3.2.1 Signal processing board
1. Input selection circuit
AV321T(RU) has6 kinds of input means in all: optical input, coaxial input, CD, DVD, 5.1CH and
tuning input. Digital signals of optical, coaxial input of this player are directly sent to power amplifier
board for processing through flat cable. Analog input selection of AV321T(RU) is fulfilled through an
electronic switch Cd4052 (N101) and its truth value table is shown as the following:
Section Two Unit Circuit Principle
AV321T (RU) has 3 kinds of input states: tuning, VCD , DVD, and they are controlled through 4052-
A, 4052-B signal respectively (refer to truth value for details). Signals after being gated output from pin 3
and pin 13 of N101, and then output left/right main channel signal from its pin1, 12 through N111 CD
4052 to decode board for signal processing.
Analog signal input in 5.1 state: the gating of 5.1 analog signal input of AV321T(RU)is controlled by
two IC CD 4053 (N102,N103), control pin 9,10,11 of CD 4053 are all controlled by the 5.1CH signal
outputted from pin 4 of M62446(N104), when 5.1CH signal is high level, the gating is analog signal input
of 5.1 state; in this state, there is no digital sound field, all signals are straight through; when 5.1CHis
low level, the gating is the synthesized signal after decoding.
Straight through and digital sound field switch control: AV321T (RU) has two different modes of
straight through and digital sound field, and its gating input is controlled by N111/CD4052 and N102/CD.
When control signal 4053-INT is high level, for it is connected to the enabled end of N102, this IC is in
non working state, main channel signals output through pin 5, 11 of N111 and directly send to M62446
for processing to output Hi-Fi musical signals. When 4053-INT is low level, main channel signals are
sent to decode board for digital sound field processing through Xp17, and N102 is also in working state.
2. Karaoke signal processing circuit
For karaoke signals sent from MIC base board, after coupling and amplifying, one path is sent to
volume and tone adjustment IC PT 2315 (N203) for processing, then after echo and delay adjustment
状态
引脚
VCD
DVD
A
1
0
1
B
1
1
0
Tuning
Estate
PIN
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