Studio Technologies 76D V.2.02 - Manual (Page 9)

Model 76D/77 User Guide Issue 2, June 2009
Studio Technologies, Inc. Page 9
for Surround
Audio Connections
Audio connections are made by way of nine
BNC jacks and a 25-pin D-subminiature
connector. All the connectors are located
on the Model 76D’s back panel. Refer to
Figure 2 for a detailed view of the back
panel.
Audio Inputs
Two surround (5.1) and three stereo
(2-channel) digital audio sources can be
connected. All sources can be monitored
using the pre- and post-fader surround and
post-fader stereo monitor output channels.
A one-to-one relationship is maintained
between the input channels and output
channels, i.e., left input to left monitor out-
put, right input to right monitor output,
center input to center monitor output, etc.
(Of course this won’t be true in the case
where the user has enabled the 5.1 to
stereo downmix function.) Stereo input C
is also routed to the stereo input C direct
monitor output.
The audio inputs support digital audio sig-
nals with sampling rates of up to 192 kHz
and a word length (depth) of up to 24 bits.
However, all the connected signal sources
must maintain a common sample rate and
timing reference. Having all signals “locked”
together ensures proper handling by the
Model 76D’s all-digital signal path.
There is, however, an exception worth not-
ing. Circuitry associated with stereo input C
has sample rate conversion (SRC) capabil-
ity, allowing virtually any digital audio signal
to be connected. Refer to the Technical
Notes section of this guide for a detailed
review of the SRC capability. A signal con-
nected to stereo input C can have an inde-
pendent sample rate and timing reference
and still be monitored correctly.
Nine BNC jacks (female) on the Model
76D’s back panel are used to interface with
the 18 channels associated with the digital
audio signal sources; each BNC connec-
tor carries two audio channels. The digital
audio inputs are intended for connection
with unbalanced digital audio sources that
are compatible with the AES3id standard.
In broadcast or post-production environ-
ments these signals may also be referred
to as following the SMPTE 276M standard.
This signal type has a nominal impedance
of 75 ohms with a nominal signal level of
1 Vpp. As expected, these digital audio
sources should be provided in the form of
coaxial cables with BNC plugs attached.
Balanced AES3 digital audio signals
can also be used with the Model 76D’s
inputs if external coupling transformers
(“baluns”) are utilized. These impedance-
matching (110 ohms to 75 ohms) and
level-attenuation transformer assemblies
typically provide a 3-pin female XLR con-
nector on their input and a female BNC
connector on their output.
Monitor Outputs
The 25-pin D-subminiature connector
labeled Digital Monitor Outputs provides
access to the Model 76D’s 16 channels
of digital audio: pre-fader surround, post-
fader surround, post-fader stereo, and
stereo input C direct monitor outputs. The
pre-fader surround monitor output chan-
nels are intended for connection to meter-
ing or monitoring equipment that requires
uninterrupted full-level signals. The post-
fader surround monitor output channels
are intended to connect to the main 5.1
loudspeaker system incorporated in a facil-
ity. The post-fader stereo monitor output
is provided to support a separate set of
stereo monitor loudspeakers. The stereo