Studio Technologies IFB Plus 2005 - Manual (Page 10)

Issue 8, December 2005 Model 2 User Guide
Page 10 Studio Technologies, Inc.
Locating the Unit
Physical access and mechanical noise are
the primary factors when choosing a mount-
ing location. You don’t want a cooling fan
blowing directly onto the internal micro-
phone, nor do you want the microphone at
the level of your navel. It is also a good idea
to keep the Model 2 physically separated
from other electronic devices that produce
strong electrical fields. As a device that
contains high gain audio stages, hum and
noise pickup is possible through the chas-
sis and associated cabling. Locating the unit
away from devices such as power amplifi-
ers, power transformers, and lighting con-
trols will help to avoid pickup of unwanted
signals. Precautions were taken to limit the
Model 2’s bandwidth, minimizing the chance
for RF pickup problems.
Mounting
The Model 2 is intended for rack mount-
ing, requiring one 1.75-inch rack space. It
weighs a bit over 10 pounds (4.7 kg), and
operates on either 120 or 220/240 V, 50/60
Hz. The unit is secured to the front mount-
ing rails of an equipment rack using two
mounting screws per side. In addition to the
front mounting “ears,” we encourage you to
secure the Model 2 from the back. Provision
has been made for this to be easily ac-
complished. On each side of the Model 2’s
chassis are two threaded fasteners intended
to secure user-fabricated mounting bars or
brackets. Use standard 8-32 screws to se-
cure the mounting brackets to the Model 2’s
chassis. To prevent damage to the Model
2’s “guts,” limit the screw length so that the
threads extend into the chassis a maximum
of ¼-inch. Refer to Figure 1, located at the
end of this guide, for a mechanical drawing
detailing the fastener locations. This drawing
will assist you in fabricating the mounting
brackets.
Program Inputs
The Model 2 allows four line-level program
audio sources to be connected. The input
circuitry is designed for a nominal input level
of +4 dBu. A trim potentiometer is associ-
ated with each input, giving a ±8 dB adjust-
ment range. The trim pots are not intended
for precise calibration, but strictly to allow
the program input signals to be adjusted to
the same relative level. A little attention to
setting the trim pots will give better opera-
tional performance. It will allow an operator,
using the front-panel program switches, to
rapidly change program inputs, while not
giving large changes in level to users listen-
ing to the IFB channel. It is anticipated that
the trim pots will be adjusted only upon ini-
tial installation or during maintenance, and
are not considered an operator function.
Refer to the Technical Notes section of this
guide for details on setting the trim pots.
Program audio connections are made via
four 3-pin female XLR-type connectors lo-
cated on the back panel. The program input
circuitry on the Model 2 is direct coupled,
electronically balanced with an input imped-
ance of 24 k ohms. Prepare the mating con-
nectors so that pin 2 is positive (+ or hot),
pin 3 is negative (– or cold), and pin 1 is
shield. With unbalanced signals connect pin
2 to positive, and pins 1 and 3 to shield.
Auxiliary Audio Input
The Model 2 allows an auxiliary line-level
audio source to be connected for use with
the voice operated (VOX) interrupt function.
Identical to the program inputs, the auxil-
iary input circuitry is designed for a nominal
signal level of +4 dBu. A trim pot is associ-
ated with the auxiliary input, giving a ±8 dB
adjustment range. The pot is not intended
for precise calibration, but strictly to allow