Dear Mr. Meyer,

I'm afraid there is no defined behaviour for the KM140s with only 30 V. And for testing, one would have to simulate the complete setup: not only the voltage, but also the current resources etc etc. In essence, it is a bit difficult to predict what happens with powering systems that simply do not follow the international standards.

The KM140s might work fine; the maximum level they can handle before distorting could be relevantly lower; the internal circuit might make strange noises when it doesn't get enough current; in the worst case a minimal mains power voltage change might happen during recording, causing the microphone to stop working...

Out of curiosity, and for my files: which preamp or console are you using, that provides only 30 V.

Best regards,
Martin Schneider / Neumann Mic. Development