Studio Technologies IFB Plus 2005 - Manual (Page 15)

Model 2 User Guide Issue 8, December 2005
Studio Technologies, Inc. Page 15
attached to the jack. The wiring harness has
a red-colored wire, a black-colored wire, and
a shield wire. One end of the red wire is at-
tached to the tip connection on the jack.
The other end should be connected to the
+ terminal on the Model 22’s microphone
input. One end of the black-colored wire
is attached to the ring lead of the jack.
The other end should be connected to the
– terminal on the Model 22’s microphone
input. One end of the shield connection is
attached to the sleeve of the jack. The other
end should be connected to the SHLD ter-
minal on the Model 22’s microphone input.
Setting the input select switch to the line
position activates the line input, and the
associated input trim potentiometer. The
line input circuit is electronically balanced,
capacitor coupled, with an input imped-
ance of 24 k ohms. Balanced or unbalanced
signals can be connected. The input trim
pot allows signals with a nominal level of
–15 to +10 dBu to be correctly interfaced.
When connecting balanced signals the
audio should connect to the + and – termi-
nals. The shield wire can be connected to
the SHLD terminal associated with the mic
input. Unbalanced signals require a bit more
attention for correct operation. The signal
high lead should be connected to the +
terminal. The signal low/shield wire should
connect to both the – terminal and the SHLD
terminal. Failure to make this connection
can result is large amounts of hum being
induced into the interrupt signal.
If you have connected a signal to the line
input terminals, set the trim pot only after
installing the entire IFB system. Refer to the
Technical Notes section of this guide for
details on setting the trim pot.
The Model 22 contains a monitor mute func-
tion, which is intended to prevent acoustical
feedback if the access station is located
close to the monitor loudspeaker associated
with the Model 2 Central Controller. When
the monitor mute switch is set to the ON po-
sition, the monitor output is muted whenever
an interrupt occurs from that access station.
Monitor Output
The Model 2 contains a 4 watt monitor
amplifier which is intended to drive a small,
efficient loudspeaker. A switch on the front
panel selects whether IFB channel 1 or 2 will
be monitored. The monitor output is acces-
sible from the back panel using a ¼-inch
2-connector jack. The output can drive 8
ohm or greater loads, and is quite “hi-fi.”
Ensure that both conductors of the speaker
wiring are “floating” (isolated) from ground.
This will prevent ground loops that could
cause oscillation or other strange audio
gyrations. We recommend using a good
quality loudspeaker. If you do so we think
you’ll find the monitor output sounds quite
nice. In our lab, we tested the monitor amp
by connecting it to a JBL three-way speaker
cabinet, with a compact disc acting as our
program source. The amp, within reason,
really “kicked some tail!”
Connecting AC Mains Power
The Model 2 is factory configured to
operate from AC mains power of either 120
or 220/240 V, 50/60 Hz. In most cases,
units shipped to North America are factory
selected for 120 V operation and are sup-
plied with an internal 0.500 A, 5 x 20 mm
fast-acting fuse. Most units shipped out-
side North America are factory selected for
220/240 V operation and are supplied with a
0.250 A, 5 x 20 mm fast-acting fuse. Before
connecting the Model 2 to mains power,
determine the actual mains voltage and con-
firm that the Model 2 has been configured