OPTIMOD-AM DIGITAL TECHNICAL DATA
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3. Digital Input Receiver and Sample Rate Converter (SRC)
Located on Input/Output board
The integrated receiver and input sample rate converter, IC500, accepts digital
audio signals using the AES3 interface format (AES3-1992). The built-in sample
rate converter (SRC) accepts and sample-rate converts any of the “standard” 32
kHz, 44.1 kHz, 48 kHz, 88.2 kHz, and 96 kHz rates in addition to any digital audio
sample rate within the range of 32 kHz and 96 kHz. The SRC converts the input
sample rate to 64 kHz. The final, high-quality decimation to the 9400 system
sample rate is done in the system DSP, as was done for the analog input.
This chip is surface-mounted and not field-replaceable.
Output Circuits
The 9400 has two stereo pairs of analog outputs and two AES3 digital outputs. We
will describe Output #1; Output #2 is identical except for its component reference
designators.
This circuitry interfaces the DSP to the analog and digital audio outputs. The digital
audio from the DSP is transmitted to the digital-to-analog converter (D/A) or output
sample rate converter (SRC) associated with a given output. The digital-to-analog
(D/A) converter converts the digital audio words generated by the DSP to analog
audio. The analog output stages scale and buffer the D/A output signal to drive the
analog output XLR connectors with a low impedance balanced output. The digital
output transmitter accepts the digital audio words from the output sample rate
converter (SRC) and transmits them to the digital output connector via an AES3 out-
put formatter and driver chip.
1. Stereo Digital-to-Analog (D/A) Converter
Located on input/output board
The D/A, IC211, is a stereo, 24-bit delta-sigma converter. It receives the serial left
and right audio data samples from the DSP at 64 kHz sample rate, and converts
them into audio signals requiring further, relatively undemanding analog filter-
ing. IC211 is surface-mounted and is not field-replaceable.
2. Analog Output Stages
Located on Input/Output board
The left and right analog signals emerging from IC211 are each filtered, ampli-
fied, and applied to a floating-balanced integrated line driver, which has a 50
output impedance. The line driver outputs are applied to the RF-filtered left and
right analog output connectors. These analog signals can represent either the
transmitter or monitor output of audio processing.
Component-Level Description:
IC201 and associated components filter the left channel signal emerging from
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