Studio Technologies IFB Plus 2001 - Manual (Page 18)

Issue 7, November 2001 Model 2 User Guide
Page 18 Studio Technologies, Inc.
The Model 11A Gooseneck Microphone
is an unbalanced electret type, requiring
an external source of DC power. The
microphone utilizes a 3-conductor ¼-inch
plug for interconnection. The tip lead
brings DC power to the microphone, as
well as having microphone audio superim-
posed on it. The ring lead is microphone
common. The sleeve lead is a shield
connection.
Included with the Model 11A is a mounting
hardware kit. Included with the kit is a
3-conductor ¼-inch jack used to mate
with the microphone’s plug. At the factory
a 3-conductor wiring harness assembly
is 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 attached to the tip connection on
the jack. The other end should be con-
nected 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 terminal 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 impedance of 24k ohms. Balanced
or unbalanced signals can be connected.
The input trim pot allows signals with a
nominal level of –15 to +10dBu to be
correctly interfaced. When connecting
balanced signals the audio should con-
nect to the + and – terminals. 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 con-
nection 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
function, which is intended to prevent
acoustical feedback if the access station
is located close to the monitor loud-
speaker associated with the Model 2
Central Controller. When the monitor mute
switch is set to the ON position, the moni-
tor 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 chan-
nel 1 or 2 will be monitored. The monitor
output is accessible 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 con-
ductors 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 loud-
speaker. 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