INSTALLATION & OPERATION
15
You can verify that the LED meters are indicating correctly
by connecting an AC voltmeter to the LEFT PRE (TP7) and
RIGHT PRE (TP8) test points located on the bottom side of
the front of the main circuit board between connectors J1
and J2. Ground (TPG1) is located to the left of J1. You
should read between 300 to 325mVAC at these test points.
Bypass Setup
Bypass mode generates mono sound in the Center channel.
It is activated by pressing the red rocker switch to the
BYPASS position.
1. Run a film soundtrack.
2. Listen to the CENTER channel on the booth monitor.
3. Switch from Normal to Backup.
The red Backup Switch (SW2) is mounted on the front right
of the main board, behind the front panel. Pushing the
switch to the right is BYPASS mode, to the left is NORMAL
mode.
4. Adjust the BYPASS level pot (on the left front side of the
main board) to achieve equal levels while switching from
Normal mode to Bypass mode.
B-CHAIN CALIBRATION
The B Chain Calibration is generally considered to be the
signal path from the processors master fader to the speak-
ers. This signal path includes the equalizers and output
stage. Before continuing with the B Chain Calibration,
check the wiring of all auditorium speakers to make sure
the phase is correct.
Preliminary
Special Note: If you will be installing an external digital
decoder, do so AFTER setting house levels. See the DIGI-
TAL LEVEL SETTINGS at the end of the B CHAIN CALI-
BRATION section for more information.
1. Select STEREO A by pushing the appropriate button on
the front panel.
2. Set the FADER to the one o clock position.
Equalization and House Levels
The equalizers are normally shipped with the individual
trimpots set for a flat frequency response. The octave
equalizers used for the stage channels are capable of
cutting and boosting each frequency ±10 dB. The individual
trimpots are single turn types, with the mid position of each
pot being flat (unity gain).
The MOD 7a has a built in Pink Noise Generator on the
Circle Surround Matrix Board. See pages 8 and 9 for a
description of the pink noise and time delay switches
Set the pink noise channel switches (SW2) on the Circle
Surround Matrix Card to the correct setting for the channel
you wish to equalize. Select the
STEREO SR
format.
Perform the channel equalization using the trimpots
located inside the front panel.
The
LO
trimpot in each EQ
section mainly affects frequencies below 100Hz, and the
HI
trimpot mainly affects frequencies above 10kHz.
After equalization of the each stage channel, adjust its
output level using the
L
,
C
, and
R
output trimpots on the
right front of the main circuit board so that 79 dBc spl is
measured in the auditorium for each channel.
If you are
NOT
using the
EX
feature, follow this procedure
for the Left Wall Surround and Right Wall Surround
channels. Adjust equalization as you normally would. Then
set the
LW
and
RW
level trimpots to obtain 76 dBc spl in
the auditorium for each channel.
If you
ARE
using the
EX
feature, follow this procedure for
the Left Wall Surround, Right Wall Surround, and EX
channels. Turn
OFF
the rear channel amplifier (or discon-
nect the rear speakers from the rear amplifier). Adjust
equalization as you normally would. Then set the
LW
and
RW
level trimpots to obtain 76 dBc spl in the auditorium
for each channel.
Right side trimpots (Music, Digital, and Main output levels)
and Emergency Bypass switch
