Dsp Circuit; Power Supply - Orban Optimod-FM 8300 Operating Manual

6-12
TECHNICAL DATA

DSP Circuit

Power Supply

The DSP circuit consists of eight Motorola DSP56362 24-bit fixed-point DSP chips that
execute DSP software code to implement digital signal processing algorithms.
The algorithms filter, compress, and limit the audio signal. The eight DSP chips, each
operating at approximately 100 million instructions per second (MIPS), for a total of
800MIPS, provide the necessary signal processing. A sampling rate of 32 kHz and
power-of-two multiples thereof, up to 512 kHz, is used.
System initialization normally occurs when power is first applied to the 8300 and can
occur abnormally if the 8300's watchdog timer forces the SC520 to reboot. Upon ini-
tialization, the SC520 CPU downloads the DSP executable code stored in the flash
memory. This typically takes about 7 seconds. Once a DSP chip begins executing its
program, execution is continuous. The SC520 provides the DSP program with pa-
rameter data (representing information like the settings of various processing con-
trols), and extracts the front panel metering data from the DSP chips.
During system initialization, the SC520 queries the DSP hardware about its opera-
tional status and will display an error message on-screen if the DSP fails to initialize
normally. Please note any such messages and be ready to report them to Orban Cus-
tomer Service.
The DSP chips are located on the DSP board — see the drawings starting on page 6-
52. IC703 is a local voltage regulator on the DSP board that derives the +3.3V supply
for the DSP chips from the +RAW unregulated system voltage.
Warning! Hazardous voltages are present in the power supply when it is connected
to the AC line.
The power supply converts an AC line voltage input to various power sources used
by the 8300. To ensure lowest possible noise, four linear regulators provide 15VDC
and 5VDC for the analog circuits. A switching regulator provides high current
+5VDC for the digital circuits. An unregulated voltage powers the fan and feeds lo-
cal regulators.
The power supply circuits are straightforward and no explanation is required be-
yond the schematic itself. Be aware that C1, C4, C5, and C12 in the switching regula-
tor are premium-quality low-ESR capacitors and must be replaced with equivalent
types to ensure proper operation of the switching supply.
The output of the power supply is monitored by the power-indicator LED circuit,
which causes the power LED to flash according to a preset code to diagnose prob-
lems with the various power supplies in the 8300. See step (2.B) on page 4-8.
ORBAN MODEL 8300