Studio Technologies 76DA V.4.00 - Manual (Page 44)

Issue 3, July 2012 Model 76DA/77 User Guide
Page 44 Studio Technologies, Inc.
for Surround
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.
Power-Up Messages and
Error Codes
Upon mains power being applied to the
Model 76DA all connected Model 77 units
will go through a power-up sequence.
The sequence starts by each of the indi-
vidual LEDs lighting in a “walk-through”
sequence. Then the 4-digit display tests all
its LED segments. Finally, a set of mes-
sages provide details on the specific Model
77 and connected Model 76DA software
versions:
1. Displays 77
2. Displays Model 77’s software version
3. Displays Model 77’s unit address
(A1, A2, A3, or A4)
4. Displays 76DA
5. Displays Model 76DA’s main software
version
6. Displays FPgA
7. Displays Model 76DA’s logic device
(FPGA) software version
After a successful system power-up
sequence normal operation will then com-
mence. Should a problem be encountered
during power up one of two error codes
may show on the Model 77’s 4-digit display.
If Err1 displays it indicates that communi-
cation is not taking place with the Model
76DA. The most likely cause would be
incorrect wiring of the data pair linking the
two units. Err2 indicates that the Model
76DA is having problems with its internal
logic device. (A high-speed field-program-
mable gate array (FPGA) serves as the
digital “heart” of the Model 76DA and with-
out it no audio activity can occur.) The only
way to remedy this condition is to first try
removing and reconnecting mains power.
(And that’s a long-shot as to whether it
would accomplish anything.) If the error
code continues to be displayed the Model
76DA must be returned to the factory for
service. Note that for the vast majority of
StudioComm systems neither of these er-
ror codes, especially Err2, will ever appear.
Sample Rate Conversion
(SRC)
Circuitry associated with stereo input C
can provide sample rate conversion (SRC)
capability. A digital audio signal con-
nected to that input can have its sample
rate and timing re-synchronized to match
the Model 76DA’s internal timing. While
it would be nice to proclaim that the en-
gineers at Studio Technologies came up
with a unique and exotic circuit to perform