Panasonic EURO 4 Chassis, Техническое руководство

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24.5. Dolby Pro Logic Processing Path
The Dolby Pro Logic active processing as mentioned
earlier results in 4 channels being output in the form
of L/R/C and S, 5 channels for those models with
Super 3D Bass.
When this mode is selected the resultant audio
signals are output from
IC2401 via the following pins:
:
Front Left output via the I2S Bus
:
Front Right output via the I2S Bus
:
Centre pin 25
:
Surround pin 24
:
Super 3D Bass pin 27
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The front left and right signals output via the I
2
S bus
from IC2401 are fed back to the MSP IC2101 on the
E-Board.
Here the front left and right signals are processed for
bass, treble and volume before being output from the
MSP
IC2101 via pins 24 (R) and 25 (L). Here the right
and left audio signals are then fed to the audio output
IC
IC251 via buffer transistors Q2102 , Q2103 .
Where an external amplifier is connected then the
front left and right audio signals are output from pins
21 and 22 of
IC2401 and fed via buffer transistors
Q2409 , Q2410 to IC2402 pins 3 (L) and 5 (R) via
de-coupling capacitors C2434 and C2435.
Here the audio signals are amplified and buffered,
with the left audio signal being output via pin 1 and the
right audio signal output via pin 7. Both these audio
signals are then fed to the Audio monitor out terminal
JK2401 where the audio signals are then applied to
an external amplifier.
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To be able reproduce the centre channel (as well as
the processing already described), an additional
board, the C-Board is used. For those models without
the C-Board an external amplifier is required.
This centre signal which is output from pin 25 of
IC2401 is fed via a buffer transistor Q2401 , R2405.
Here at R2406 the centre signal is split into the
following paths.
:
Those models which can process the centre
signal internally without the use of an
external amplifier, feeds the centre signal to
the C-Board, which provides an internal
amplifier for the centre channel.
This centre channel which is fed to the
C-Board is fed via transistor
Q2425 , with two
muting transistors Q2424 and Q2432 in its
base.
The mute transistor
Q2432 which is
controlled by pin 4 of IC2401 (except UK
models) is used to mute the internal centre
channel when via the OSD display the
option Internal Speaker Off is selected. This
option is used to mute the centre channel
when an external amplifier for the centre
channel is used.
The centre channel which is fed to the
internal amplifier on the C-Board is fed to
connector K5 pin 3 and to connector C2 and
IC2703 (discussed in section 25.4.).
:
The centre signal which is to be output to an
external amplifier and for those models with
no C-Board, the centre channel is fed via
transistor
Q2402 where the centre signal is
input via pin 12 IC2402 .
Again the centre audio signal is amplified
and buffered before being output via pin 14,
from where the audio signal is fed to the
phono output terminal JK2401.