Studio Technologies 740 - Manual (Page 14)

Issue 3, May 2004 Model 740 User Guide
Page 14 Studio Technologies, Inc.
Model 740
Before connecting the Model 740 to AC
mains power, determine the actual mains
voltage and confirm that the Model 740
has been configured appropriately. As
could be expected, an incompatible mains
voltage configuration could seriously dam-
age the unit. Should it be necessary to
change the unit’s operating voltage con-
tact Studio Technologies’ technical sup-
port personnel for details.
The Model 740 uses a 3-pin IEC 320
C14-compatible inlet connector to mate
with a detachable mains cord set. For
units shipped to North America and
Japan, a cord is supplied that has a North-
American (NEMA 15L) standard plug on
one end and an IEC 320 C13-compatible
connector on the other. Units bound for
other destinations require that the ap-
propriate cord set be obtained. The wire
colors in the mains cord must conform to
the internationally recognized color code
and should be terminated accordingly:
Connection Wire Color
Neutral (N) Light Blue
Live (L) Brown
Earth/Ground (E) Green/Yellow
Because the Model 740 contains no AC
mains on/off switch it will begin operation
as soon as AC mains power is connected.
Post-Installation
Calibration
Reference Tone Direct Output
If the reference tone direct output is used,
it’s important to confirm that its output
level is correct for the installation. In
most cases the output level will need
to be adjusted to match the precise
requirement of the system. This is be-
cause the load applied to the output may
well be different than the 100 k ohm load
that is applied at the factory. As previously
noted, while the output circuitry is capable
of driving loads of 600 ohms or greater,
the output level will drop slightly as the
load impedance changes, especially as
it approaches 600 ohms.
Detail of back panel highlighting reference
tone direct output connector and associated
level trim pot
Depending on the Model 740’s internal
configuration the tone frequency will be ei-
ther 400 Hz or 1 kHz. A trim potentiometer
allows adjustment of the output level over
a range of approximately +3 to +7 dBu.
The trim pot is accessible by way of a
small access hole in the back panel, adja-
cent to the reference tone direct output’s
male XLR-type connector. At the factory
this output is loaded with 100 k ohms and
then the trim pot is adjusted to give an
output level of +4 dBu.
In practice, calibrating the output level
is quite simple:
1. Confirm that the reference tone direct
output is terminated with its normal
load impedance.
2. Ensure that the Model 740 is connect-
ed to AC mains power.