SERVICE MANUAL FOR M35&36; CHASSIS

TCL
Chassis M35&36 Service Manual
1.2.5. Manual Mode
Below Fig. shows the source channel assignment of demodulated signals in case of manual mode.
1.3. Preprocessing for SCART and I 2 S Input Signals
The SCART and I 2 S inputs need only be adjusted in level by means of the SCART and I 2 S prescale registers.
1.4. Source Selection and Output Channel Matrix
The Source Selector makes it possible to distribute all source signals (one of the demodulator source channels
or SCART) to the desired output channels (loudspeaker, etc.). All input and output signals can be processed
simultaneously. Each source channel is identified by a unique source address.
For each output channel, the sound mode can be set to sound A, sound B, stereo, or mono by means of the
output channel matrix. If Automatic Sound Select is on, the output channel matrix can stay fixed to stereo
(transparent) for demodulated signals.
1.5. Audio Baseband Processing
1.5.1. Automatic Volume Correction (AVC)
Different sound sources (e.g. terrestrial channels, SAT channels, or SCART) fairly often do not have the same
volume level. Advertisements during movies usually have a higher volume level than the movie itself. This
results in annoying volume changes. The AVC solves this problem by equalizing the volume level. To prevent
clipping, the AVC’s gain decreases quickly in dynamic boost conditions. To suppress oscillation effects, the gain
increases rather slowly for low level inputs. The decay time is programmable by means of the AVC register . For
input signals ranging from .24 dBr to 0 dBr, the AVC maintains a fixed output level of .18 dBr. Below Fig. shows
the AVC output level versus its input level. For prescale and volume registers set to 0 dB, a level of 0 dBr
corresponds to full scale input/output. This is
– SCART input/output 0 dBr = 2.0 Vrms
– Loudspeaker output 0 dBr = 1.4 Vrms
1.5.2. Loudspeaker Outputs
The following baseband features are
implemented in the loudspeaker output
channels: bass/treble, loudness, balance,
and volume. A square wave beeper can
be added to the loudspeaker channel.
1.5.3. Quasi-Peak Detector
Simplified AVC characteristics
The quasi-peak readout register can be used to readout the quasi-peak level of any input source. The feature
is based on following filter time constants:
attack time: 1.3 ms
30 03.Mar.2003