Technology of Q 2500 colour TV set
Technology of Q 2500 colour TV set
Technology of Q 2500 colour TV set
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<strong>Technology</strong> <strong>of</strong> Q <strong>2500</strong> <strong>colour</strong> <strong>TV</strong> <strong>set</strong>5.2.1 Audio baseband processing− Flexible selection <strong>of</strong> the sound source to beprocessed, e.g. demodulator or Scartsocket− Selectable de-emphasis− Pre-amplifier for Nicam/FM and Scart signal− Independent volume adjustment for loudspeakerand headphones− Adjustment <strong>of</strong> bass, level, loudness,stereoscopic sound and balance in theloudspeaker branch and virtual surround− Stereo matrixDemodulator/Decoder blockQPSKDecoderNicamDecoderNicam / ANicam / BIntercarriersignalfromtunerIF signalfrom SAT tunerIF1IF2IF channel 2AGC A / DOscillatormixerFilterDemodulatorStereoZweitonDetectionStereoDetectionRegisterFM 2to audio base band processor (DFB)IF channel 1OszillatorMischerFilterDemodulatorFM 15.2.2 Demodulator/decoder blockThe sound/IF inter-carrier signal output by thetuner passes via a band-pass consisting <strong>of</strong>L/C 2032, R/C 2033 and C 2036, to thesound/IF input1, pin 67 <strong>of</strong> MSP 3411. Theband-pass suppresses frequency componentsbelow 4.5 MHz and above 10 MHz. In this waysound interference that could be caused bythe <strong>colour</strong> carrier or the neighbouring picturecarrier is prevented. If the Twin-SAT unit isused a SAT sound/IF reaches the sound/IFinput2 on pin 69 <strong>of</strong> MSP via pin connector W1416 /pin 4 and the band-pass, consisting <strong>of</strong>L/C 2037, R/C 2038 and C 2009.The analogue sound/IF signal is passed internallyfrom pin 67 (Hyperband tuner) or 69(SAT unit) to a transfer switch that is able toswitch between the two IF inputs <strong>of</strong> the MSPunder s<strong>of</strong>tware control. The analogue IF signalis then adapted optimally by an automaticamplifier control, which can control input signalsfrom 0.14 to 3 Vss, to the ADC. The ADCchanges the sound/IF signal into an 8-bit datastream. The sampling rate is 18.432 MHz.This is produced by the internal clock generator.The frequency determining 18.432 MHzquartz is connected to pins 71/72 <strong>of</strong> MSP3411. This 18.432 MHz clock is also used forall digital processes in the MSP.The digital sound/IF signal is now processedin a multi-standard sound processor by twoindependently operating sound/IF channels.This is necessary, for example, in order toprocess stereo transmissions with carrier fre-Document Q <strong>2500</strong> 113 © Loewe ProCollege
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