Studio Technologies 47A - Manual (Page 12)

Issue 1, September 2014 Model 47A User Guide
Page 12 Studio Technologies, Inc.
and the line inputs. The 4-wire line outputs
are capable of driving inputs that have
impedances as low as 600 ohms, however
connecting to loads of 2 k ohms or greater
is preferred. The line outputs are connected
by way of 3-pin male XLR connectors which
are located on the Model 47A’s back panel.
Refer to Figure 1 for a detailed view.
The mating connectors (females) should
be prepared so that signal high (+ or hot)
is expected on pin 2. Signal low (– or cold)
should be expected on pin 3. A cable’s
shield can be connected to pin 1. How-
ever, in order to minimize the chance that
ground-interaction problems will arise, pin
1 on each of the line output connectors is
isolated from all Model 47A circuitry and
ground points. “Floating” pin 1 virtually
eliminates the chance that a “ground-loop”
problem will occur.
2-Wire Party-Line Intercom
Connections
The Model 47A’s 2-wire party-line (PL)
intercom interfaces can be directly con-
nected with standard single- and 2-chan-
nel party-line intercom devices. But to take
advantage of the power that’s provided
on both pins 2 and 3 of the PL circuits, the
interfaces will typically be routed by way of
a source assignment panel (SAP).
The Model 47A can provide the DC power
required by connected intercom user devic-
es. The internal 30 volt DC intercom power
sources are limited to 315 mA of current.
This moderate amount of power requires
that the type and number of connected
user devices be selected appropriately.
Each of the two 2-channel PL interfaces is
also compatible with intercom circuits that
have their own DC power sources.
For convenience, the 2-wire PL intercom
circuits can be connected to the Model 47A
by way of four 3-pin male XLR connectors;
two are located on the back panel and two
on the front. They are organized in groups
of two connectors per interface—one on
the back and one on the front. They are
wired in parallel (“multed”) and provide
access to the identical signals.
Source Assignment Panel (SAP)
Applications
When used in conjunction with a broadcast
SAP installation the Model 47A should be
considered as having four independent
2-wire interfaces. Each interface should be
interconnected to the SAP such that com-
mon is on pin 1, DC with channel 1 audio
is on pin 2, and DC with channel 2 audio is
on pin 3. Typically the 2-wire PL XLR con-
nectors that are located on the Model 47A’s
back panel should be used. This will pro-
vide the most organized wiring implementa-
tion. In addition, the front-panel 2-wire PL
XLR connectors will remain available for
emergency and troubleshooting access.
2-Channel Intercom Systems
If direct compatibility with RTS TW systems
is desired the mating connectors (females)
should be wired so that common is on pin
1, DC with channel 1 audio is on pin 2, and
channel 2 audio is on pin 3. This wiring
scheme is correct whether the connected
devices are to be powered by an external
source or by means of the Model 47A’s
internal power sources.
Single-Channel Intercom Systems
There are two ways of connecting to the
Model 47A’s 2-wire PL intercom connec-
tors when compatibility with Clear-Com
single-channel intercom devices is desired.