Reducing Microphone Hum

Microphones and microphone cables are espefially sensitive to hum picpup because of the great amplification needed for microphone level signals (few millivolts). The hummign can be caused to microphone signals because of ground loops and because of induced noise. Here are some tips to minimize microphone hum pickup:

• Use low impedance microphones (150-6000 ohms). All modern recording equipments and mixers are designed to work with low impedance microphones.
• Use microphones with balanced outputs (three pin XLR connectors). Thus kind of microphones pick up less hum than unbalanced microphones.
• Routinely check microphone cables to make sure that the shield is connected at both ends.
• Check that the screw near the XLR connector on the microphone is securely screwed in place inside microphone handle.
• Do not connect the ground on XLR connectors to the shell of the connector, because ground loop hum may occur if a grounded shell touches a metallic surface.
• Do not ground microphone juction boxes or snake boxes except through the cable shield.