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INSTALLATION:
CONNECTION BETWEEN COMPONENTS
For balanced-line connection use two-conductor,
shielded, low-capacity cable.
For unbalanced (high-
impedance) connection, use single conductor, shielded,
low-capacity cable.
p . E L ! - m
p ; 3 E G ! m
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\1----
--/
MICROPHONE
M I C .
INPUT
MICROPHONE
MIC. INPUT
LOW IMPEDANCE
HIOH
IMPEDANCE
(BALANCED LINE)
M I C R O P H O N E INPUT
PLUG
CONNECTIONS
SHIELD
2
MIC. OUTPUT
M I C .
OUTPUT
L O W IMPEDANCE
HIGH IMPEDANCE
(BALANCED LINE)
MICROPHONE OUTPUT
P L U G
CONNECTIONS
MICROPHONE CONNECTIONS
-
FIGURE B
INPUT CONNECTIONS
Microphones: A maximum of four low or high-imped-
ance dynamic, ribbon, or capacitor (condenser) micro-
phones may be connected to receptacles marked Mic.
1, Mic. 2, Mic. 3 and Mic. 4. The inputs are designed
for low-impedance microphones with 25 to 600 ohms
impedance or high-impedance microphones, as selec-
ted by a slide switch above the input receptacle. The
unit is not recommended for use with crystal or ce-
ramic microphones. The input receptacles, Mic. 1,
Mic. 2, Mic. 3 and Mic. 4 are female professional
three-pin audio connectors* (mate, Shure Part 95A407).
See Figure B for low-and high-impedance connections
to receptacle.
(NOTE: Some capacitor (condenser) microphones
produce very high output signals which may overload
the input of a mixer. A Shure Model A15A Microphone
Attenuator placed between the microphone and the
mixer input will eliminate this problem.)
Aux. Input: The left channel (L) and right channel (R)
phono jacks marked Aux. Input on the rear panel will
accept the output from a high-impedance, high-level
source such as a tape recorder, AM-FM tuner, or
output from a phono cartridge preamplifier, such as the
Shure Model M64 or A68P (2 Model A68P's required
for Stereo). One or more Shure M68 Series Microphone
Mixers may be connected to these jacks to add addi-
tional microphone inputs.
Mix Bus: The left channel (L) and right channel (R)
phono jacks marked Mix Bus on the rear panel are
used when paralleling M688 units to increase the
number of input channels. Use a phono pin plug
jumper cable between each L Mix Bus jack, and an-
other between each R Mix Bus jack.
OUTPUT CONNECTIONS
Auxiliary Output: The left channel (L) and right chan-
nel (R) phono jacks marked Auxiliary Output are high-
impedance high-level outputs designed primarily to
feed power amplifiers requiring 0.1 to 2 volts, or the
auxiliary or tuner inputs of an amplifier or tape re-
corder.
Mono Mic. Output: The receptacle marked Mono Mic.
Output has a low- or high-impedance output selected
* Designed to mate with Cannon XL series, Switchcraft A3
(Q.G.) series, or equivalent connector.
by the switch above the receptacle. This output is the
"Mixed"
(L
+
R) monaural output of all the input
sources and is designed to work into a 25 to 600 ohm
mic. input, or into a high-impedance amplifier or tape
recorder microphone input. The receptacle is a male
professional three-pin audio connector.'
See Figure
B for output receptacle connections.
30 V.D.C.:
These rear panel jacks provide 27 Vdc
open circuit (21 Vdc at 5 mA max.) for accessories.
An external battery pack, such as the Shure Model
A67B or A68B, or an external 26 to 30 Vdc source
may also be used to power the M688 via these jacks.
OPERATION
Power: Connect the three conductor power line cord
to a 120 volt, 50/60 Hertz ac power outlet.
The
power ON-OFF switch is on the front panel. A neon
pilot lamp indicates that the ac power is on. (This
lamp does not light when the unit is battery operated).
If battery operation is desired, do not connect line
cord. The ON-OFF switch also controls battery input
power.
Volume Controls:
The Master volume control and the
individual volume controls for each of the five channels
are identified on the front panel. Both the Aux. volume
control and the Master volume control are clutched
dual concentric controls. The left channel (L) control
is the large outer knob. The right channel (R) control
is the smaller inner knob. The relative setting of the
left and right controls may be changed by restraining
one knob and moving the other. Above the Master
volume control is a Mono-Stereo switch used for se-
lecting either monaural or stereo output at the Auxiliary
Output L and R jacks on rear of chassis. Individual
channel volume controls not being used should be
kept at minimum setting (fully counterclockwise).
Mic. 4 Pan Control:
The Mic. 4 Pan Control on the
front panel is used for adjusting the apparent location
of the Mic. 4 Signal to either left or right positions or
anywhere between. When the Mic. 4 Pan Control is
in the maximum left position, program material on
Mic. 4 appears only at the Auxiliary Output left channel
(L); likewise, when the Mic. 4 Pan Control is in the
maximum Right position, the program material appears
only at the Auxiliary Output right channel (R). When
the Mic. 4 Pan Control is centered between Left and
Right, the Mic. 4 program material appears equally on
both left (L) and right (R) Auxiliary Output phono jacks.
The program material on Mic. 4 appears at the Mono
Mic. Output no matter where the Pan Control is set.
In making a stereo recording or with a stereo sound
reinforcement system, it may be desirable to place the
vocalist on Mic. 4 so the voice may be "centered"
between the left (L) and right (R) stereo channels
containing the orchestra.
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.
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