Dsp Circuit; Power Supply - Orban OPTIMOD 8400 Operating Manual

6-12
TECHNICAL DATA

DSP Circuit

Power Supply

consisting of opamps IC3A and IC3B, followed by high-current buffers IC1 and
IC2, which are inside the feedback loops of IC3A and IC3B.
The two SCA inputs are summed into IC3B and IC3A. These therefore are not in-
dicated on the Composite Level meter displayed by the 8400, because this meter
indicates only the composite signal generated by the DSP.
The composite line driver amplifiers are socketed for easy field replacement; all
other components are surface-mounted and are not field-replaceable.
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 8400 and can
occur abnormally if the 8400's watchdog timer forces the Elan to reboot. Upon initializa-
tion, the Elan CPU downloads the DSP executable code stored in the disk-on-chip mem-
ory. This typically takes about 40 seconds. Once a DSP chip begins executing its pro-
gram, execution is continuous. The Elan provides the DSP program with parameter data
(representing information like the settings of various processing controls), and extracts
the front panel metering data from the DSP chips.
During system initialization, the Elan queries the DSP hardware about its operational
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 Customer Service.
The DSP chips are located on the DSP board, which is identifiable by the small toroidal
inductor, L700, which is mounted on it—see Figure 6-1 on page 6-22. This board con-
tains a local switching regulator that reduces the "raw" 10 volts from the power supply
module to 3.3V for the DSP chips. Because of the danger of damaging the DSP chips, we
do not recommend that this regulator be repaired in the field.
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
8400. 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 also feeds local regulators.
Orban Model 8400