Circuit Descriptions and Abbreviation ListLC03E9.EN 91
9.8.1 IntroductionIn 'Virtual Dolby'-sets, the MSP has a separate Headphone
output so separate sound control is possible.
All sets contain one of ITT's Multistandard Sound Processing Mute control can be done in different ways:
ICs for sound decoding:- System muting. System muting is implemented for
MSP3410 (or 3411): Multi System (incl. NICAM) decoding ?special events? such as channel/source change event,
for Europe and AP (Virtual Dolby).loss of identification signal, on/off of set, during search
MSP3421 (or 3421): BTSC decoding for NAFTA and and auto store/program, sound mode change. This
LATAM (Virtual Dolby).muting is transparent to the user. Audio output should
be muted before the above ?special events? occurred,
This IC takes care of the main FM, AM and NICAM sound to prevent problems such as audible plop. Muting is
decoding. done via the SOUND-ENABLE line (active "low")
The analogue input and output sections of MSP offer wide connected to the amplifier-IC and coming from the
range of switching facilities such that it is possible to distribute Painter.
all possible source signals (internal and external) to the desired - Headphone status mute. A headphone status is
output channels (main, headphone or SCART outputs).available to detect the presence of the headphone and
All MSP versions contain digital audio processing, used for the mute the main speakers if the headphone is detected.
basic left/right stereo sound, such as bass, treble, balance, The microprocessor will read the HP-SIDE-DETECT
incredible sound and spatial and source selection (SIF-signal, status.
EXT1 or EXT2).- User muting. This is a mute option available to the
In addition to that, the MSP34x1 versions are also able to user. The user select the MUTE option on the remote
perform Virtual Dolby, a Dolby approved sound mode for control to switched off/on the sound output to the main
surround sound reproduction with left/right speakers only.loudspeaker and the subwoofer.
9.8.2 Source selectionAutomatic Volume Levelling (AVL)
One of the features of the MSP-family is AVL. If used, it limits
the big volume differences in the broadcast between e.g. news
Table 9-1 MSP overview
transmissions and commercials or within a movie.
To be able to get a Dolby approval (for the Virtual Dolby sets),
the AVL feature must be switchable. Therefore, the AVL Micronas ICSystemVirtual Dolby Region
MSP3410GMulti-system NoEurope/APfeature is customer switchable via the menu.
MSP3411GMulti-system YesEurope/AP
MSP3420GBTSCNoNafta/Latam9.8.5 Audio amplification (diagram A9)
MSP3421GBTSCYesNafta/Latam
Some specifications:
15? and 17? models: 2 x 3 W with power amplifier
The above-mentioned Micronas ICs are all having four pairs (L/
R) of SCART audio inputs. The fourth input pair (AV4) is used AN7522N.
23? models: 2 x 5 W with power amplifier AN5277N.
as audio-in (input cinches located at the Scaler board) for PC All models are equipped with a subwoofer output.
and HD modes.
To get a constant level output if the Tuner is selected, the The audio output stage is built around IC7731, which is a
SCART1 output (Tuner at any time) has to be fed back to the
input selector and selected as input for the MSP (SCART1 balanced amplifier, and is located on the TV board. It uses an
monolithic integrated power amplifier IC, the AN5277. The gain
input).of the amplifier is constant. This means that volume control has
to be done via the MSP.
9.8.3 Audio decodingThe supply voltage is 12 V/24 V depended on screen size,
generated by the power supply via L5733
At the input, a choice can be made between two IF-signals; SIF The AN5277 delivers an output of 2 x 10 W_RMS to two full
and SIFM.range speakers. A subwoofer is not implemented.
The selected signal is fed to the AGC. After this, an ADC
converts the IF-signal to digital.Headphone Amplifier
This digital signal can be processed by two demodulation The headphone outputs are from the same audio power
channels. The first one is able to handle FM and NICAM amplifier. The headphone jack will disconnect the audio output
signals. The second one can handle FM and AM signals.to the speakers when a headphone plug is inserted. Hence, the
Each channel contains a mixer to shift the incoming signal in speakers are muted if a headphone is connected.
the frequency domain. This shift is determined by the value of
a DCO (Digital Controlled Oscillator).
Protection
After the down-mix, the signal is fed, via a filter, to a This two resistors are to limit the audio output to HP.
discriminator. From here the AM, FM or NICAM demodulation
can be performed.9.8.6 Audio: Lip Sync
Both channels contain an 'automatic carrier mute' function,
which automatically mutes the output of the analogue section
when no carrier is detected.A ?lip sync? circuit with an 80 ms audio delay is added, in order
After demodulation, the FM-signals are subjected to a de-to synchronise with video delay due to the complexity of the
emphasis operation. After that, the matrix of the stereo system display processing. See table:
is applied.
9.8.4 Audio processing
The sound processing is completely done by the MSP34xx:
Volume control is done by the user via the SOUND menu.
Tone control in 'Stereo' sets is done via the BASS/
TREBLE control.
Headphone control in 'Stereo'-sets is done via the
loudspeaker output of the amplifier. |
ACEC
