplicity to system design,
installation and operation, along with
the uncompromising performance and
reliability for which Oxmoor products
are known.

MIX OUT

CH. 1

CH. 2

CH. 3

CH. 4

CH. 5

CH. 6

CH. 7

CH. 8

Oxmoor Corporation, LLC, 309 Cahaba Valley Parkway, Birmingham, AL 35124 USA Toll Free: 1-800-262-6898

Phone: [phone] Fax: [phone] E-mail: [e-mail] Internet: www.oxmoor.com

MPM-81™ SPECIFICATIONS

FREQUENCY RESPONSEFREQUENCY RESPONSE

FREQUENCY RESPONSE 20 Hz to 20 kHz ...................................................................... +0, -0.3 dB (Ref. +4 dBu)

FREQUENCY RESPONSEFREQUENCY RESPONSE
HUM AND NOISEHUM AND NOISE

HUM AND NOISE Ref. +4 dB, Input Terminated With 150 ohms,

HUM AND NOISEHUM AND NOISE

Output @ Unity Gain (20 Hz to 20 kHz, Unweighted)

Line Input, Direct Output ....................................................... -93 dBu

Microphone Input, Direct Output .......................................... -85 dBu

Line Input, Mix Output............................................................ -84 dBu

Microphone Input, Mix Output............................................... -80 dBu

DISTORTIONDISTORTION

DISTORTION THD + Noise and IMD*, Ref. 0 dB, Output @ Unity Gain

DISTORTIONDISTORTION

Line Input, Direct Output ....................................................... .01%

Microphone Input, Direct Output .......................................... .01%

Line Input, Mix Output............................................................ .035%

Microphone Input, Mix Output............................................... .035%

OFF ISOLATIONOFF ISOLATION

OFF ISOLATION Line Input Ref. 0 dBu ............................................................. 8 0 dB

OFF ISOLATIONOFF ISOLATION

Microphone Input Ref. -40 dBu............................................. 80 d B

CROSSTALKCROSSTALK

CROSSTALK Unity Gain, Ref. +4 dB output

CROSSTALKCROSSTALK

Channel to Channel ................................................................ -80 dB (20 Hz to 20 kHz)

MIC/LINE INPUTSMIC/LINE INPUTS

MIC/LINE INPUTS Type........................................................................................... Electronically Balanced (RF Suppressed)

MIC/LINE INPUTSMIC/LINE INPUTS

Connectors ............................................................................... Cage Clamps with Mating Connector

Input Impedance ..................................................................... 10 K Oh ms

Line Input Sensitivity .............................................................. Typical +4 dBu, Maximum +18 dBu

Microphone Input Sensitivity ................................................. Typical -40 dBu, Maximum -22 dBu

Mic/Line Switch....................................................................... Sets Input for Microphone or Line-Level Source

Mic/Line Trim Control Range ................................................ ± 15 dB (Ref. 0 dBu Output)

PROGRAM OUTPUTSPROGRAM OUTPUTS

PROGRAM OUTPUTS Type ........................................................................................... Electronically Balanced (RF Suppressed)

PROGRAM OUTPUTSPROGRAM OUTPUTS

Connectors ............................................................................... Cage Clamps with Mating Connector

Source Impedance .................................................................. 150 Ohms (75 Ohms/Side)

Recommended Load Impedance ........................................... 600 Ohms or Greater

Maximum Output Level........................................................... Ref. 1 kHz @ Rated THD

Terminated w/600 Ohms .................................................... +24 dBm (All Outputs Driven Simultaneously)

Unterminated......................................................................... +26 dBu

TONE CONTROLSTONE CONTROLS

TONE CONTROLS Hi-Frequency ............................................................................ 8 KHz, ±12 boost/cut

TONE CONTROLSTONE CONTROLS

Low-Frequency ......................................................................... 150 Hz, ±12 boost/cut

DUCK ATTENUATIONDUCK ATTENUATION

DUCK ATTENUATION Fixed .......................................................................................... -80 dBu

DUCK ATTENUATIONDUCK ATTENUATION
CONTROL PORTCONTROL PORT

CONTROL PORT Connector ................................................................................. 25-pin D-sub, Female

CONTROL PORTCONTROL PORT

VCA Control .............................................................................. +15 VDC “OFF” to 0 VDC “Full ON”

Slope ......................................................................................... 1 dB/65 mV

MIX CONTROLMIX CONTROL

MIX CONTROL Connectors ............................................................................... Cage Clamps with Mating Connector

MIX CONTROLMIX CONTROL

Logic Action.............................................................................. Maintained Closure to Common

Logic Levels ............................................................................. Low < .8 Volts, High > 2.4 Volts

Maximum Sink Current ........................................................... 1 mA

Maximum Cable Length .......................................................... 600 m (2000 ft.), #22 AWG

Switching Time ........................................................................ 50 ms

MAINS POWERMAINS POWER

MAINS POWER Power Requirements ............................................................... 100 to 125 VAC or 200 to 230 VAC, 50/60 Hz

MAINS POWERMAINS POWER
MECHANICALMECHANICAL

MECHANICAL Overall Dimensions ................................................................. 44mm H x 482mm W x 254mm D

MECHANICALMECHANICAL

(1.72” H x 19” W x 10” D)

Finish ........................................................................................ Textured Black Paint

Weight ....................................................................................... Shipping: 6.3 Kg (14 lb.)

Net: 5.9 Kg (13 lb.)

Specifications subject to change without notice. *SMPTE Method; 60 Hz +7 kHz mixed 4:1.

Oxmoor Corporation, LLC, 309 Cahaba Valley Parkway, Birmingham, AL 35124 USA Toll Free: 1-800-262-6898

Phone: [phone] Fax: [phone] E-mail: [e-mail] Internet: www.oxmoor.com

REV: 1.4 - 8/01