But I found that the -VCC is quite unstable and this caused noise from speaker, which can hear even when music was played. And here is what my scope picked when nothing is played on computer from output (pin 6) of the Op Amp on the left.
And I picked the working frequency from pin 2 of ICL7660.
They lined up so nicely that's why I think it is the ICL7660 IC that caused the audible noise. Also, when music is played I found the -VCC become less negative significantly while VCC stays really stable.
So, can I improve this to get rid of that noise or must I make some other approach to fetch -VCC?