DESCRIPTION
Thank you for purchasing the Professional Sound Corporation
M4 A+ portable stereo audio mixer.
PSC is confident that
the M4 A+ has set new standards in portable mixing boards.
Please feel free to contact us if you have any comments orquestions about your mixer or have any suggestions about new
products you would like to see developed.
PSC extends a two year limited warranty on parts and labor
to all M4 A+ owners who return their warranty cards at thetime of purchase.
The warranty gives you specific rights
which are stated on the card and enables us to keep you
informed of product updates.
The PSC M4 A+ provides all the features necessary to produce
studio quality recordings in the field.
Its true sonicexcellence and portable, rugged design make it the perfectchoice for electronic news gathering (ENG), electronic field
production (EFP), and feature film production.
Please be sure you have read, understand, and agree to allterms stated in the LICENSE AGREEMENT on page 9 of thismanual and on your warranty registration card.
APPLICATIONS
•
•
•
•
•

Location Recording (Dialogue and Music)
Digital Recording and Playback
M/S Stereo Recording and Monitoring
Broadcast Remotes
Desktop Mixing for Video Post Production

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INPUTSA.

Input Mode (MIC/LINE)
1.
The PSC M4 A+ can accommodate microphone level
inputs as well as line level inputs (-10 to +4dBu).
The M4 is compatible with all forms of consumer andprofessional audio equipment.
The MIC/LINE switches
are located on the bottom panel of the M4.

B.

Balanced Inputs
1.
The PSC M4 A+ provides four input channels
utilizing female XLR connectors.
The studio grade
input circuitry is electronically balanced.
The XLR
connectors are wired as follows:
pin 1 shielded
ground, pin 2 audio high, and pin 3 audio low.
Balanced wiring enables longer cable runs without theworry of excessive noise due to nearby electromagnetic
and radio frequency interference.
Either pin 2 or 3
may be tied to ground to unbalance the inputs of the M4
A+.
Note: The AES standard for unbalancing an XLR
connector is to tie pin 3 to ground.

C.

Dynamic, 48V PH and 12V "T" Microphone Powering
Channel microphone powering switches are located on thebottom panel of the M4 A+.
Each channel isindividually switchable between dynamic, 48V phantom
and 12V "T" powering.
1.
In the dynamic position (DYN), the mixer provides
no form of microphone powering. Inputs set to dynamicon the M4 A+ may be used with dynamic microphones orline level outputs from wireless receivers or taperecorders.
2.
In the 48V phantom position (48PH) the mixer
provides 48 volts DC to power 48PH microphones orsimplex powered microphones with a range of 9 to 52
volts or 12 to 52 volts. Pin 1 is shielded to ground
while pins 2 and 3 carry 48 volts dc.
The term"phantom" is derived from the fact that there is no
voltagepotential
developed
acrossaadynamic
microphone transducer that would interfere with its
operation.
However, most portable wireless receivers
will not operate with 48PH turned on.
We strongly
recommend setting inputs to dynamic for use withwireless systems.

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3.
In the 12V Tonador position (12T), the mixer
provides 12 volts DC to power "T" or "AB" microphones.
With standard 12 "T" powering, pin 1 is shielded to
ground while pin 2 is connected to the positive supply
voltage and pin 3 to the negative supply voltage. 12T
must not be used when operating anything other than "T"
or "AB" microphones.
D.

Pre-Amplifier Attenuation
1.
Each channel has switchable gain (0dB, -10dB, 20dB) to assist in preventing pre-amplifier overload.
The -10dB and -20dB settings can be used to record highlevel sounds or when using very sensitive microphones.
The pre-amplifier attenuator switches are located on
the bottom panel of the M4 A+.
The -10dB setting isnormally used when operating condenser (powered)microphones.

E.

Low Cut Filter
1.
Each channel has a low cut (high pass) filter.
This filter will attenuate all frequencies below apreset frequency at a rate of 12dB per octave.
When
set at 20Hz, frequencies below 20Hz are
effectively
rolled off with the mixer operating at full frequency
response. Optional low cut filter settings of 100Hz
and 140Hz will roll off the frequencies below those
figures at rate of 12db per octave (-3db level at 100Hz
and 140Hz respectively).
Low cut filtering isimportant in location recording where wind noise cancause pre-amplifier overload.
This effect can be
minimized by switching the low cut filter setting toeither a 100Hz or 140Hz cutoff.
The low cut filter
switches are located on the front of the M4 A+.

F.

Channel Amplifier Gain
1.
In order to limit noise and increase headroom, thechannel fader controls are located in the feedback pathof the pre-amplifiers.
This allows the operator todecrease pre-amplifier gain rather than just channel
output
level
when
an
overload
situation
occursresulting in increased headroom and lower chance of
signal clipping (severe distortion).

G.

Channel Assignment
1.
Channel assignment enables the assignment of a
input channel signal into the left or right mix busses.

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Individual channel assignment is accomplished with athree way channel assignment switch to left, center(left and right), or right buss.
This switch islocated on the right side panel of the mixer.
H.

Slate Microphone1.
The slate microphone can be activated with themomentary pushbutton switch located in the upper righthand corner of the front panel. The operating level ofthe slate microphone is adjustable via a screwdriveradjustable trim pot located on the right side of themixer.

I.

Protection
1.
The PSC M4 A+ inputs, outputs and powering areextensively overload protected to prevent mixer failurein the event that an incompatible signal (voltage) isconnected to the M4 A+ (i.e., feeding dc into an audio
input).
2.
Each input and output on the M4 A+ is EMI (RF)filtered to help eliminate the effects of interference
from radio microphones, walkie talkies, business band
radios, television and radio transmitters.
These
filters will remove stray frequencies in the radio band
while allowing audio frequencies to pass through. Thisisanespecially
importantfeatureforfield
production.

STEREO/MS
A.

Stereo and Mid/Side Recording
1.
The PSC M4 A+ mixer can be used to make highquality XY and MS stereo recordings. When used in thismode, BOTH mixer mode switches must be set to theganged position.
Channels one and two are ganged
together when used in this manner.
The channel one
fader becomes the master level control for both inputs
and the channel two fader is a balance control (+/9dB).
The balance control affords either level
matching of an XY pair or stereo imaging of an MS
stereo recording.

OUTPUTSA.

Balanced Outputs

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1.
The PSC M4 A+ stereo outputs utilize two male XLR
connectors.
The
outputsarelowimpedance,electronically balanced and capable of driving +4dBm
lines with more than 16dB of headroom. The advantagesof balanced lines have been stated previously in thisoperation manual (see Balanced Inputs). The outputs of
the M4 A+ may be unbalanced by tying either pin 2 or 3
to ground.
The AES standard for unbalancing an XLR
connector is to tie pin 3 to ground.
Addiontionaly,
the outputs may be switched to microphone level if sodesired.
2.
A stereo microphone level unbalanced output isavailable via a stereo mini female jack located on theright side of the mixer. This is typically used to feed
audio to transcription recorders.
3.
Output limiters, located on the right side of themixer, may be switched on
or off. They are factory
calibrated to activate at approximately +3 on the V.U.
meters. Compression is a reasonable 2.4 to 1.
B.

Accessory Connector
1.
The accessory connector, located on the left sideof the M4 A+, is of particular importance to portablevideo camera operators. A quick-release Hirose(tm) 12
pin
connector
providesbalanced
outputs,
useradjustable balanced tape returns and the ability topower the M4 A+ externally. To take full advantage ofthis feature, optional PSC snake cables are available
in many configurations.
These snake cables provide aconvenient single connector hook up to the PSC M4 A+
and are available in standard or quick disconnect (nearthe camera) configurations.

MONITORA.

Headphone Monitor Output
1.
The 1/4" stereo headphone amplifier output canaccommodate 25-600 ohm headphones. A volume control islocated on the right side of the mixer.
2.
Monitoring is switchable between left, mono,right, stereo and M/S. Headphone monitor switches arelocated on the bottom panel and front panel below themaster fader.
Monitoring is also MixBus/TapeReturnselectable. The Mix/Tape switch is on the right sideof the M4 A+.

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TAPE RETURNSA.

Tape Return Gain
1.
The tape return right and left channel gain
adjustments are accessible on the bottom panel. The M4
A+ will accept either balanced or unbalanced signals
and will operate over a wide range of external device
output levels. Input impedance of the tape returns is
100k ohms balanced and 50k ohms unbalanced.
This
impedance was chosen in order to accommodate any
external device without signal loading.
Tape returns
are accessible via the accessory 12 pin connector on
the left side of the mixer.

METERSA.

V.U. Meters
1.
The two V.U. meters are Sifam(tm) taunt band
units.
These are rear lit via a user operated timed
circuit. Illuminating the V.U. meters is accomplishedwith a momentary lamp switch located on the front panelof the M4 A+ just to the right of the V.U. meters. The
lamps are automatically held on for approximately 12
seconds after which they return to off.
2.
A momentary battery check switch, located on theleft side of the M4 A+, will display a new set ofbatteries at 100% on the right V.U. meter.
Consideralkaline batteries "dead" at 50%.

B.

PPM Meters
The two PPM meters are SIFAM(tm) taunt band units. The
muax PPM version also contains an additional circuitboard to provide the required PPM ballistics.
Theelectrodes utilized for this function were custom
designed by PSC, and meet all applicable BBC and EBU

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standards.
Additionally, PSC's exclusive circuitry
consumes very little power when compared to competiting
designs.

POWERING
A.

Internal Battery Powering
1.
The M4 A+ mixer is powered internally by eight"AA"batteries.
Alkaline
type
batteries
arerecommended and will provide 20-30 hours (V.U. Meters)of operation under normal use.
The PPM version will
normally provide 18-25 hours of operation under normal
use. Batteries should be removed when the mixer will
not be in operation for extended periods of time.
2.
A low battery level LED is located on the front
panel of the M4 A+. It "blinks" whenever the mixer isturned on. It blinks once every six seconds in order
to conserve power.
It illuminates steadily withapproximately one hour of battery life remaining.
3.
The battery compartment is located on the rightside of the mixer.
Batteries are replaced via thethumb screw attached door.
Please note the battery diagram on the bottom of the M4
A+ to ensure proper polarity. If the batteries are
inadvertantly installed backwards, no damage will
result, the mixer will simply not operate.

B.

External DC Powering
1.
The PSC M4 A+ can be powered externally from 6 to
24Vdc. The low voltage indicator will stay lit below
7.5 volts, while the mixer is in operation.
Powerconsumption is less than 0.8 Watts (aprox 65mA @12Vdc)
with no microphones powered.
External powering isavailable through the 12 pin accessory jack located on
the left side panel of the mixer. An optional PSC M4
A+ wall pack DC power supply is available. Additional
Hirose inline connectors (Part # HR10A-10P-12P) arealso available.
2.
External powering can also be accomplished throughthe use of the BP-90-type chassis battery connector
located on the right side of the mixer.
Wiring is8

consistent with the common Sony camcorder battery
polarity(Outside = + voltage, Center = - voltage).
3.
WARNING!:
DO NOT EXCEED 25V DC!
Any voltage
above this point will damage the mixer and void the PSC
M4 A+ warranty. The mixer is internally equipped withawarranty-validating"tell-tale"componenttodetermine extreme operating voltages.
M4 CONSTRUCTION
A.

Chassis1.
The M4 A+'s extremely rugged, yet lightweightchassis is formed from high grade aircraft aluminum.
All chassis parts are chem film-plated to resist
corrosion.
The
exterior
finishconsistsofelectrostatically applied, baked-on black matte powder
coat polymer.
2.
The lettering used on the M4 A+ is mil-spec longwearing epoxy based inks that are baked on for adurable finish.

B.

Environmental Operation
1.
The PSC M4 A+ has been engineered so that it willremain functional under the most adverse environmental
conditions. The M4 A+ was designed to be operated over
the temperature range of -20C to +70C (-4F to +158F).
Battery life will be substantially reduced at the lower
temperature extremes.
We recommend Eveready(tm) AA
lithium
batteries(model#L91)
forextremelowtemperature operation.

INTERFACING
If you plan to transmit the outputs of the M4 A+ mixer via a
LectrosonicsTM wireless systems, you should plan to order apair of M4 output to Lectrosonics input cables from yourlocal dealer (PSC inventory number FPSC1125). These cables
are optimized to prevent any RF interference from affecting
the audio integrity of the M4 A+ stereo outputs.
WARRANTY AND NON-WARRANTY SERVICE
Complete details of the PSC M4 A+ warranty are given on theenclosed blue warranty registration card.
If you did notreceive one please contact your local dealer or call us
directly.

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The PSC M4 A+ mixer has been designed to provide you withyears of trouble free service.
However, in the unlikely
event that your PSC M4 A+ mixer requires service, pleasecontact your local dealer or Professional Sound Corporation
during normal business hours.
Please return your PSC M4
A+mixer in its original shipping box, freight prepaid, to:Professional Sound Corporation
24932 Avenue Kearny #8
Valencia, CA 91355
U.S.A.
We reserve the right to inspect products which may besubject of any warranty claim before repair or replacement
is carried out.
PSC M4 A+ mixers repaired under warranty will be returned
within
30days
freight
paidbyProfessional
Sound
Corporation.
Repairs that do not meet the terms of thewarranty will be repaired and returned within 30 days C.O.D.
with billing for labor, materials, freight and insurance.

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LICENSE AGREEMENTThe Professional Sound Corporation M4 A+ Audio Mixer islicensed to registered PSC Dealers and to end users whopurchase the M4 A+ Mixer.
Professional Sound Corporationagrees to license each M4 A+ Mixer sold to a registered PSC
Dealer or end user under the protection of the industrial
trade secrets laws of the State of California and the UnitedStates of America.
Under the terms of this agreement thelicense is for the use of the M4 A+ Mixer for fifty (50)years. Ownership of all technology employed in the PSC M4
A+ remains with Professional Sound Corporation.
Professional Sound Corporation retains proprietary rights toall design documentation, manufacturing processes, and otherdata developed or created by Professional Sound Corporationin designing the M4 A+ Mixer.
This product is licensed by Professional Sound Corporation
for the following registered Dealer and end user purposes:
PERMITTED USES (YOU MAY):• Electronic News Gathering (ENG) sound mixing.
• Video and Film production and post production
mixing.
• Video and film Documentary sound mixing.
• Any other similar sound mixing applications.

sound

PROHIBITED USES (YOU MAY NOT):• Copying or reverse engineering all or any portion of the
PSC M4 A+ Mixer.
• Alter or Modify the PSC M4 A+ Mixer.
This license and the right to use the Professional Sound
Corporation M4 A+ Mixer will automatically terminate by
failure to comply with any provision of this license
agreement.
Professional Sound Corporation retains allrights not expressly granted.
Nothing in this agreement
constitutes a waiver of Professional Sound Corporation's
rights under United States Copyright trade secret laws or
any Federal or State laws.
This agreement becomes effective for each Mixer when the
License Seal is broken
by the registered Dealer or end
user.
License may be transferred to subsequent owners if
notification in writing is given to Professional Sound
Corporation. It is the sole responsibility of the end user

11

to transfer this license upon transferring the ownership ofthe Mixer to a third party.

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SPECIFICATIONS

Freq. Response:

20Hz to 20KHz +-0.5dB.

Distortion:

20Hz to 20KHz <=0.08%.

Crosstalk:

20Hz to 20KHz >= 70dB.

Noise Figure:

20Hz to 20KHz -130dBu.

Microphone Powering:48 PH per DIN specification.
12 T per DIN specification.

Low Cut Filter:

20, 100, 140Hz at 12dB/octave.

Oscillator:

400Hz sine wave at O V.U. via momentary
pushbutton switch located on the right side of
the mixer.

Global Gain:

80 dB at "0" detent on the master fader.
86 db at maximum on the master fader.

Source Input
Impedences:

150 ohms rated.

Line Output
Load Impedance:

600 ohms rated.

Tape Return Impedance:

100k ohms balanced, 50k ohms unbalanced.

Headphone Load
Impedance:

25-600 Ohms.

Voltage Rails:+/-16Vdc.

Internal Power:

Eight "AA" alkaline batteries providing 20-30
hours of operation under normal operating
conditions.

External Power:

9 to 24Vdc via 12 pin Hirose connector or the
BP-90 jack. Power consumption <= 0.8 Watts withno microphones powered. WARNING: Do not exceed
25Vdc.

Temperature Range:-20 to +70C (-4 to +158F).
batteries.

Dimensions:

285mm H x 180 mm W x 46 mm D (11.25" x 7.125" x1.875")Net Weight:

1.59Kg (3.5 lbs.)

Specifications subject to change without notice.

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Less the effects on