Loewe Q2500B Serviceanleitung Seite 245

Technology of Q 2500 colour TV set
The Circle Surround Decoder operates with a
normal stereo signal. From this stereo signal
the decoder decodes the 6 sound channels.
This function has the advantage that for the
great majority of stereo transmitters a 5.1 sur-
round signal can already be used.
Dolby Pro Logic supports four sound chan-
nels.
2 channels for front left and right
1 centre channel
1 mono surround channel
Dolby Pro Logic also operates with a stereo
signal, this must, however, also be coded with
the Dolby Pro Logic standard. If this is not the
case then no Center/Surround Signal is pro-
duced.
NF bandwidth of the sound channels
Dolby
Pro
Logic
2 channels 20Hz-
Front L/R 20KHz
2 channels no
Surround
Mono 100-
Surround 7kHz
Center 20Hz-
7KHz
Deepsound- no
channel LFE
The AC 3 modules can receive digital audio
signals via three paths.
•
2
I S bus data supplied from MSP 341x on
the signal board.
•
SPDIF audio data from the two digital Au-
dio Cinch input sockets.
•
SPDIF audio data form the internal DVBi 2
Decoder (deliverable end 2002, not used
in all device variants).
The AC 3 module cannot process any ana-
logue sound signals directly. The analogue
Document Q 2500
Dolby Circle
Digital Surround
5.1
20Hz- 20Hz-
20KHz 20KHz
20Hz- 20Hz-
20KHz 20KHz
no no
20Hz- 20Hz-
20KHz 20KHz
20Hz- 20Hz-
100Hz 100Hz
sound signals from internal – e.g. Sat unit,
tuner or DB module – as also from external –
e.g. video recorder – sound signal sources,
must first be converted into digital sound bus
2
data (I S bus). This task is implemented by
the Multi Sound Processor MSP 341x, which
is incorporated into the signal board.
2
The digital I S bus data is emitted by MSP I
2051 on pins 4/5 and 6 and are fed to the AC
3 module via pins 5/6/7 of contact connector
W 2071. All analogue sound output signals to
the AV sockets and the headphones amplifier
are delivered by the MSP. The AC 3 module
has no influence on these output signals. The
AC 3 module does not deliver any I
data back to the MSP. This also means that
no sound signals are delivered to the AV
sockets and the headphones amplifier, if sig-
nals are supplied only via the SPDIF Cinch
sockets.
The SPDIF signals (SPDIF Sony Philips Digi-
tal InterFace, level 0.7 Vss-1 Vss to 75 Ohm)
are supplied by the Cinch sockets to the con-
tact strip W 2091 pin 14 SPDIF in1 and pin 11
SPDIF in2.
SPDIF data from DVBi 2 module is supplied to
W 2091 pin 10.
The SPDIF signals reach the AC 3 module on
changeover switch I 18. This is controlled by
2
the I C bus expander I 11 via pin 2/4. The
SPDIF signal selected for processing is output
to pin 7 of I 18. The selected signal is also
returned to the SPDIF Cinch outputs via pin
12 of Q 11 and W 301.
I 2 converts the SPDIF signal – input pin 42 –
2
of the I S bus data – I 2 pins 1/43/44 - from
2
MSP in the I S bus data for the I 1 (DSP -
Digital Sound Processor). I 1 processes this
audio data according to the prescribed stan-
dard. For this the respective software required
is loaded from I 5 memory. The memory is
organised into 8 blocks, each of 32 kByte. For
Circle Surround, Doby Pro Logic and Dolby
Digital a 32 kByte block respectively is re-
quired. If, for example, Circle Surround is
switched to Dolby Surround, the CCU controls
Expander I 11 via the I
that the address switching lines I 11 pin
9/10/11 of the memory block in I 5 for Dolby
Surround can be selected. DSP I 1 receives
an interrupt from CCU pin 77 via pin 14 of W
321.
122
2
S bus
2
C bus in such a way
© Loewe ProCollege