Studio Technologies 750 - Manual (Page 20)

Issue 3, May 1997 Model 750 User Guide
Page 20 Studio Technologies, Inc.
Model 750
0dBu, to serve as the “0” reference. While
Studio Technologies is not excited about
such a prospect, it can certainly be
achieved. There is one serious downside
to changing the nominal operating level;
the limiter/compressor threshold. The
limiter/compressors are designed to
activate at approximately 6dB above the
Model 750’s internal operating level,
corresponding to an output level of
+10dBu. The threshold is not factory
calibrated and is not easily modified in the
field. If, as an example, the meters are re-
calibrated for a nominal output level of
0dBu, the limiter/compressors will now
activate at 10dB above this new nominal
level. Prior to changing the operating level,
a discussion with personnel at the factory
may be warranted. Call us for a chat!
While not difficult, meter calibration is a bit
tedious:
1. Ensure that mains power is connected
to the Model 750.
2. Place the main output limiter/compres-
sors to the off state by placing the
button labeled LIMITER to the out
position.
3. Activate the setup section’s single tone
output by placing the single tone
button to the on (in) position. The voice
and multi-tone buttons should be in
their off (out) position.
4. On the setup section, place the main
bus assignment button to the on (in)
position.
5. Select the main bus as the VU meter
source by placing the meter source
button to the monitor (in) position and
selecting main stereo. This makes the
meters most accurate when they are
monitoring the main bus via the moni-
tor section. If you wish to have the
meters most accurate when they are
connected directly to the main bus, set
the meter source button to the main
(out) position.
6. Designate main output 1, 2, or, in
rare circumstances, 3 as the desired
“primary” output. This is the output that
the meters will be calibrated against. If
main output 3 is selected, set its output
level button to the line (in) position.
7. Confirm that the left and right channels
of the designated main output are
terminated with their normal load
impedance.
8. Using an appropriate adapter cable,
connect an audio level meter directly
across the left channel of the desig-
nated main output. Ensure that the
meter connection does not remove the
normal load. The level meter must be a
precision device that’s intended for
audio use—a general-purpose volt-
meter is not adequate!
9. Carefully observing the audio level
meter, set the main bus left channel
master output control so that the out-
put level matches the desired nominal
operating level. In most cases this will
be +4dBu.
10.Observing the Model 750’s left channel
VU meter, adjust the left channel meter
trim pot to give 0 VU.
11.Repeat steps 8 through 10, this time
for the right channel.