Studio Technologies 76DA V.4.02 - Manual (Page 47)

Model 76DA/77 User Guide Issue 4, March 2013
Studio Technologies, Inc. Page 47
for Surround
48 kHz then a signal connected to stereo
input C can have a sample rate from 8 to
216 kHz. Or, as another example, if the
Model 76DA’s output sample rate is 96
kHz a signal connected to stereo input C
can have its sample rate range from 16
to 216 kHz.
As useful as allowing one disparate
sample rate to be converted to another,
it may be the ability of the Model 76DA’s
SRC function to re-synchronize a signal
that proves most valuable. For example,
in typical post-production and broadcast
applications all signals will have a sample
rate of 48 kHz. A Model 76DA and all of its
normally connected input signals will be
“locked” to the main timing reference signal
that supports the 48 kHz sampling rate.
But, as an example, a signal associated
with a portable device, while at a 48 kHz
sampling rate, may not be synchronized
(“genlocked”) to the “house” reference.
Connecting this signal to stereo input C will
cause the SRC function to “lock” it to the
Model 76DA’s rate, thus allowing it to be
monitored over a loudspeaker system. In
addition, the stereo input C direct monitor
output can be connected to other devices
that find need for the now-synchronized
signal. In some cases it may be useful to
connect the stereo input C direct monitor
output to the input of a signal router, allow-
ing an entire facility to access the signal.
Model 76DA to Control
Console Connections
Figure 7 gives a detailed description of the
signals that connect the Model 76DA Cen-
tral Controller to the one or more Model
77 or Model 71 Control Consoles. The
Model 76DA provides a +12 volt DC power
source for use by the control console’s
circuitry. The DC output is current-limited
to minimize the chance that a short-circuit
condition will damage the Model 76DA’s
circuitry. An asynchronous, bi-directional
data interface links the connected units.
The RS-485 hardware connection scheme
operates at a rate of 115.2 kbit/s and uses
an 8-N-1 data format. The Model 76DA
communicates with each Model 77 and
Model 71 unit 20 times per second, receiv-
ing button and rotary level control informa-
tion and sending LED and 4-digit display
status data.
“Hot” Disconnection of
Control Consoles
There’s no problem relocating one or
more Model 77 or Model 71 Control
Consoles while the StudioComm system
is operating. You can disconnect the 9-pin
interconnecting cable, move the unit (or
units), and then reconnect without issue.
Upon disconnection of all control consoles
the Model 76DA Central Controller will
mute the internal digital audio channels
as well as saving the current operating
parameters. No clicks, pops, or other
noises will occur when the Model 77 or
Model 71 units are again connected. The
control consoles will go through their stan-
dard power-up sequence and then normal
operation will resume.
Channel Status, User, and
Validity Bits
The non-audio bits that are part of the
AES3/AES3id digital audio monitor output
channel data are actively controlled by
the Model 76DA’s software. The Chan-
nel Status bits use the Professional Use
of Channel Status block. They indicate a
word length of 24 and the current sample