Page 1
CONTROLS, CONNECTIONS AND OPERATION
WARNING
To reduce the risk of fire or electric shock, do
not expose this appliance to rain or extreme
moisture.
1
INPUTS The two high impedance inputs (phono jacks)
marked HlGH LEVEL INPUTS are designed to accept
high level signals from a microphone mixer (such as
the Shure M68, etc.), tape recorder, AM-FM tuner, or
output from a Shure Model
A68P Phonograph Pre-
amplifier (accessory).
To use with the Shure M68 Microphone Mixer
series, connect the AUX. HlGH LEVEL OUTPUT on
the mixer to the input of the M63 with a shielded
cable having a phono plug on each end. Set the
MASTER volume control on the mixer to approximately
6 and use the VOLUME control on the M63 to adjust
the overall level.
Although not specifically designed for use with the
Shure M67, it may be used in conjunction with the
M67 in the following manner: connect a shielded
single conductor cable with a
%" phone plug on one
end and a phono plug on the other from the head-
phone output of the M67 to the M63 input. To obtain
good volume control action from the M63, install a
180-ohm resistor from tip to sleeve in the phone plug
and use the M63 volume control to adjust the output
to the desired level.
OUTPUTS
Microphone
The receptacle marked MICROPHONE LEVEL OUT-
PUT is a dual impedance output selected by the
switch above the receptacle. This output is designed
to work into a balanced 25- to 250-ohm input, or, with
the MICROPHONE IMPEDANCE selector switch in the
Hi position, into an unbalanced high impedance mi-
crophone input on an amplifier or tape recorder. The
receptacle is a professional three-pin audio con-
nector designed to mate with Cannon XL series,
Switchcraft A3 (Q.G.) series or equivalent connector.
See Figure
1 for output receptacle connections.
WELDD_ 10 . - - SHIELD - - - - - !T"- e3 ; \------A/ I ,-------I MIC. OUTPUT MIC. OUTPUT
HlGH IMPEDANCE LOW IMPEDANCE
(BALANCED LINE)
MICROPHONE OUTPUT PLUG CONNECTION
FIGURE 1
Line
The line output (binding posts) is on the rear panel
and is designated 600 OHM BALANCED
LINE OUT-
PUT. These terminals are numbered
"3" and "2" and
are in
phase with correspondingly numbered pins in
the microphone output connector. The adjacent
ground terminal corresponds to pin 1. While the line
output may be used to drive lines of various imped-
ances (150 ohms or greater), the VU meter is cal-
ibrated for use with a 600-ohm terminated line.
OVERALL DIMENSIONS
FIGURE 2
Auxiliary
The phono jack marked AUXILIARY HI IMP OUT-
PUT is a high-impedance, high-level output designed
primarily to feed a power amplifier requiring
.5 to 2
volts, or the auxiliary or tuner input of an amplifier
or tape recorder.
NOTE: The microphone, line and auxiliary outputs
may be used simultaneously if desired, to
provide an isolated PA feed or to drive dif-
ferent pieces of equipment.
Headphone output The headphone output on the rear panel is desig-
nated HEADPHONES. A two-circuit phone jack is used
to provide a choice of level for different headphone
impedances. Normally, a single-circuit plug should be
used. If inserted only partially (to the first detent),
the available voltage is approximately 0.25 volts; the
second position will provide approximately 0.50 volts
across 1000-ohm headphones at
+4 dBm (0 VU) line
output. Crystal headphones may be used, but the level
will be the same in either jack position.
If stereo phones are used, the two-circuit plug may
be inserted completely (to second position) and the
output will appear in both phones.
VU METER When the METER SENSITIVITY switch (on rear
panel) is on the
0 VU =8 dBm FIXED position, an
output of 8
dBm on the 600-ohm line output (loaded
with 600 ohms), reads
0 VU on the meter. When the
METER SENSITIVITY switch is in the
0 VU VARIABLE
position and the
0 VU LEVEL ADJUST control is
maximum (fully clockwise), an output of
4 dBm on the
600-ohm line output (loaded with 600 ohms) reads
0 VU on the meter; at minimum position of the 0 VU
LEVEL ADJUST, fully counterclockwise, an output of
approximately -20
dBm on the 600-ohm line output
(terminated in 600 ohms) reads
0 VU on the meter.
The variable position on the METER SENSITIVITY
switch allows the VU meter to read
0 VU for outputs
ranging from -20
dBm to -I- 4 dBm (600-ohm line
terminated), by adjusting the
0 VU LEVEL ADJUST
(screwdriver adjustment on rear panel). To calibrate
the VU meter properly in applications where a level
other than the fixed level is needed, set the VOLUME
control on the M63 until the meter deflects to the
0 VU position on the loudest peaks, then adjust the
0 VU LEVEL ADJUST control for the desired output
signal level. The LEVEL ADJUST control attentuates
all outputs simultaneously (except HEADPHONES),
while the internal circuitry operates at the proper
level to insure good signal-to-noise ratio.
Page 2
ACCESSORY 30 V.D.C. The rear panel jacks (located near power cord)
provide 26 Vdc open circuit (23 Vdc at 10
mA max.)
for accessories. These jacks also are used as a power
input when using the
A67B Battery Power Supply.
CONTROLS
Volume Control
The front panel control designated VOLUME con-
trols the overall output of both high level inputs and
functions as a master volume control. When the input
device has a volume control of its own, the best
signal-to-noise ratio is obtained by turning up that
control as high as possible without encountering
distortion, keeping the M63 VOLUME control low.
Tone Control Front panel controls designated BASS and TREBLE
are standard function tone controls having a response
characteristic as shown in Figure 3.
FREQUENCY IN HERTZ
FREQUENCY RESPONSE
IN dB-TONE CONTROL CURVES
LO-CUT AND HI-CUT SET ON FLAT POSITION
FIGURE 3
Filter Controls The front panel controls designated LO CUT (Hz)
and HI CUT (Hz) are continuously variable low-pass
and high-pass filters (6 dB per octave) with a typical
response function as shown in Figure
4.
FREQUENCY IN HERTZ
FREQUENCY RESPONSE IN
dB-COMBINING,TONE CONTROL AND FILTER CURVES
FIGURE 5
In this case, the upper dashed lines show BASS
and TREBLE control position; the lower dashed lines
show HI CUT and LO CUT control settings. The solid
curve is the combined resultant response of all sett-
ings. The resultant response is obtained by subtract-
ing the lower curve (in dB) from the upper set of
curves. For instance, at 100 Hz the lower curve is
9 dB
below the
0 Reference line; subtract 9 dB from the
upper curve at 100 Hz (lowering it to
5 dB above the
0 Reference).
The resultant curve shown might be typical of a
sound system where low-frequency noise was a
problem (stage noise, etc.) and the room was relatively
dead (heavily draped and carpeted). The
low-frequen-
cy rolloff would keep objectionable thumping noises
to a minimum, while the slight increase in response
at 200 Hz will keep the system from sounding tinny.
The rise in the high frequencies will add some
presence so voices or music will have added clarity.
This is only one example of the response curves
available with the M63. An individual calculation can
be done in this manner for the other resultant curves.
WARNING
Voltages in this equipment are hazardous to life.
Refer servicing to qualified service personnel.
OPTIONAL ACCESSORIES
00 A68M MICROPHONE PREAMPLIFIER
FREQUENCY IN HERTZ
FREQUENCY RESPONSE IN dB-LO-CUT AND HI-CUT
CONTROL CURVES BASS AND TREBLE CONTROLS SET AT
12 O'CLOCK POSITION
FIGURE 4
Combining Tone and Filter Functions
The BASS and TREBLE control response charac-
teristic and the LO CUT and HI CUT response char-
acteristic may be combined to obtain a variety of
overall curves, sometimes needed for special effects
involving room acoustics, equipment equalization, etc.
Figure
5 shows an example of combining these
functions. The
A68M Microphone
Preamplifier provides a mi-
crophone input, either balanced low or high imped-
ance, or a balanced bridging line input to the M63.
The
A68M output cable is connected to one of the
M63 inputs. The
A68M mounts on the left side of the
M63 and receives its power from the M63 30-volt
DC jacks.
A68S STACKING KIT
This accessory consists of brackets for vertical
stacking of an M68 Series mixer and an M63 (or any
combination of Shure mixers or controllers). An inter-
connecting cable for combining units is included.
