Studio Technologies IFB Plus 2007 - Manual (Page 18)

Issue 9, January 2006 Model 2 User Guide
Page 18 Studio Technologies, Inc.
attached to the sleeve of the jack. The other
end should be connected to the SHLD ter-
minal on the Model 24’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 balanced, transformer
coupled, with an input impedance of 40 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 con-
necting balanced signals the audio should
connect to the + and – terminals. The shield
wire can be connected to the SHLD terminal
associated with the mic input. Unbalanced
signals can be connected so that the signal
high lead is connected to the + terminal and
the signal low/shield lead connects to the
– terminal. If this results in hum or noise it’s
possible that improvements will be found by
connecting the low/shield lead to both the
– and the SHLD terminals. If you have con-
nected 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 24 contains a monitor mute func-
tion, which is intended to prevent acoustical
feedback if the access station is located
close to monitor loudspeakers associated
with the Model 2 Central Controllers. When
the monitor mute switch is set to the ON po-
sition, the monitor outputs mute 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 two-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
correctly, as an incorrect setting could seri-
ously damage the unit. Should it be neces-
sary to change the unit’s operating voltage
refer to the Technical Notes section of this
guide. Because the Model 2 contains no
power switch it will start operating as soon
as mains power is connected.
The Model 2 uses an IEC standard connec-
tor to mate with the AC mains cord. Normal-
ly the cord supplied has a North American
standard plug at one end and an IEC con-
nector at the other. In non-North American