Studio Technologies 2A 2015 - Manual (Page 30)

Issue 2, March 2015 Model 2A User Guide
Page 30 Studio Technologies, Inc.
other. This will allow minimal level changes
when an operator switches between the four
program inputs. A simple method of “cali-
brating” the program input trim pots is to:
1. Begin by connecting an audio level meter
to the line output of IFB channel 1. The
meter will connect by way of an interface
cable that provides a 3-pin male XLR.
Set the meter to display the audio sig-
nal level in terms of dBu, i.e., level in dB
referenced to 0.775 volts RMS with no
defined load impedance.
2. Set the front-panel program level control
associated with IFB channel 1 to the
“2-o’clock” position (70 percent of
rotation).
3. Set the four program level trim pots,
accessible by way of holes in the back
panel, to their center (50% of their
rotation) position.
4. Activate the four program sources such
that they are providing signals at their
normal operating level. To clarify, send
signals from these four sources, at their
normal levels, to the four Model 2A pro-
gram inputs. These signals can be in the
form of alignment tones or actual program
material.
5. Use the front-panel program select
switches to select, one at a time, the four
program inputs. The line output should
give an output level of +4 dBu nominal,
with +8 to +12 dBu probable on peaks.
The actual output level is not important
and a lower level is much better than a
“hotter” average level.
6. After observing the relative strengths of
the four sources, use one or more of the
trim pots, if required, to get an equal aver-
age level from the four sources.
7. If you don’t have an audio level meter
handy, or if you’re not concerned about
exact calibration, use one of the LED level
meters on the front panel to set the trim
pots. Actually, if your ears are pretty good
use them, and no meters, to set the trim
pots to get equal levels. That’s what we
would do if we were in the field! Confirm
your subjective adjustment with the LED
meter and you should be set.
Setting the Line-level Trim Pot
on the Model 22 and Model 24
Access Stations
The Model 22 and Model 24’s line input
circuitry allows balanced and unbalanced
signals with a nominal level of –15 to +10
dBu to be correctly interfaced. The system
is designed to have an access station send
interrupt signals at a signal level of –10 dBu
to the Model 2A Central Controller. A level
adjustment trim pot on the Model 22 and
Model 24 allows the various signal levels
to be adjusted to give the desired signal
strength. Set the trim pot only after installing
the Model 2A and associated Model 22 and
Model 24 units. The calibration procedure is
as follows:
1. Begin by connecting an audio level
measuring device across the test points
labeled COM and AUDIO on the Model
22 or Model 24’s circuit board. Set the
meter to display the audio signal level in
terms of dBu, i.e., level in dB referenced
to 0.7746 volts RMS with no defined load
impedance.
2. While speaking into the microphone,
headset, or other device that produces
the line-level signal, adjust the trim
pot to give an average level of approxi-
mately –10 dBu as shown on the meter.