Studio Technologies 2A 2015 - Manual (Page 22)

Issue 2, March 2015 Model 2A User Guide
Page 22 Studio Technologies, Inc.
will have to be provided. The simplest
method is to use a short section of ribbon
cable and multiple 9-pin insulations-
displacement (IDC) connectors. Depend-
ing on the specific installation, the “break
out” assemblies can be connected directly
to the access station connectors on the
Model 2A units, or can be “downstream” at
one of the Model 24s.
The Model 24 Access Station contains two
mode switches that must be set. The input
select switch allows the unit to be set for
compatibility with a mic input or a line-
level input. In many cases the Model 11A
Gooseneck Microphone, available as an
option from Studio Technologies, will
be used with a Model 24. Setting the
switch to the MIC position activates the mic
input terminals. The mic input is configured
only for use with unbalanced electret
microphones. The + terminal on the mic
input provides current limited 5 volts DC
to power the electret microphone. The –
terminal is connected to the microphone’s
low signal lead. The connection marked
SHLD is intended for the shield wire of the
microphone cable; it doesn’t carry signal. A
dynamic microphone must not be connect-
ed to the mic terminals; it won’t provide the
correct signal level and damage to the mic
may occur.
The Model 11A Gooseneck Microphone is
an unbalanced electret type, requiring an
external source of DC power. The micro-
phone utilizes a ¼-inch 3-conductor plug
for interconnection. The tip lead brings DC
power to the microphone, as well as hav-
ing microphone audio superimposed 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. This kit contains a ¼-inch
3-conductor 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 connected
to the + terminal on the Model 24’s micro-
phone 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 24’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 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 over the range
–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 can be connect-
ed 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 im-
provements will be found by connecting the
low/shield lead to both the – and the SHLD
terminals. 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 Configuration section of this guide for
details on setting the trim pot.