Studio Technologies 5121 - Manual (Page 10)

Issue 3, October 2014 Model 5121 User Guide
Page 10 Studio Technologies, Inc.
Model 5121
Line/IFB Output Module
–10 dBu output levels respectively. The bal-
listics of the meters is also different, being
a cross between VU and peak.
The four green LEDs indicate that the out-
put levels are in the normal range. The two
yellow LEDs light when the signals are 6 to
approximately 17 dB above the reference
level. The red LEDs, labeled “18,” will light
when the output levels have come close to,
or have reached, the maximum level. An
optimal input signal will result in the four
green LEDs lighting almost solidly with the
yellow LEDs lighting only on peak signals.
The red LED lighting is not a good thing
and indicates that the input signal level
must be reduced.
Line Outputs
The line outputs are designed for general-
purpose use which could include connect-
ing to externally-powered listen-only user
beltpacks, transmitters associated with
wireless in-ear monitors, audio consoles,
or amplified speakers. The audio qual-
ity is such that using the line outputs for
on-air applications would be appropriate.
The outputs are analog, electronically bal-
anced, capacitor coupled, and will perform
optimally when driving loads of 2000 (2 k)
ohms or greater. When using Model 5121S
(SMPTE-compatible) modules the line
output level will be +4 dBu when a signal
at reference level is applied to the input.
(A SMPTE reference level signal will either
be +4 dBu for an analog audio source or
–20 dBFS for a digital audio source.) With
Model 5121E (EBU-compatible) modules
the line output level will be 0 dBu when
an input signal at reference level is applied.
(An EBU reference level will either be
0 dBu for analog or –18 dBFS for digital.)
The Model 5121 provides two 3-pin male
XLR connectors for interfacing with associ-
ated equipment. Pin 2 should be connected
as signal + (high), pin 3 as signal – (low),
and pin 1 as common/shield. To connect to
an unbalanced load use pin 2 as signal +
(high) and pin 1 as low/shield. Pin 3 should
be left unconnected. To clarify, for correct
unbalanced operation it is important not to
connect pin 3 to anything, e.g., do not con-
nect pins 1 and 3 together.
The line output circuitry is protected from
damage should a moderate DC voltage be
applied. For example, no damage will occur
if a Model 5121’s IFB output (28 volts DC)
is accidentally connected to one of the line
outputs. This protection would also be effec-
tive should a party-line intercom circuit or
microphone P48 phantom power signal be
accidentally connected to a line output.
IFB Output
One or more listen-only broadcast-standard
IFB devices can be connected to the IFB
output. The only restriction on the number
of units that can be connected is that the
total current draw must be equal to or less
than 120 milliamperes. Devices such as
the Studio Technologies’ Models 32A,
33A, or 34 are directly compatible and
will provide excellent performance. While
not cost-effective, it’s also possible to con-
nect intercom beltpacks such as the RTS®
BP325 as listen-only devices.
An interesting Model 5121 characteristic
is that its IFB output maintains a 200 ohm
impedance on both pin 2 and pin 3. This
effectively creates a low-current party-line
intercom power supply. With this capability
two BP325 beltpacks connected to a Model
5121 IFB output cannot only listen to the
IFB signals but also communicate between