Output Circuits - Orban OPTIMOD 6300 Operating Manual

OPTIMOD 6300 DIGITAL

Output Circuits

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) and out-
put sample rate converter (SRC). 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 con-
nectors with a low impedance balanced output. The digital output transmitter ac-
cepts the digital audio words from the output sample rate converter (SRC) and
transmits them as AES3-format digital audio signals on the digital output connector.
1. Stereo Digital-to-Analog (D/A) Converter
Located on input/output/DSP 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 48 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/DSP 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
IC211. The purpose of these stages is to reduce the out-of-band noise energy
resulting from the delta-sigma D/A's noise-shaping filter and to translate the
differential output of the D/A converter into single-ended form. These com-
ponents apply a 3
This filter does not induce significant overshoot of the processed audio, which
would otherwise waste modulation.
IC212 and associated components form a low-frequency servo amplifier to re-
move residual DC from the signal. The 0.1Hz
induced overshoot in the processed audio.
The buffered output of IC201 is applied to IC213, a balanced output line
driver. This driver emulates a floating transformer; its differential output level
is independent of whether one side of its output is floating or grounded.
IC213 and its right channel counterpart IC214 are socketed for easy field re-
placement. All other circuitry is surface-mounted.
The corresponding right channel circuitry is functionally identical to that just
described.
rd
order low-pass filter to the differential signal from the D/A.

3 dB frequency prevents tilt-
6-9
TECHNICAL DATA
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