Studio Technologies 76DA V.3.01 - Manual (Page 41)

Model 76DA/77 User Guide Issue 2, April 2011
Studio Technologies, Inc. Page 41
for Surround
monitor outputs. A power-down circuit sup-
plies the main microcontroller integrated
circuit with an indication that a power loss
is imminent. When this condition is detect-
ed the digital monitor outputs will switch to
silence (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 change of signal transients
reaching the connected 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
messages 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 76d
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
communication 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 error
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 connected
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 engineers at Stu-
dio Technologies came up with a unique
and exotic circuit to perform this function it’s
really not the case. Several semiconductor
companies provide “single-chip” SRC solu-
tions and an excellent one from AKM was
selected for the Model 76DA. The technical
capabilities of the Model 76DA’s SRC func-
tion is stated in this way: the sample rate
of an input signal can range from 1/6 to
six times the Model 76DA’s output sample
rate, with the additional restriction that it
must be no less than 8 kHz and no more
than 216 kHz. The Model 76DA’s output
sample rate is determined by the selected