Studio Technologies 5120 2011 - Manual (Page 6)

Issue 3, November 2011 Model 5120 User Guide
Page 6 Studio Technologies, Inc.
Model 5120
Line/IFB Output Module
Model 5120 Line/IFB Output Modules do
not include a mounting enclosure or chas-
sis. 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
government solutions.
Separate audio inputs are provided for
interfacing with analog and digital audio
sources. The two analog inputs are bal-
anced (differential) and compatible with
line-level signals. An unbalanced AES3id
digital audio input allows the connection
of two digital audio channels. A configura-
tion DIP-type switch allows selection of the
desired input signal. Two 7-segment LED
meters provide the user with an indication
of the inputs 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 out-
put 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 through-
out the Model 5120. Line-level and IFB
output connections are made using 3-pin
male XLR-type connectors. The two ana-
log audio inputs use a 5-position, 0.1-inch
“header” connector. A DIN 1.0/2.3 coaxial
connector is used to interface with the digi-
tal audio input. The DC power input con-
nections use a 4-position, 0.1-inch header.
Low-cost IDC (insulation displacement)