Studio Technologies 46A - Manual (Page 11)

Model 46A User Guide Issue 1, September 2014
Studio Technologies, Inc. Page 11
4-Wire Line Inputs
As previously mentioned, each of the
Model 46A’s two interfaces allows two
analog line-level audio sources to be con-
nected. The source for these signals will
typically be ports on a matrix intercom
system. It’s also possible that the signals
will come from other devices, such as a fi-
ber optic or copper-based audio transmis-
sion system. The 4-wire input circuitry is
balanced, capacitor coupled, transformer
isolated, and has an impedance of 13 k
ohms. The line inputs are compatible with
signals that have a nominal level of 0, +4,
+6, or +8 dBu. Configuration switches,
located on the Model 46A’s front panel,
allow the circuitry to be adjusted to match
the connected nominal level. The switches
work in tandem to control both the input
and output nominal levels.
Audio sources are connected to the line
inputs by way of 3-pin female XLR con-
nectors which are located on the unit’s
back panel. Refer to Figure 1 for a detailed
view. Note that pin 1 of these connectors
is internally connected to the Model 46A’s
earth/chassis ground point.
Prepare the mating connectors (males)
so that pin 2 is signal high (+ or hot),
pin 3 is low (– or cold), and pin 1 is shield.
If connecting a source in this manner results
in hum or noise it’s possible that removing
the shield connection from pin 1 can elimi-
nate the issue; “floating” pin 1 will remove
a potential ground current path from the
Model 46A’s earth/chassis ground point
through the shield of a cable. Also, if a hum
or noise issue does arise be certain to con-
firm that, unless absolutely necessary, the
mating connector’s “shell” isn’t connected
to the cables’ shield or pin 1. Termination of
this “fourth” pin of a 3-pin XLR connector is
often the cause of seemingly inexplicable
noise issues.
With an unbalanced source connect pin 2
to signal high (+ or hot) and both pins 1
and 3 to shield. If connecting an unbalanced
source in this manner results in hum or
noise, connect pin 2 to high (+ or hot) and
pin 3 to shield; leave pin 1 unterminated.
4-Wire Line Outputs
Each of the Model 46A’s two interfaces
provides two analog line-level audio outputs.
These outputs are intended to be connected
to inputs on the devices associated with the
4-wire audio signals. The outputs are ca-
pacitor coupled, transformer balanced with
a nominal level of 0, +4, +6, or +8 dBu. As
previously mentioned, the 4-wire nominal
level configuration switches, located on the
Figure 1. Detail of back panel showing line inputs and outputs