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About Input cap and LC Filter

Hello, 

Could you please answer my question?

 

  1. The Left red square looks like LC filter. LC filter is needed in the output of audio amp, but why the LC filter is also needed in the power supply input?

  2. The left capacitor looks like tantalum capacitor, why it needs big capacitance polarity capacitor at the input power supply?

  3. On the Right red square, why it needed 3 each of different capacitor?