Mitsubishi Electric LT-2220 Service Manual page 27

2. Audio circuits
The audio circuits and speaker system of LT-22XX/LT30XX basically have the same circuits, except the Vcc
applied to the audio amplifier is different.
The specifications are as follows.
High Power (LT-22XX : 8W ,LT-30XX: 12W)
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2.1ch Sub woofer speaker system
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Impedance : 8 +/-1.2 ohms ( LT-22XX / LT-30XX )
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Compact and high performance sound enclosure box.
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Minimization of vibration noise
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Refer to the LT-22XX / LT-30XX Audio block diagram.
2-1 Audio input mixing circuits
The audio input block consist of 2 AV-SW, IC701(CXA2089) on SUB-PWB and IC100(CXA2069) on
MAIN-PWB. Audio inputs for VIDEO1 and VIDEO2 are connected to IC701. Other external audio Inputs
(Component1/2 and DVI and PC) are connected to IC100. Their output is connected to IC710 (Audio
Processor : MSP3440G ) of Scart1 / Scrat2 input port.
TV broadcasting audio(SIF) is also connected to IC710's IF Input port. Input sources are selected by register
control of IC 701/IC100/IC710 via 5V IIC-bus.
2-2 Audio processor IC
MSP3440G is used as the main audio processor.
This IC's functions are as follows.
De modulator (SAP/Stereo)
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Sub-woofer output
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Volume control
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Tone control
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Surround
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L/R mixing
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Audio line output
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Both models have the following audio controls on the users menu: Bass, Treble, Balance, Surround, Listen
to, Level Sound, Sub Woofer, Audio Out Fixed/Variable.
Audio adjustment of all controls except volume is performed by this IC.
(Refer to the "Owner's guide" for a full explanation of each control.)
2-3 Audio amplifiers and speakers
These models use 2pcs of 2-CH BTL type audio amplifier AN7522.
One piece is for main audio, and one more piece is for the sub-woofer.
Amplifier +B voltage and the input circuits are slightly different by model. ( Refer to table 1).
MODELS: LT-2220 / LT-2240 / LT-3020 / LT-3040 / LT-3050