Audio Base Band Processor; Loudspeaker Branch; Loudness; Sound Setting - Loewe Q2500B Serviceanleitung

Technology of Q 2500 colour TV set

5.2.6 Audio base band processor

In the DFP there is a pre-amplifier for all three
digital VF signal pairs; Nicam A/B, FM 1/2 and
Scart L/R. The adjustment of the pre-amplifier
for each VF input pair is independent and is
determined by the software. This means that
for further processing nearly the same digital
VF level is available.
For the FM 1/2 and Nicam A/B signal pairs the
pre-amplifier is followed by the necessary de-
emphasis. The FM 1/2 VF signal pair is fed
onward to the FM matrix. For an FM stereo
Audio Base Processor (DFP)
Mono
Scart / L
Scart / R
FM 1
FM 2
Nicam / A
Nicam / B

5.2.7 Loudspeaker branch

After channel selection the two VF channels
are led to the digital filter and control stages,
which are all controlled from the CCU via the
I²C bus. As the processing for both channels
is identical, the following description will deal
with one channel only.
5.2.8

Loudness

The signal comes from the matrix and is fed
initially to a filter with which an 'as heard'
loudspeaker control (Loudness) is imple-
mented. Depending on the loudspeaker set-
ting frequencies around 1 kHz are reduced, as
for same sound pressure the human ear
senses these frequencies as being a lot
Document Q 2500
Deem-
Matrix
phasis
Deem-
phasis
transmission the stereo L and R signals are
re-constituted from the L+R/2 signal of FM 1
and the R signal of FM 2 in the FM matrix.
The FM matrix is controlled by SDA 6000 via
the I²C bus according to the selected operat-
ing mode - stereo or mono. In the following
channel selection, after the selected operating
mode, the selected VF signal is switched to
the VF output branches in the MSP, which are
controlled independently of one another, for
loudspeaker, headphones and interface selec-
tion.
Loudspeaker branch
Bass
Treble
Matrix
Loudness
base width
Matrix
Headphones branch
Matrix Interface out.
louder than deeper or higher frequencies. The
filter coefficient necessary for the reduction is
determined and is applied in varying strengths
to the signal, depending on the volume.
5.2.9

Sound setting

The sound control stage consists of two sepa-
rate filters for the height and bass settings.
The control range for the two filters is +12 dB.
115
Volume
L
2x
R
D/A
Balance
Beeper
L
2x
R
D/A
L
2x
R
D/A
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