Dear Mr. Lewis,

I'll mail you the schematics of SM and power supplies. The differences are in the capsule polarization voltages (80V vs. 120V). The NSM2 has a voltage divider, where in the case of the SM23 it's in the microphone. So, an NSM23 might kill an SM2 capsule!

Best regards,
Martin Schneider / Neumann Mic. Development