Help for understanding a Chinese U87 fake microphone schematics

[sunsplash]

Hello everyone,
I would need someone to help me understand the attached schematic.
I am discovering the microphone DIY and comparing with other schematics, this one seems very complicated.
I took a lot of care for the reverse engineering and I think there is no mistake.

Thank you for your help

 

[OneRoomStudio]

It doesn't seem all that complicated, but it's definitely not a U87. The lower section generates the polarizing voltage (60V) from 15V. The two FETs are in a darlington configuration to lower the output impedance since there's no output transformer to step things down. The BC547B and BC557B drive the output, and probably further reduce the output impedance. It's definitely a little unusual, but if you have to design to hit a low price point (as many Chinese engineers are asked to do), you have to jump through some hoops. An output transformer could have made this circuit much simpler, but that costs money...