Professional condenser microphones require a 48-V supply to charge the internal capacitive transducer and power the internal buffer for the high-impedance transducer output. You can use a simple boost converter, a filter circuit to reduce electromagnetic interference (EMI), and a little trickery to build a compact, ultra-low-noise, phantom power supply (48 V) that operates from a 5-, 12-, or 24-V input. This voltage is often provided by what’s called a “phantom” supply arrangement, which uses the existing microphone connections to deliver power, so no additional supply leads are needed.
(Note that the condenser microphone should not be confused with the electret microphone, which sometimes employs a phantom-power source but of a different kind for its internal preamplifier. If you’re not familiar with the principle and application of phantom power for condenser microphones, see the References at the end for various perspectives.)