EN 50
3139 785 3093x
8.
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 HEF4052 which is a dual four-to-one
multiplexer and MSP3415G which is a multi-sound processor.
a) Scart 1 – Output path
The multiplexer [7303] 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 [7900]
for performance reasons (noise reduction, jitter, …) and
transformer (level correction, ground isolation,…) to the digital
out cinch socket at the rear.
d) Record path
The record-selector [7302] 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.
8.2.6. Audio ADC/DAC
The conversion of analog audio signals from the record-
selector [7302] outputs (ALADC/ARADC) is done via
UDA1361TS [7704]. This IC can process input signals up to
2Vrms 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 [7703]. 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.
Muting for the various other output lines are done via AKILL
& BKILL-lines which is a combination of the D_KILL from
the Digital board and POWER_FAIL from power supply and
AMUTE & BMUTE (digital silence mute) from DAC-part.
