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Grounding
If there should be objectionable hum, connect the
metal chassis of the mixer to a good ground such as
a 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:
A maximum of four high-impedance
dynamic, ribbon, or condenser microphones may be
connected to the standard
Y4"
phone jacks marked
MIC. 1, MIC. 2, MIC. 3, MIC. 4. The microphone inputs
may be converted for use with low-impedance micro-
phones by utilizing accessory plug-in transformers
Model A95 Series. The unit is not recommended for
use with crystal or ceramic microphones.
NOTE: Some condenser microphones produce very
high output signals which may overload the input of
a mixer.
Auxiliary: The phono jack on the rear of the panel
marked AUX. INPUT will accept output from a high-
impedance, high-level source such as a tape recorder,
AM-FM tuner, or output from the Model A68P Phono
Preamplifier (accessory). The Model A68M Microphone
Preamplifier (accessory) may be connected to this
jack to provide a fifth microphone input.
OUTPUT CONNECTIONS
Low lmpedance Microphone: The receptacle marked
LO IMP. MIC. OUTPUT is a low-impedance micro-
phone level output. 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 low-imped-
ance amplifier or tape recorder microphone input. The
receptacle is a professional three-pin audio connector
(male).? See Figure B for output receptacle connec-
tions.
SHIELD
SLEEVE
-----
TIP
j
\ - - - - -
2
._-_--
d
MIC.
OUTPUT
MIC. OUTPUT
HIGH IMPEDANCE
LOW IMPEDANCE
(BALANCED
LINE)
Microphone Output Connections
FIGURE B
High lmpedance Microphone: The phone jack marked
HI IMP. MIC. OUTPUT is a high-impedance microphone
level output. This output is, also, the "mixed" output
of all sources, designed to work into
a
high-impedance
amplifier or tape recorder microphone input. See
Figure B for output jack connections.
NOTE: The high- and low-impedance microphone out-
puts may be used simultaneously.
Auxiliary: The phono jack marked AUX. OUTPUT is
a high-impedance high-level output designed primarily
to feed a power amplifier requiring 0.5 to 2 volts or
the auxiliary or tuner input to an amplifier or tape
recorder. This output will also drive the input of the
Model M63 Audio Master.
Accessory 28-volt dc: This rear panel jack marked
ACCESSORY 28 V.D.C. provides 28 volts dc for ac-
cessories such as the Model A68P Phono Preamplifier,
Model A68M Microphone Preamplifier or M62V Level-
Loc. The jack is also used as the power input when
using the Model A67B Battery Power Supply (acces-
sory) for battery operation of the M68P Mixer.
?
Designed to mate with Cannon XL series, Switchcraft A3
(Q.G.) series or equivalent connector. [Shure part 95A548
(female)].
OPERATION
Power: Connect the Microphone Mixer power line cord
to the proper ac power outlet. See Operating Voltage
under Specifications. The M68P has a three-conductor
cable with a three prong plug.
Volume Controls: The MASTER gain control and the
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 (fully clockwise) and the MASTER gain
control adjusted to required output. Individual channel
gain controls not being used should be kept at mini-
mum gain (fully counterclockwise).
Identifying Controls: Pressure sensitive adhesive labels
are supplied with the Mixers as a means of identifying
each control and recording that controls position when
optimum results have been obtained. The labels are
easily removed when their use is no longer required.
CONNECTING TWO UNITS TOGETHER
Two M68P Mixers may be combined to give a total
of eight microphone channels plus an auxiliary input.
A. Connect the AUX. OUTPUT of Unit 1 to the AUX.
INPUT of Unit 2.
6.
Connect microphones to mixers and set each mi-
crophone input control to # O position.
C. Take the output signal for recorder or P.A. amplifier
from the appropriate output jack on Unit 2.
D. Set MASTER control on Unit 1 to position #4.
E. Set AUX. control on Unit 2 to position # l o .
F. The MASTER control on Unit 2 is now the MASTER
for all inputs.
G. Advance MASTER control (Unit 2) to about # 5 po-
sition and adjust individual microphone controls for
proper level. If overall gain is too low or too high
the MASTER control (Unit 2) may be adjusted.
H. If an input to the auxiliary channel is needed, such
as for a tape recorder or tuner, use AUX. INPUT on
Unit 1. Use AUX. control on Unit 1 for level adjust-
ment of the auxiliary source. The master gain con-
trol for the entire system is the MASTER control
on Unit 2.
The Model A68S Stacking Kit includes stacking
brackets for attaching the two mixers firmly together
plus the required inter-connecting cable. The cable
only, is available separately under the Model A68SC.
GUARANTEE
This Shure product is guaranteed in normal use to
be free from electrical and mechanical defects for a
period of one year from the date of purchase. Please
retain proof of purchase date. This guarantee includes
all parts and labor.
SHIPPING INSTRUCTIONS
Carefully repack the unit and return it prepaid to
the factory. If outside the United States, return the unit
to your dealer or Authorized Shure Service Center for
repair. The unit will be returned to you prepaid.
OPTIONAL ACCESSORIES
Battery Power Supply
. . . . . . . . .
.Model A67B
Output Cable Kit
. . . . . . . . . . . . . .
.Model A68C
Locking Panel
. . . . . . . . . . . . . . . .
.Model A68L
Phono Preamp
. . . . . . . . . . . . . . . .
.hlodel A68P
Rack Panel Kit
. . . . . . . . . . . . . . . .
.Model A68R
Stacking Kit
. . . . . . . . . . . . . . . . . .
.Model A68S
. . . . . . . . .
Interconnecting Cable
.Model A68SC
Attache Case
. . . . . . . . . . . . . . . . .
.Model AC60
Handle/Tilt Stand
. . . . . . . . . . . . .
.Model A67H
Line Matching Transformer
. . . . .
.Model A95 Series
Microphone Preamplifier
. . . . . . .
.Model A68M
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