Shure SE30 - Manual (Page 28)

SERVICE INSTRUCTIONS (Cont’d)
C. Set the Meter switch (8) to VU and the VU Range
switch (4) to +4. Adjust VU CAL trimmer poten-
tiometer (R529) for a 0 VU meter reading. Cali-
bration is complete.
STEREO SYNCHRONIZATION
Two SE30’s may be synchronized to operate together
for two-channel stereo applications. With the Stereo Par-
allel jacks (23) connected together and the adjustment
below performed, the two units will respond equally to the
sum (left and right) signal to minimize apparent stereo
image shift. After synchronization, the two units will track
together over at least a 20 dB compression range. It is in-
tended that the two units be supplied with a properly bal-
anced and mixed stereo signal from a separate mixer or
other source.
The synchronizing adjustment procedure may be per-
formed upon two properly calibrated SE30’s as outlined
below. The same equipment needed for calibration is
used for this procedure, except that an external audio
generator is a necessity. A second cable for connecting
the generator to the input connector also is required.
ADJUSTMENT:
1.
2.
3.
4.
5.
6.
7.
Connect the Input 1 connectors (13A) of both units
simultaneously to the audio generator, observing
proper phasing. Cables should be wired such that
input connector pins 1 and 3 are to the low side of
the generator and pin 2 is to the high side. Set the
Mic/Line input Switches (14A) appropriately.
Set the output of the audio generator for the expected
signal level to be applied to the units. This will be ad-
justed as follows to correspond with 10 dB of com-
pression.
Set Output (3) and Input (1) controls to zero, and Re-
sponse Rate controls (6) to the same setting on both
units, preferably between 2 and 5. Set VU Range
switches (4) and Input 1 Lo-Cut Filter switches (1A)
the same on both units, as required. Set Comp.
switches (22) to ON and Gated Memory switches (21)
to DISABLE. Set Meter switches (8) to VU.
Remove the top covers of both units and apply power.
Measure the signal voltage at terminal A of P.C. Board
3 (referred to as E3A) of one unit. Rotate the Input 1
control (1A) of this unit until E3A is -30 dBv (31.6 mv).
Measure E3A of the second unit and set its input 1
control (1A) for the same reading. Do not readjust
either input 1 control after this step.
Set the Output control (3) of the first unit for a meter
reading of 0 VU. Repeat for the second unit.
Connect the Stereo Parallel jacks (23) of the two units
together, using a phono pin plug shielded jumper
cable.
8.
9.
10.
11.
12.
13.
14.
After 30 seconds, observe the VU meter readings of
the two units and note which unit’s meter reading has
increased above 0 VU. Slowly rotate R212 of this unit
clockwise until its VU meter reads 0 VU. Allow 30
seconds for meter reading to stabilize.
Reduce generator output until E3A of this unit is -40
dBv (10mv) and set Meter switch (8) to DB COMP.
Adjust R213 for a reading of 0 on the dB Compression
scale of the meter. Do not disturb any adjustments on
the other unit.
Increase generator output until E3A of this unit is -20
dBv (100 mv). Set both Meter switches (8) to DB
COMP. and observe readings of both meters.
Short circuit the output of the audio generator and
note the time required for the meter readings of each
unit to fall to 0 DB Compression. Remove the generator
short circuit and allow the meter readings to rise and
stabilize.
Adjust the Response Rate control (6) of one of the
units in the appropriate direction to make the two
meter fall times equal and repeat Step 11 to check the
results.
Repeat Steps 11 and 12 until meter fall times are equal.
The settings of the two Response Rate controls may be
somewhat different because of individual component
variations between units.
Replace the top covers of both units.
OPERATION:
After performing the above adjustments, do not disturb
any of the Input, Output, or Response Rate control settings
thus established. If the Gated Memory feature is desired,
set the Gated Memory switches (21) on both units to ON.
The units may now be fed from a balanced, mixed, stereo
source whose level will determine the amount of compres-
sion as indicated on the DB Compression meters of the
SE30’s. Because of individual component variations be-
tween units, the two meters may indicate somewhat dif-
ferently, but both units will operate similarly if adjusted as
outlined above.
Since stereo operation is recommended for only a single
pair of inputs, it may be desirable to improve the operating
signal-to-noise ratio by disabling the two unused input
channels on each unit. This procedure is described in the
Modifications section below.
If it is necessary to change the Response Rate control
settings to compensate for different types of program
material, the timing of the two units should be adjusted to
be equal. This may be done without removing the covers
by applying a signal from an external audio generator to
the inputs of both units simultaneously. Set the Gated
Memory switches (21) of both units to DISABLE and ad-
just the generator output for a DB Compression reading of
approximately 20 on either unit’s meter. Set the Response
Rate control (6) of one unit to the number desired, then
adjust the Response Rate control of the other unit as de-
scribed in Steps 11, 12, and 13 above.
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