EN 143
3139 785 31150
9.
Circuit- and IC description
The sound processing is always done in stereo (that means
separate left- and right- channel) and the complete switching
is realized by using HEF4052B which is a dual four-to-one
multiplexer and MSP3415G which is a multi-sound processor.
a) Scart 1 – Output path
The multiplexer [7301] selects either signals from the Scart
2 Input (AIN2L/AIN2R) or the Audio DAC (ALDAC/ARDAC) as
the output source for Scart 1 (AOUT1L/AOUT1R).
b) Scart 2 – Output path
The MSP [7500] selects either signals from the Scart 1
Input (AIN1L/AIN1R), the Audio DAC (ALDAC/ARDAC) or the
Tuner Frontend as the output source for Scart 2 (AOUT2L/
AOUT2R).
c) Digital audio-out path
In addition, a digital output (DAOUT) coming from the
Digital board is passed through a 6-fold inverter [7700] for
performance reasons (noise reduction, jitter, …) as digital
Audio / Optical outputs at the rear.
d) Record path
The record-selector [7300] selects either signals from the
Scart 1 Input (AIN1L/AIN1R), Scart 2 Input (AIN2L/AIN2R),
Front Cinch (AINFL/AINFR) or the MSP (AFEL/AFER) and
routes to the audio ADC (ALADC/ARADC) for record
purposes. The switch is controlled via RSA1 and RSA2
signals coming from the MSP.
9.3.7. Audio
ADC/DAC
The conversion of analog audio signals from the record-
selector [7300] outputs (ALADC/ARADC) is done via
UDA1361TS [7803]. This IC can process input signals up to
2V
rms
by using external resistors in series to the input pins.
All required clock signals are generated on the digital board
and only the audio data (A_DAT-line) are routed to Digital
board for further processing.
The transformation of digital audio back into analog domain
is done by CS4351 [7802]. All necessary clock signals are
coming from the digital board and digital audio data
(D_DATA0-line) are converted into analog signals (pin 15 and
18). The output signals from the audio DAC part (ALDAC/
ARDAC) are directly routed to the rear cinch sockets. To
avoid plops and any other audible noise on the output muting
circuits are implemented for each channel.
9.3.8. Muting
Muting for the various outputs (Scart 1, Scart 2 and rear
Cinch sockets) are done via the AKILL, BKILL and AMUTE
& BMUTE (digital silence mute) lines which is a combination
of the D_KILL from the Digital board, IMUTE from the
Slave
μ
P and IPFAIL from power supply
