Studio Technologies 76DA V.3.01 - Manual (Page 42)

Issue 2, April 2011 Model 76DA/77 User Guide
Page 42 Studio Technologies, Inc.
for Surround
timing reference (sync) signal and, if re-
quired, a configured value. If a word clock,
DARS (AES11), or AES3id signal is the
designated sync source its rate will be the
Model 76DA’s output sample rate. If a video
sync signal is connected, the Model 76DA’s
sample rate is selected as part of the con-
figuration process.
So in practice what can the SRC function
accomplish? If the output sample rate is
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 func-
tion 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 connect-
ed 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 loud-
speaker system. In addition, the stereo
input C direct digital 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 digital monitor output
to the input of a signal router, allowing 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
Central 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 asynchro-
nous, 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, receiving button and
rotary level control information and send-
ing 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 operat-
ing. You can disconnect the 9-pin intercon-
necting cable, move the unit (or units), and
then reconnect without issue. Upon discon-
nection 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 standard power-up
sequence and then normal operation will
resume.