Studio Technologies 76 V.1.04 - Manual (Page 9)

Model 76/77 User Guide Issue 4, September 2008
Studio Technologies, Inc. Page 9
for Surround
located on the Model 76’s back panel.
Refer to Figure 2 for a detailed view of the
back panel. The BNC jacks will be used for
the digital audio signals. A cable assembly
with a 25-pin D-sub plug (male) on one
end and the desired connectors on the
other end will be used for connecting to
the analog monitor outputs.
Digital Audio Inputs
The nine female BNC connectors on the
Model 76’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 276M standard. As
expected, these signal sources will be
provided in the form of coaxial cables with
BNC plugs attached. The Model 76 sup-
ports sampling rates of up to 192 kHz with
a word length (depth) of up to 24 bits. Note
that no master external synchronization
source is required as each input is inde-
pendently self-clocking.
Balanced AES3 digital audio signals can
also be used with the Model 76’s inputs
so long as 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.
Monitor Outputs
The connector labeled Analog Monitor
Outputs provides access to the Model
76’s 6-channel (5.1) surround and
2-channel stereo analog monitor outputs.
The surround output channels are intend-
ed to connect to the main surround loud-
speaker system incorporated in a facility.
The stereo output allows support for a sec-
ondary set of stereo monitor loudspeakers.
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 op-
eration is preferred, unbalanced operation
does not pose a problem. To connect to
an unbalanced load connect the + terminal
as signal high, and both the – and shield
terminals 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 76’s electroni-
cally balanced output circuits are capable
of driving loads of 600 ohms or greater
the 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 76’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 Model 76’s
D-sub connector uses 4-40 threads. This
complies with the original design standard
for D-subminiature connectors.