10
MODIIB STEREO PROCESSOR
Convenient GROUND (GND) terminals are provided
near the outputs. A balanced subwoofer output is
available on the MODIIB to provides an easy means to
mono bridge the sub amplifier. The subbass output
may also be operated in an unbalanced configuration
by connecting to the SUB+ terminal and GROUND.
MUTING FUNCTION:
A convenient MUTE terminal on the back of the
MODIIB allows all output channels of the MODIIB to
be silenced whenever this terminal is grounded.
REMOTE FADER OPERATION:
The volume control of the MODIIB can be operated
remotely at another location, independent of the FILM
LEVEL fader. This can be accomplished by adding a
remote, linear taper 10k ohm pot (to act as a volume
control) between the REM SEND and GROUND ter-
minals on the back of the MODIIB. Connect the wiper
of the remote pot to the REM RETURN terminal.
The toggle switch on the right hand side of the Format
Card, labeled REMOTE/LOCAL, allows the operator
to select either local or remote volume control of the
MODIIB. This switch is easily accessible by removing
the four thumb screws that attach the front plate to the
MODIIB.
Note: Remote operation is for film formats only, and
will not affect the music level.
SECTION 5:
CALIBRATION
For more detailed information about setting up
SMART processors, see the
Theatre Sound for SMART
Systems guide. The Sound Systems should be turned
on for at least one hour before alignment. All doors
should be closed and the exhaust fan should be run-
ning if the MODIIB is placed in an equipment rack.
Note: Before plugging or unplugging cards in the
MODIIB during calibration, be certain power is
removed from the MODIIB. Otherwise, damage to
cards or the processor may result!
EQUIPMENT REQUIRED:
Sound Pressure level meter, real time analyzer (RTA)
with a calibrated microphone, dual trace oscilloscope,
multimeter, a tuning wand and appropriate test loops.
A CHAIN CALIBRATION
The A chain is usually considered to be the signal path
originating from the solar cell and continuing to the
processor’s master fader. This signal path includes the
preamp, noise reduction and matrix stages.
PRELIMINARY:
1. Clean soundhead optics, exciter lamp, optical lens
and solar cell before attempting a soundhead align-
ment.
2. Set exciter lamp voltage for at least 80% of rated
voltage.
BXM 9 volt 4 amp — 7.2 volts
BXN 10 volt 5 amp — 8 volts
Most foreign 6.3 volt 4 amp — 5 volts
3. Make sure film/cell spacing is approximately 1 mm
with the slit image striking the top one-third of solar
cell.
4. Connect oscilloscope and real time analyzer to the
Left and Right Preamp outputs on the rear terminals
of the MODIIB (marked LEFT PRE & RIGHT PRE).
5. Locate the Gain and Slit Loss controls on the
Preamp Card. Turn Gain controls fully clockwise.
Turn Slit Loss controls fully counterclockwise.
6. Turn the FILM LEVEL fader all the way down to
avoid excessive noises in the auditorium for the next
steps.
SOUNDHEAD ALIGNMENT:
1. Play a S.M.P.T.E. Buzz Track loop. Adjust the lateral
film guide assembly or exciter lamp assembly.
Monitor the preamp signals with the oscilloscope.
Adjust for minimum signal on the left and right chan-
nels. Refer to specific instructions in the projector
soundhead manual. Minor variations in alignment
procedure depend on the individual mechanical
design of the soundhead.
2. Play CAT.# 97 Stereo Cell Alignment Film. Move
solar cell laterally and vertically until you have
achieved minimum crosstalk between channels (see
diagram 1).
3. Repeat steps 1 and 2 until no further improvement
can be obtained.
4. Play Pink Noise side of CAT.# 69 Test Film. Switch
oscilloscope to X/Y Mode. Adjust soundhead optical
lens azimuth for narrowest diagonal trace (see dia-
gram 2). Observe the real time analyzer and focus the
lens for maximum high frequency output while main-
