Studio Technologies 76D V.2.02 - Manual (Page 10)

Issue 2, June 2009 Model 76D/77 User Guide
Page 10 Studio Technologies, Inc.
for Surround
input C direct 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 delay circuitry. The impact
made by these functions will depend on the
specific input signal and the Model 76D’s
configuration settings.
It’s important to reiterate that all the monitor
outputs are digital; the Model 76D doesn’t
provide any analog outputs! This requires
that all equipment connected to the Model
76D’s monitor outputs provide digital input
capability.
For flexibility the monitor outputs are
transformer-coupled and can be configured
to act as AES3 or AES3id digital audio
sources. The monitor outputs are configured
as groups with separate choices available
for the pre-fader surround/stereo input C
direct group and post-fader surround/post-
fader stereo monitor output group. When a
group is set for AES3 (110 ohms/5 Vpp) the
signals are compatible with AES3 interfaces.
Signals of this type are normally intercon-
nected using 3-pin XLR connectors. When
a group is configured for AES3id (75 ohms/
1 Vpp) the source impedance and signal
level are compatible with the requirements
of AES3id interfacing. These signals are
typically interconnected using BNC connec-
tors. For details on how a Model 77 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 interface.
In the analog world this would allow eight
audio signals to be transported. But with
AES3/AES3id digital audio signals this al-
lows support for 16 audio channels; eight
interfaces each consisting of two audio
channels.
A wiring assembly prepared for the Model
76D’s 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 con-
nector (DB-25M) on one end and eight
3-pin male XLR connectors on the other.
A wiring assembly prepared for the Model
76D’s digital monitor outputs, when set for
AES3id (75 ohms/1 Vpp), would typically
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 + signal would go to pin 2 of the
XLR, the – terminal to XLR pin 3, and the
shield terminal to XLR pin 1.
For compatibility with AES3id unbalanced
digital audio signals connect the D-sub’s
+ terminal as signal high, and both the
– and shield terminals as the signal low/
shield. When terminating to a BNC plug
the D-sub’s + terminal should connect to
the center pin; the – and the shield con-
nections should go to the “body” of the
BNC plug. For optimal operation, it is best
to connect both – and shield together di-
rectly on the D-sub plug, rather than at
the BNC end of the interface assembly.
Note that the output circuitry is transform-
er-coupled so it is possible to just connect