Alternatively, you may prefer to build an M/S mic using a PCB rather than stripboard...
Hobby microphone builder Mic Scharf has developed a PCB for this version of the project,
which you can obtain from: HERE
The schematic above shows the circuitry required to interface 3 x 'FETless' electret microphone capsules with a microphone pre-amplifier, to provide a 'Mid/Side' style stereo microphone in a single BM800 style enclosure
The microphone is used in conjunction with a 2 channel microphone preamplifer, which must include the capability of supplying 48v phantom power to the circuitry.
This 'Mid/Side' application uses a OPA1642 dual op-amp, with each of the amplifiers providing a separate audio output for both the MID and SIDE channels. Each channel includes only 2 resistors in each signal path. This helps to minimise any noise generated by the circuitry, and should allow for microphone with a self noise level of only around 5dBA to be created.
As the application here uses FETless electret capsules, there is no need to generate any polarisation voltage to bias the capsules.