Grounding
If
there should be objectionable hum, connect the
metalchassisof the mixer toagood groundsuchas the
metal frame of a wall outlet, or a water or steam pipe.
This is normally accomplished automatically through
the ground wire of the power cord.
INPUT CONNECTIONS
Microphones
Up tofour low-or high-impedancedynamic, ribbon,or
condenser microphones can be connected to recep-
tacles marked Mic 1, Mic 2, Mic 3, Mic
4.
The inputsare
designed for low-impedance microphones with 25 to
250 ohms impedance or high-impedancemicrophones.
Both low-impedance or high-impedance microphones
can be used simultaneously. The unit is not recom-
mended for use with crystal or ceramic microphones.
The impedance is selected by a slide switch above the
input receptacle.The input receptaclesare professional
audio connectors (three-pin on the M68 and three-
socket on the M68FC)*.See Figure2 for low-and high-
impedance connections to receptacle.
PICTORIALLY
-
PINS I AND
2.
INPUTS ONLY,
REVERSED FOR MODEL M68FC AND M68FCE
,
C:7%IEL.Qq
------
.,-
-
-
-
-
2'
MICROPHONE MIXER INPUT MICROPHONE MIXER INPUT
LOW IMPEDANCE HIGH IMPEDANCE
(BALANCED LINE)
MICROPHONE INPUT CONNECTIONS
SHIELD SHIELD
c----;?
m-------;TJ
xu-----
MIC
OUTPUT----- MIC.
OUTPUT
LOW IMPEDANCE HIGH IMPEDANCE
(BALANCED LINE)
MICROPHONE OUTPUT PLUG CONNECTIONS
MICROPHONECONNECTIONS
FIGURE
2
NOTE:
Some condenser microphones produce very
highoutput signals which may overloadthe mixer input.
A Shure Model A15AS Microphone Attenuator placed
between the microphone and the mixer input will
eliminate this problem.
Auxiliary
The phonojack on the rear of the panel markedAux
lnput will accept output from a high-impedance, high-
level source such as a tape recorder, am-fm tuner, or
phono cartridge preamplifier. The Model A68M
MicrophonePreamplifier can be connected to this jack
to provide a fifth microphone input.
OUTPUT CONNECTIONS
Microphone
The receptacle marked Mic Output is a dual-
impedance output selected by the switch above the
receptacle. This output is the "mixed" output of all the
input sources and is designed to work into a 25 to
600-ohm microphone line or into a high-impedance
amplifier or tape recorder microphoneinput.The recep-
tacle is a professional three-pinaudio connector*. See
Figure2 for output receptacle connections.
Auxiliary
The phono jack marked Aux High Level Output is a
high-impedancehigh-leveloutput designed primarily to
feed a power amplifier requiring 0.5 to 2 volts, or the
auxiliary or tuner input toan amplifier or tape recorder.
Accessory 28-volt DC
The rear paneljack, markedAccessory 28 V.D.C. pro-
vides 28 Vdc open circuit (20Vdc at 5 mA max.) for ac-
cessories such as the Model A68M Microphone
Preamplifier. The jack is also used as a power input
when using the Model A67B Battery Supply.
CAUTION:
The 28 Vdc input circuit of the M68 is not
fused. An external 28 Vdc source should be provided
with a 0.125A, 250V in-linefuse as a safety precaution.
OPERATION
Power
Connect the mixer power cord to the proper ac power
outlet (see Operating Voltage under Specifications).
'Designed to
mate
with
Cannon
XL
series,
Switchcraft
A3
(Q.G.)
series
or
equivalent
connector.
Volume Controls
The Master gain control and individual gain controls
for each of the five channels are identified on the front
panel. The individual gain controls should generally be
set near maximum(fullyclockwise)andthe Mastergain
control adjusted to requiredoutput. Individual channel
gain controls not being used should be kept at
minimum gain (fully counterclockwise).
CONNECTING TWO UNITS
Two M68 mixers may be combined to give a total of
eight microphone channels plus an auxiliary input as
follows.
1. ConnectAux HighLevelOutput of Unit 1toAux lnput
of Unit 2.
2. Connect microphones to mixers and set each
microphoneinput control to
"O".
3. Take output signal for recorder of
PA
amplifier from
appropriate output jack on Unit 2.
4.
Set Mastercontrol on Unit 1 to
4.
5. Set Aux control on Unit 2 to 10.
6. Mastercontrol on Unit 2 is now Masterfor all inputs.
7.
Advance Mastercontrol(Unit2) toabout5andadjust
individual microphone controls for proper level. If
overall gain is too low or too high, Master control
(Unit 2) can be adjusted.
8. If input to auxiliary channel is needed, such as for
tape recorder or tuner, use Aux lnput on Unit
1.
Use
Aux control on Unit 1 for level adjustment of Aux
source. Master gain control for entire system is
Mastercontrol on Unit 2.
GUARANTEE
This Shure product isguaranteed innormaluseto be
free from electrical and mechanicaldefects for a period
of one year from date of purchase. Please retain proof
of purchasedate. This guarantee includes all parts and
labor. This guarantee is in lieu of any and all other
guarantees or warranties,express or implied, and there
shall be no recovery for any consequential or incidental
damages.
SHIPPING INSTRUCTIONS
Carefullyrepackthe unit, haveit insured,andreturnit
prepaidto: Shure Brothers Incorporated
Attention: Service Department
222 HartreyAvenue
Evanston, Illinois60204
If
outside the United States, return the unit to your
dealer or Authorized Shure Service Center for repair.
The unit will be returnedto you prepaid.
OPTIONAL ACCESSORIES
BatteryPowerSupply
..................
ModelA67B
LockingPanel
........................
ModelA68L
RackPanelKit
...................
ModelsA68R, -BL
MicrophonePreamplifier
...............
ModelA68M
MicrophoneAttenuator
...............
ModelA15AS
