BSS Audio Prosys PS-8810, User Manual

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PS-8810
DIGITAL SIGNAL PROCESSOR
Technical Description
Following is a technical description of the operation of the BSS PS-
8810.
Input Section
Each audio input signal first passes through a balanced filter
designed to eliminate RF interference. The RF filters are a
balanced network of chokes, ferrite beads, and capacitors that
attenuate both common-mode and differential-mode signals
above 500 kHz. Optional input isolation transformers are
available.
The balanced signal then enters the input switching circuit. This
circuit can insert a 25dB pad for line level signals or apply
phantom power to the input terminals (24VDC through two 2
Kohm resistors). The signal is filtered again to eliminate lower-
frequency RF energy such as interference from the AM broadcast
band.
A discrete preamp stage takes the balanced input signal and
provides 13 to 45 dB of voltage gain adjustable by a rear panel
potentiometer. The preamp output provides a single-ended
voltage output that is then coupled to a single-ended-to-
differential amplifier that also provides the bias offset needed by
the A/D converter.
A 24-bit high-resolution A/D converter samples the input audio at
48 kHz. The audio processing is set to p20dBu as full
scale, allowing full utilization of the dynamic range of the
converter. Each converter supplies a two-channel digital audio
stream to the DSPs for processing. One A/D converter acts as a
master to supply sampling clocks to the rest of the system. A
12.288 MHz oscillator (256 times the 48 kHz sampling rate) acts
as the master clock source.
DSP Processing Section
Four DSP processors supply all of the digital audio processing in
the unit. Serial digital audio from the input converters is sent to
the DSP board for processing. Digital audio from either the Input
board or the CobraNet board is routed to the two input DSPs.
The processors collect 16 samples of audio, then process the
18.0 Technical Information
Audio