Digital Audio Corporation PCAP II, User Manual

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3
1.2 External Processor Capability
The PCAP II
EXTERNAL PROCESSOR unit is a high-performance,
self-contained digital signal processor and contains 27 DSP
microprocessors, which are allocated as follows:
•
Sixteen FIR filter processors which can be configured as 1, 2,
3, or 4 independent audio processors. These flexible
processors may be combined into mono and stereo
configurations. Any of the processors may be configured as
an adaptive or adjustable digital filter.
•
Two FIR fixed filter processors which are dedicated as output
spectral equalizers.
•
Two FIR fixed filter processors which perform interpolation
and decimation filters.
•
Four FIR fixed filter processors which perform input and
output highpass filters.
•
Three general-purpose microprocessors which execute
special DSP software, implement the dual FFT spectrum
analyzer, communicate with the PC via RS232, and provide
system control.
Analog-to-digital and digital-to-analog conversion is performed by
stereo, 16-bit, sigma-delta converters which perform 64x
oversampling.
The base sample rate is adjustable from 7.2 kHz (3.2 kHz bandwidth)
to 36 kHz (16 kHz bandwidth). All sample rates are exact multiples
of 50 Hz and 60 Hz, allowing maximum filter performance at
harmonics of these frequencies.
Digital, 200Hz highpass filters are provided on all inputs (pre-process)
and on all outputs (post-process) to remove rumble and other low-
frequency noises.
Microprocessor-controlled limiters are provided on both analog inputs
to prevent overload. When using the S/PDIF digital inputs, the
limiters prevent the digital signal from exceeding a specified level.