Studio Technologies 76B 2008 - Manual (Page 10)

Issue 1, July 2008 Model 76B/77B User Guide
Page 10 Studio Technologies, Inc.
for Surround
confi guration function doesn’t allow this
anyway so there is no potential for a
problem to develop.) Also, the left and
right channels of stereo input C can’t be
independently monitored by way of the
auxiliary output. It follows a left-in-to-left-
out, right-in-to-right-out scheme.
The nine female BNC connectors on the
Model 76B’s back panel are used to inter-
face with digital audio signal sources. Each
of the digital audio inputs is intended for
connection to an unbalanced digital audio
source that is compatible with the AES3id-
2001 standard. In broadcast environments
these signals may also be referred to as
following the SMPTE 276BM standard.
As expected, these signal sources will
be provided in the form of coaxial cables
with BNC plugs attached. The Model 76B
supports sampling rates of up to 192 kHz
with a word length (depth) of up to 24 bits.
Note that no master external synchroniza-
tion source is required as each input is
independently self-clocking.
Balanced AES3 digital audio signals
can also be used with the Model 76B’s
inputs if external coupling transformers
(“baluns”) are utilized. These impedance-
matching (110 ohms to 75 ohms) trans-
former assemblies typically provide a 3-pin
female XLR connector on their input and
a female BNC connector on their output.
Analog Monitor Outputs
The connector labeled Analog Monitor
Outputs provides access to the Model
76B’s surround (5.1) and stereo (2-chan-
nel) auxiliary monitor outputs. The sur-
round output channels are intended to
connect to the main loudspeaker system
incorporated in a facility. The auxiliary
output channels are provided to support a
separate set of loudspeakers, the primary
application intended to allow monitoring of
inter- or intra-facility communications.
The monitor output channels are designed
for connection to audio amplifi ers associ-
ated with monitor loudspeakers, or to the
inputs of loudspeakers that contain inte-
grated amplifi ers. The monitor outputs are
electronically balanced and capable of
driving balanced or unbalanced loads
of 600 ohms or greater. While balanced
operation is preferred, unbalanced opera-
tion does not pose a problem. To connect
to an unbalanced load connect the
+ terminal as signal high, and both the
– and shield as the signal low/shield. For
optimal unbalanced operation, it is impor-
tant to connect both – and shield together
directly on the D-sub plug, not at the other
end of the harness.
Note that while the Model 76B’s electroni-
cally balanced output circuits are capable
of driving loads of 600 ohms or greater
their output level will drop slightly as the
load impedance approaches 600 ohms.
A 0.5 dB difference in output level can be
expected as the load impedance changes
from 10 k ohms to 600 ohms.
The wiring scheme used by the D-sub-
miniature connector complies with that
made popular by TASCAM® with their
DA-88® product. A wiring assembly pre-
pared for the Model 76B’s monitor outputs
is identical to that of a DA-88-style output
assembly. Please refer to Figure 4 for the
exact connection details. Note that unlike
a DA-88-style assembly, the two threaded
fasteners associated with the Model 76B’s
D-sub connector uses 4-40 threads. This
complies with the original design standard
for D-subminiature connectors.