Studio Technologies 76DA V.3.01 - Manual (Page 10)

Issue 2, April 2011 Model 76DA/77 User Guide
Page 10 Studio Technologies, Inc.
for Surround
Digital Monitor Outputs
The 25-pin D-subminiature connector
labeled Digital Monitor Outputs provides
access to the Model 76DA’s 16 channels
of digital audio monitor output: pre-fader
surround, post-fader surround, post-fader
stereo, and stereo input C direct. The pre-
fader surround digital monitor output
channels are intended for connection to
metering or monitoring equipment that
requires uninterrupted full-level signals.
The post-fader surround digital monitor
output channels are intended to connect to
a 5.1 loudspeaker system. The post-fader
stereo digital monitor output is provided to
support a separate set of stereo monitor
loudspeakers.
The stereo input C direct digital monitor
output is essentially a unity gain copy of
the signal connected to stereo input C.
However, the signal does pass through the
sample rate conversion (SRC) and input de-
lay circuitry. The impact made by these func-
tions will depend on the specific input signal
and the Model 76DA’s configuration settings.
For flexibility the digital monitor outputs
are transformer-coupled and can be con-
figured to act as AES3 or AES3id digital
audio sources. The digital monitor outputs
are configured in two groups with separate
choices available for the pre-fader surround/
stereo input C direct group and post-fader
surround/post-fader stereo group. When
a group is set for AES3 (110 ohms/5 Vpp)
the signals are compatible with AES3 in-
terfaces. Signals of this type are normally
interconnected using shielded twisted-pair
cable terminated with 3-pin XLR connec-
tors. When a group is configured for AES3id
(75 ohms/1 Vpp) the source impedance and
signal level are compatible with the require-
ments of AES3id interfacing. These signals
are typically interconnected using coaxial
cable terminated with BNC connectors. For
details on how a Model 77 Control Console
is used to select the digital monitor output
types refer to the Configuration section of
this user guide.
A cable assembly with a 25-pin D-sub plug
(male) on one end and the desired con-
nectors on the other end will be used for
connecting to the digital monitor outputs.
The D-subminiature connector follows the
TASCAM® wiring convention, organizing
the 25 pins into eight groups of three pins
each; one pin remains unused. Each set of
three pins provides an independent inter-
face. In the analog world this would allow
eight audio signals to be transported. But
with AES3/AES3id digital audio signals
this allows support for 16 audio channels;
eight interfaces each supplying two audio
channels.
A wiring assembly prepared for the Model
76DA’s digital monitor outputs, when
configured for AES3 (110 ohms/5 Vpp),
would be identical to that of a DA-88-style
output assembly. An assembly of this type
would have a male 25-pin D-subminiature
connector (DB-25M) on one end and eight
3-pin male XLR connectors on the other.
A wiring assembly prepared for the Model
76DA’s digital monitor outputs, when set
for AES3id (75 ohms/1 Vpp), would typi-
cally have eight BNC plugs attached.
For compatibility with AES3 balanced
digital audio signals connect the D-sub’s
+ terminal as signal high and the – termi-
nal as signal low. In most applications a
3-pin XLR plug (male) will be used. In this
case the + terminal would go to pin 2 of
the XLR, the – terminal to XLR pin 3, and
the shield terminal to XLR pin 1.