OSA MP-1A OPAMP

[kmozart]

The soldering job seems a bit dirty and there's also a lot of links there, I don't know if those were to correct some mistakes in the pcb traces.

That is why I am in a search of the schematic.

 

[Whoops]

That is why I am in a search of the schematic.

You will probably not find an OSA schematic, but the circuit should is so simple and similar to the API 312 circuit.
So you can print the API 312 schematic and trace your preamp using that schematic as a base