Studio Technologies 76DA V.4.02 - Manual (Page 45)

Model 76DA/77 User Guide Issue 4, March 2013
Studio Technologies, Inc. Page 45
for Surround
Reference Level
The reference level button sets the post-
fader surround and stereo monitor output
levels to their preset values. The operat-
ing characteristics are identical to those of
the Model 77 Control Console, discussed
earlier in this section.
Technical Notes
Loss of Sync
The Model 76DA relies on an external
timing reference (sync) source for proper
operation. This can be in the form of an
AES3id, word clock, DRS (AES11), bi-level
video, or tri-level video reference signal.
In most cases the sync signal will be con-
nected to the sync input BNC connector
located on the Model 76DA’s back panel.
Alternately, a configuration choice allows
the L/R input of the AES3id source cur-
rently selected for monitoring to also serve
as the system’s timing reference. When-
ever a valid sync signal has been con-
nected to the Model 76DA the sync status
LED, located on the unit’s front panel, will
light. The sample rate of the monitor output
channels will reflect the rate of the sync
input and, if a video sync source is utilized,
the configured rate.
If a valid sync signal is not present sev-
eral visual indications are provided. On
the Model 76DA the sync status LED will
flash. On all connected Model 77 Con-
trol Consoles the 4-digit LED display will
cease normal operation, instead alternat-
ing between the words no and sync. When
a valid sync signal is again connected
the Model 76DA’s sync status LED will
light steadily. On the Model 77 units the
word sync will momentarily be displayed
followed by a brief display of the monitor
output sample rate. The sample rate will
display as 32.0, 44.1, 48.0, 88.2, 96.0,
176.4, or 192.0, reflecting the impact of the
sync source rate and the Model 76DA’s
configuration.
If during normal operation the sync source
changes from one valid rate to another a
visual indication is provided. On the Model
77 units the new sample rate—32.0, 44.1,
48.0, 88.2, 96.0, 176.4, or 192.0—will
momentarily be displayed.
Any time that a valid sync signal is not
connected to the Model 76DA the monitor
outputs will automatically revert to an inter-
nally generated sample rate of 48 kHz with
no digital audio content present. This audio
“black” signal will allow most connected
equipment to continue to function correctly,
of course with no meaningful audio signal
present. As soon as a valid sync signal is
again connected to the Model 76DA the
monitor outputs will automatically switch to
their correct sample rate and audio signals
will again be present.
Power Down
Great care was taken in the Model 76DA’s
design to minimize the chance that clicks,
pops, or other objectionable audio signals
will be present on the post-fader digital
and analog monitor outputs. A power-down
circuit supplies the main microcontroller
integrated circuit with an indication that a
power loss is imminent. When this condi-
tion is detected the digital monitor outputs
will switch to silence (digital audio “black”)
in preparation for a complete loss of signal.
Electromechanical relays associated with
the analog monitor outputs will change to
their mute state to minimize the chance of
signal transients reaching the connected
loudspeaker inputs.