Studio Technologies 74 - Manual (Page 15)

Issue 2, January 2006 Model 74/75 User Guide
Page 16 Studio Technologies, Inc.
for Surround
be performed only at the factory or by a
competent service technician.
The Model 74 uses an IEC-320 C14-
compatible connector to mate with the
AC mains cord. The wire colors in the AC
mains cord should conform to the interna-
tionally recognized CEE color code and
must be wired accordingly:
Connection Wire Color
Neutral (N) Light Blue
Line (L) Brown
Protective Earth (E) Green/Yellow
Safety Warning: The Model 74 does
not contain an AC mains disconnect
switch. As such, the AC mains cord
plug serves as the disconnection
device. Safety considerations require
that the plug and associated outlet
be easily accessible to allow rapid
disconnection of AC mains power
should it prove necessary.
As soon as AC mains power is applied, the
Model 74’s power present LED will fl ash
for a few seconds. After the completion of
a software startup interval the power pres-
ent LED will light steadily. The data active
LED on the Model 74 will fl ash once upon
power up, then briefl y light upon comple-
tion of the Model 75’s power-up sequence.
The Model 75 will go through its own
power-up sequence, lighting each LED in
secession.
Confi guration
After the physical installation has been
completed, several confi guration issues
must be addressed. On the Model 74 the
surround and stereo inputs must be cali-
brated using the trim potentiometers. The
operating parameters of the system should
be set using the Model 75 Control Con-
sole’s confi guration mode.
Level Calibration
Sixteen 15-turn trim potentiometers are
located on the front panel of the Model 74
Central Controller. Taking time to care-
fully adjust the trim pots will ensure that
accurate monitoring can take place. Each
trim pot allows input signals with a nominal
level of –12 dBV to +6 dBu to be utilized.
With care, it’s easy to calibrate the sur-
round and stereo inputs to within one-
quarter of a dB of the desired value.
The monitor outputs are used as the
measuring point when adjusting the trim
pots. A laboratory-grade audio level me-
ter or equivalent is required for accurate
calibration. In addition, the audio sources
connected to the inputs must be able to
generate continuous audio signals at their
nominal operating level.
Procedure
This procedure will calibrate the surround
and stereo input channels. The trim pots
will be adjusted in groups corresponding
to their associated input sources.
1. Begin by turning the audio amplifi ers
or amplifi ed speakers to their off state.
This will protect the loudspeakers and
the operator’s ears from possible
damage.
2. Rotate the level control on the Model
75 to the fully clockwise (maximum)
position.
3. Using the Model 75 Control console,
select Surround A as the input source
and Speaker System A as the selected
monitor output.