Studio Technologies 2A 2013 - Manual (Page 28)

Issue 1, October 2013 Model 2A User Guide
Page 28 Studio Technologies, Inc.
will occur when the DC on pin 2 of the talent
amplifier output falls below a threshold volt-
age. Once the fault is removed the LED will
again light continuously. A fault will occur
when an excessive load (greater than 250
milliamperes) is presented to the output,
typically due to too many user devices be-
ing connected. A shorted interconnect cable
can also cause the output to go into its fault
condition.
While the fault condition is not desirable,
it’s actually a protection feature. Model 2A
circuitry, under microcontroller integrated
circuit control, monitors the output voltage.
If it falls below a threshold the output DC
is cycled on and off to protect the circuitry.
Leaving the output enabled continuously
during a fault condition would cause stress
to the components and possibly lead to
damage. Once the fault condition has been
removed the talent amplifier output will re-
turn to normal operation.
Using Party-Line Intercom Beltpacks
While the Model 2A’s talent amplifier output
can be used to power and send audio to
listen-only user beltpacks, such as the
Models 32A and 33A, it’s actually a “mini”
party-line (PL) power supply. It provides
24 volts DC from pin 2 to pin 1 and 200 ohm
termination impedances from pin 2 to
pin 1 and from pin 3 to pin 1. This allows
2-channel PL user beltpacks, such as the
popular RTS® BP325, to be connected.
(Up to three BP325 units can be easily
supported by the talent amplifier output’s
maximum of 250 milliamperes of current.)
Users of these PL beltpacks could commu-
nicate with each other on the two channels
as well as hearing audio from the Model
2A’s IFB channels. A little extra flexibility,
such as this PL capability, can prove useful
in special circumstances!
Configuration
Setting the Program Input
Level Trim Pots
Trim pots have a range of –4 to +14 provid-
ing a compatible range of –10 to +8 dBu.
There is no hard and fast rule on how to
best adjust the trim pots associated with the
four program inputs. As mentioned in the In-
stallation section of this guide, the trim pots
are provided to allow the relative levels of
the program input signals to be adjusted so
as to roughly match each other. This will al-
low minimal level changes when an operator
switches between the four program inputs. A
simple method of “calibrating” 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 pro-
gram material.