Studio Technologies 5120 2014 - Manual (Page 6)

Issue 5, October 2014 Model 5120 User Guide
Page 6 Studio Technologies, Inc.
Model 5120
Line/IFB Output Module
IFB amplifiers, such as the Models 32A,
33A, or 34A from Studio Technologies,
Inc. The 2-channel IFB output provides
signal common on one pin, +28 volt DC
power with superimposed analog audio on
a second pin, and analog audio only on a
third pin. This complies with a long-popular
broadcast-standard implementation.
Model 5120 Line/IFB Output Modules
do not include a mounting enclosure or
chassis. They are intended for mounting
in custom 19-inch rack panels, equipment
boxes, broadcast furniture, or other spe-
cialized settings. It is expected that integra-
tion firms will create applications that use
Model 5120 modules as part of complete
broadcast, production, corporate, and gov-
ernment solutions.
Separate audio inputs are provided for
interfacing with analog and digital audio
sources. The two analog inputs are bal-
anced and compatible with line-level sig-
nals. An unbalanced AES3 digital audio
input allows the connection of two audio
channels. Input source selection is auto-
matic. If an AES3 digital audio source
is connected it will have priority. Two 7-
segment LED meters provide the user
with an indication of the input levels.
The Model 5120’s audio performance is
very good. Low-noise, wide dynamic-range
circuitry ensures that the input audio qual-
ity is preserved. The audio from the digital
audio input is routed to a high-performance
digital-to-analog conversion (DAC) section
that supports sample rates of up to 48 kHz
with a bit depth of up to 24. The outputs
of the analog inputs or DAC circuitry are
routed to two line-level analog audio output
sections. These provide the line-level,
balanced (differential), ESD-protected,
capacitor-coupled output signals.
The two analog signals from the selected
input channels are also routed to the IFB
circuitry. One channel is used to modulate
the DC power source circuitry. The second
channel is routed to a single-ended (unbal-
anced) line-driver circuit. The IFB power
source circuitry provides a low-noise,
current-limited source with a nominal
28 volt DC output. This is essentially identi-
cal to that created by “big time” broadcast
IFB systems. Logic circuitry contained
within the Model 5120 monitors the DC
output voltage. Should a low-voltage/over-
current condition be detected the DC
output enters a protection mode. Once the
fault condition is removed normal opera-
tion will again resume. An LED, located on
the Model 5120’s front panel, provides an
indication of the IFB output’s status. Note
that for additional flexibility, the source
impedance of both IFB output channels is
200 ohms, allowing intercom “beltpacks” to
also serve as listen-only devices.
All audio inputs and outputs were carefully
designed for use in permanent as well as
field applications. Filtering on the inputs
minimizes the chance that radio frequency
(RF) energy will interfere with audio input
sources. Other components were included
to address ESD (“static”) and DC over-
voltage conditions The DC power input is
protected from accidental polarity reversal.
The Model 5120 requires an external
source of nominal 12 volts DC for opera-
tion. The acceptable input voltage range
is 10 to 18 allowing a variety of power
sources to be utilized. Internal power sup-
ply circuitry within the Model 5120 creates
the voltages required for the analog audio,
digital audio, and IFB circuitry.
Standard connectors are used throughout
the Model 5120. Line-level and IFB output