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3. Audio amplifying circuit
(1) Audio amplifying circuit is shown in the figure 3.2.2.3:
Figure 3.2.2.3 Audio amplifying circuit diagram
(2) Working principle: TDA7266P is a 3W+3W dual-bridge audio amplifying. Audio signals input
through pin 4, 12 of TDA7266 and then output from pin 1, 2, 14, 15 of TDA7266P after being amplified
by internal dual-bridge audio amplifier to drive loudspeaker to make sounds. This IC 10V power
supply, D122/D123 is drop diode and pin 7 is standby control pin. After machine enters power-on state,
pin 12 of cd4094 (AMP_STB) outputs high level and this IC enters working mode. This player adopts
default high level mode, so R22 is not used, but R28 is adopted to connect onto power. Pin 6 is mute and
controlled by mute circuit.
4. Mute control circuit
(1) Mute control circuit is shown in the figure 3.2.2.4:
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Figure 3.2.2.4 Mute circuit diagram
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