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>5.2.11 DAC5.2.10 Loudspeaker control and AVC(Automatic Volume Control)The signal then passes through the loudspeakercontrol stage. The control rangecomprises 64 stages. In MSP 3411 eachchannel has a second control stage for thebalance <strong>set</strong>ting.In addition, the MSP <strong>of</strong>fers the facility <strong>of</strong>measuring the level at the input. This is usedas the AVC function. This means that it ispossible to select different volumes for transmittersduring breaks for advertisements orbetween different transmitters. Therefore, thedesign does not provide for a programme locationrelated volume correction.The actual value on the input determined bythe MSP is communicated to SDA 6000 viathe I 2 C bus. In the operating s<strong>of</strong>tware a preciselydefined amplification is assigned via thevolume value. If the measured value deviatesfrom the required value, the volume is decreasedor increased via the I 2 C bus until therequired value is reached.VF leveltransmitterBreak foradvertisementsA DAC is controlled with the signal <strong>set</strong> by thedigital controller. The analogue signal is outputfor the right and left channels on pin27/28. The signal is then fed via transistors Q2081 and Q 2083, which are switched as animpedance converter. Via the coupling capacitorsC 2082/84 the signal then arrives at W1610, pins 1 and 2, and from there is fed tothe basic board on the two output stages.5.2.12 Headphone branchIn the headphone branch there is an independentvolume <strong>set</strong>ting, that can be changedindependently <strong>of</strong> the loudspeaker volume,also in 64 stages.The digital/analogue converted audio signalsfor the headphones are output to pins 24/25.The W 1494 audio Cinch sockets are suppliedwith level by pins 36/37 <strong>of</strong> the MSP. In orderto deliver sufficient output level to these Cinchsockets the Q <strong>2500</strong> chassis has in this branchtwo amplifier stages, consisting <strong>of</strong> the operationalamplifier I 2091C and D. The amplifiersamplify the signal by a factor <strong>of</strong> 2. For the <strong>set</strong>ting“Sound via HiFi unit“ the output level canbe <strong>set</strong> from 0 Vss to 3.5 Vss.If “Sound via <strong>TV</strong>“ is <strong>set</strong>, then there is a standardlevel on the Cinch sockets.VF leveloutputMSP30-70msca 10sThis means that various control constants areused. Loud passages are toned down within30 to 70 ms. An increase in s<strong>of</strong>t passages onthe other hand occurs with a delay <strong>of</strong> about 10s, to avoid an unwanted increase in volumeduring the transmission. In addition, the AVCcan be switched <strong>of</strong>f within the sound menu.5.2.13 Interface branchThe audio level for the interface is <strong>set</strong> by theoperating s<strong>of</strong>tware and cannot be changed.The digital, analogue-converted VF signals forthe interface connection are applied to pins33/34.5.2.14 Deadline volumeDuring operation, a kind <strong>of</strong> awakening functioncan be programmed into the Q <strong>2500</strong> chassisas a deadline time. In addition, there is anawakening tone, with an adjustable volume.Document Q <strong>2500</strong> 116 © Loewe ProCollege
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