DC-Bias

Most Capacitor microphones work by storing a static charge within the capacitive capsule. The traditional way of building up that static charge is by applying an external DC voltage, and this is known as a DC-Bias. Typically, the voltage is around 60VDC, but greater voltages permit more headroom, and altering the voltage can also vary the sensitivity of the capsule which is useful in configuring multi-pattern mics. The most common alternative to DC-Bias is the Electret design where the static charge is provided by a dielectric material built into the mic itself. A third alternative is the RF-bias technique which works on a different principle altogether.