Model IFB Plus Series Talent Amplifier User Guide

Model 2A User Guide Issue 2, March 2015
Studio Technologies, Inc. Page 29
Access Stations
It’s important to thoroughly test all con-
nected Model 22 and/or Model 24 Access
Stations. Is the interrupt audio loud and
clear? Observe the status lamps inside the
pushbutton switches. Do the appropriate
lamps light fully bright when an interrupt
takes place? If an access station is config-
ured to mute the Model 2A’s monitor out-
put, ensure that the monitor speaker mutes
during interrupt activity.
Audio Quality
In all cases, you should hear clear, click-
free audio. We intended the Model 2A
to sound great—if not, call us for technical
help. A completed installation should
be reliable, easy to use, and perform
to high sonic standards. Questions and
comments from the field are welcomed
and encouraged!
Operating Notes
Talent Amplifier Output
Should the Model 2A’s talent amplifier out-
put experience a fault condition the power
LED will flash on and off. Technically this
will occur when the DC on pin 2 of the tal-
ent amplifier output falls below a threshold
voltage. Once the fault is removed the LED
will again light continuously. A fault will oc-
cur when an excessive load (greater than
250 milliamperes) is presented to the out-
put, typically due to too many user devices
being 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 return to normal operation.
Using Party-Line Intercom Beltpacks
While the Model 2A’s talent amplifier out-
put 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
providing 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 Installation section of this guide, the
trim pots are provided to allow the rela-
tive levels of the program input signals to
be adjusted so as to roughly match each