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222 HARTREY AVE.. EVANSTON. IL. 60204
u.s.A.
DATA
MODEL M688 AND M688E
SHEET
STEREO MICROPHONE
Q A R E A C O O E ~ ~ ~ / ~ ~ E - 9 0 0 0
.
CABLE: SHUREMICRO
MIXERS
GENERAL:
The Shure Model M688 is a completely transistor-
ized, portable Stereo Microphone Mixer for use with
sound reinforcement systems and tape recorders.
The Model M688E Stereo Microphone Mixer is simi-
lar to Model M688 except that it is designed to be
connected to a 120 + l o %
or 240 & l o % volt ac
power line, as selected by a switch under the chassis.
Features include:
Stereo High lmpedance Auxiliary Outputs.
Mono Microphone Level Output for mixed (L
+
R) monaural output.
Four Microphone Inputs, low impedance (bal-
anced) or high impedance (unbalanced).
Stereo, High Level Auxiliary Inputs suitable for
tape recorder, tuner, or the output of a stereo
magnetic Phono Preamp such as the Shure
Model M64.
Individual Volume Controls for each input.
A Stereo Master volume control to simu-ltaneous-
ly adjust level of all inputs.
A Mono-Stereo switch.
Left-Right switches for Mics. 1, 2 and 3.
A Pan Control used for adjusting the apparent
location of the Mic. 4 input to either left channel
or right channel position or anywhere between.
Mix Bus jacks for paralleling two or more M688
units.
Dc Power jacks to supply 27 Vdc for use with
accessories or to allow powering the M688 from
an external source, such as a Shure Model A67B
Battery Power Supply.
Underwriters' Laboratories, Inc., listed, and listed
by C.S.A. as certified (M688 only).
Dimensions:
See Figure A
5.5
mm
17/32
IN)
OVERALL DIMENSIONS
-
FIGURE A
Net Weight:
2.27 kg (5 Ib)
SPECIFICATIONS
Gain:
At 1000 Hz (Stereo Position)
OUTPUT
Low
High
Aux.
INPUT
~-
Mix
Bus
Imp. Mic.
Imp. Mic.
(High Imp.)
Low Imp. Mic.
+
13.5 dB
+
1.5 dB
+25.5 dB
+59.0 dB
High Imp. Mic.
-
9.5 dB
-
21.5 dB
+
2.5 dB
+
36.0 dB
Mix Bus
-
-23.0dB
+
l.OdB
+34.5dB
AUX.
-31.0 dB
-43.0 dB
-19.0 dB
+14.5 dB
Frequency Response:
Flat -c3 dB from 40 Hz to 20,000 Hz
Maximum Output Hum and Noise:
300-20.000 Hz
20-20,000
Hz
(Aux. Output, All Controls Min.) -80 dBV
-68 dBV
(Aux. Output, All Controls Max.) -60 dBV
-50 dBV
lnput Impedance:
Microphone inputs suitable for high- or low-impedance
dynamic, ribbon, or capacitor (condenser) microphones.
Auxiliary input
-
50,000 ohms. Mix Bus
-
3,300 ohms.
Recommended Load Impedance:
Low lmpedance
Microphone Output
....................
25 to 600 ohms
High lmpedance
Microphone Output
....................
20,000 ohms or greater
Auxiliary High lmpedance Output 50,000 ohms or greater
...........................................
Mix Bus
2,700 ohms
or
greater
Distortion:
Less than 1 % Total Harmonic Distortion when Low Im-
pedance Microphone Output is at 5 mV level, High
lmpedance Microphone Output is at 70 mV level, and
Aux. Output is at 2.0 volt level.
lnput Clipping Level:
Minimum Clipping Level
Low Impedance Microphone Input ..........
25 mV
High Impedance Microphone Input ........
350 mV
Mix Bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6 5 0 m V
Output Clipping Level:
O u t p u t
Low Imp. Mic.
High Imp. Mic.
Aux.
Stereo
Mono
Stereo
Mono
Minimum Clipping Level
7 mV
14 mV
110 mV
220 mV
Stereo
6.6V
Mono
5.7V
Phase:
The Mono Mic. Output is i n phase with all microphone
inputs. The Mix Bus is out of phase with pin 3 of the
microphone inputs. The Auxiliary Output is out of phase
with pin 3 of the microphone inputs. The Auxiliary Output
is in phase with the Aux. lnput and the Mix Bus.
Operating Voltage:
MODEL M688
Ac Operation:
120 volts, + - l o % at 50 to 60 Hz
Dc Operation:
30 volts, 7.5 mA
MODEL M688E
Ac Operation:
120 or 240 volts, -t-10% at 50 to 60 Hz
Dc Operation:
30 volts, 7.5 mA
The Model M688E is supplied with a three-conductor
power-line cord, but no plug. The power-line cord plug
should be installed by a qualified person. The brown lead
should be connected to the "live" or "hot" terminal of the
plug, and the blue lead to the neutral terminal of the plug.
The green/yellow lead is the grounding conductor and
should be connected to the ground or earth terminal of
the plug.
Copyright
1 9 7 1 ,
Shure Brothers Incorporated
27A1009 (01)
Printed
i n
U.S.A.
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