Ok, 10000uf for testing is ok.
You have to cut the ground line and debug your circuit again.
Good luck!
I've marked the connections. Please take a look. The only ground in the output board is the power gnd from the snubber capacitor and the negative lead of the loudspeaker.
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your input groud is floating, there is no connection to the driver board and to the power supply ground, you can't do that, hum noise must there.
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Aaahhh 😀 At last found the source of the hum. 😀
The hum was due to the induction of the wires from the input board to the output board. I just separated them and the hum is gone ^_^