Some professional condenser microphones are designed to accommodate an internal battery, while others require phantom power from the microphone mixer or a phantom power supply. The microphones supplied with most computers often operate on bias voltage supplied by the sound card through the Ring portion of the stereo miniplug connector. So far, computer audio inputs cannot provide the phantom power used by many professional condenser microphones.

Connecting The Mic To The Sound Card
To connect a professional low Z dynamic microphone (or a condenser mic with internal battery power) with a three pin XLR output connector to the 3.5 mm miniplug mic input of a computer, a special cable must be purchased or made.

For the microphone to work properly, the cable must have the proper type of connector for the computer input (usually three conductor ‘stereo’ miniplug) and be wired correctly. The correct wiring scheme depends on the computer’s microphone input. Cable wiring for the most common computer connectors is illustrated below.

Wiring diagram for dynamic microphone to sound card with mono miniplug

For computers with a stereo mini plug mic input connector: The wires that are connected to pins 1 and 3 of the XLR connector should both be connected to the Sleeve of the stereo miniplug. The wire that is connected to pin 2 of the XLR should be connected to the Tip of the miniplug. No connection should be made to the Ring of the miniplug, because dynamic microphones do not require external dc power.

Wiring diagram for dynamic microphone to sound card with stereo miniplug

Sometimes it is impossible to tell if the connector on a computer is of the mono or stereo variety. If a cable that is equipped with a mono connector is plugged into an audio input that uses a stereo connector, the microphone should still work. This is because the Ring portion of the input jack will make contact with the Sleeve portion of the miniplug on the mic cable, which will connect any dc bias voltage to ground.

Connecting Pro Condenser Mics
Connecting a professional condenser microphone to a computer can be complicated, because there are so many variations between different brands of microphones in terms of bias voltage requirements. (Phantom power is a defined audio industry standard and is usually the same regardless of the brand, but no sound cards are able to provide it.) Here are the possible situations:

- If the microphone can operate on an internal battery, no external source of power is needed and the mic can be connected to the computer using the same wiring scheme as for a dynamic type.