Studio Technologies IFB Plus 2001 - Manual (Page 26)

Issue 7, November 2001 Model 2 User Guide
Page 26 Studio Technologies, Inc.
is maintained. The interrupt audio is pro-
cessed by the compressor/limiter so as
to prevent the talent from being “blasted”
by an excessive interrupt level. In special
cases, it may be desirable for the program
audio also to be processed by the com-
pressor/limiter. Provision has been made
on the Model 2’s circuit board to imple-
ment this change.
A possible use of this alternate routing is
where the Model 2 is consistently used in
locations where the talent is exposed to
loud ambient sound levels. Increasing the
average program level by processing it
with the compressor/limiter can increase
intelligibility. However, a serious side
effect is that the processed program audio
can prove to be much more fatiguing to
the ear. The talent may complain that the
IFB feed seems to be “annoying.” Be
careful before going ahead and changing
the signal flow.
The following procedures must
be performed by a qualified
technician. Operating the Model
2 with the cover removed exposes the
technician to points in the power input
section with hazardous voltages.
1) Ensure that the mains power cord
is removed from the Model 2’s power
connector on the back panel.
2) Remove the top cover via the four 6-32
button head cap screws.
3) Referring to page 8 of the Model 2’s
schematic diagram, find the two resistor
identification numbers for the resistors that
implement the standard audio routing.
Remove these two resistors from the
circuit board.
4) Now, referring to page 6 of the sche-
matic diagram, find the resistor identifica-
tion numbers for the resistors that
implement the optional audio routing.
5) After acquiring two 2K00 resistors
(2000 ohm, 1%, ¼-watt), prepare them for
insertion into the circuit board. With care,
the resistors can be added without remov-
ing the circuit board from the chassis.
Bend the leads so that they are ½-inches
apart, allowing them to easily drop into
the resistor locations. Trim the leads so
that once inserted and soldered into the
board, the ends of the leads will not touch
the chassis below the board. Again, en-
sure that the ends of the straps do not
extend below the circuit board so as to
touch, or even come near the bottom of
the chassis. Failure to heed this warning
can result in operational problems.
6) Replace the top cover and secure
it using the screws.
7) Reconnect the mains power and check
the Model 2 for correct operation.
Nominal Input Level—Program and
Auxiliary Audio Inputs
From the factory, the nominal input level
of the program and auxiliary audio inputs
is +4dBu. This level, along with the
±8dBu level trim adjustment, allows most
signals to be correctly interfaced. There
may be the rare case where an audio
source with a lower nominal signal level
may need to be connected. A simple
change can reduce the nominal input level
of any of the four program inputs, or the
auxiliary audio input. To reduce the nomi-
nal input level from +4dBu to –2dBu
change the differential receiver integrated
circuit from the SSM-2143 to the SSM-
2141. The ‘2143, used in the stock Model