Manual

Model 41 User Guide Issue 3, November 2013
Studio Technologies, Inc. Page 5
Introduction
The Model 41 is designed to create
broadcast-standard IFB outputs from line-
level audio sources. The unit’s primary
application is to interface analog outputs
associated with digital matrix intercom
systems with broadcast IFB user devices.
The Model 41 creates four independent
IFB outputs. Each IFB output provides DC
power and two analog audio signals to
support the connected IFB user devices.
The Model 41’s audio quality is excellent;
little hiss, hum, or other artifacts are pres-
ent. To ensure optimal operation, the unit
provides resources for visually and audibly
monitoring the audio output signals. In ad-
dition, the DC output voltage is monitored
for fault conditions.
Installation of the Model 41 is very simple.
Audio input connections are made using
a 25-pin D-subminiature connector. The
IFB output circuits interface using standard
3-pin XLR connectors. The compact, one-
rack-space package is constructed using
rugged steel and aluminum components.
The unit’s AC mains power input can range
from 100 to 240 volts, 50/60 hertz. This
“universal input” ensures correct operation
virtually anywhere in the world.
Figure 1. Model 41 Interface front and back views
There may be persons not familiar with the
term IFB. That’s not unreasonable as it’s a
somewhat obscure acronym for interrupt-
ible foldback. On its own, the term foldback
is an alternate way of describing a cue or
monitor function. Adding “interruptible”
before it means that the cue source can be
temporarily replaced with an audio signal
originating from a producer, director, or
other production personnel. IFB outputs
are often used in the broadcast industry
for talent cueing applications, both in
studio and field settings.
Both “dry” and “wet” IFB outputs can be
deployed and their characteristics are
worth reviewing. The term “dry” IFB typical-
ly refers to a transformer-balanced line-lev-
el audio circuit with a nominal level in the
range of 0 to +8 dBu. This is essentially a
standard analog audio circuit that is com-
monly used to interconnect audio equip-
ment. The term “wet” IFB refers to a circuit
that combines DC power and one or two
channels of analog audio. The DC power
source is typically in the range of 30 to 32
volts. The audio is unbalanced with a typi-
cal nominal level of –10 dBu. The Model
41 implements “wet” IFB outputs. As such,
in this user guide the term IFB will always
indicate this type of circuit.