Behringer T1953 manual Phantom power, Dynamic range of various media

TUBE ULTRAGAIN T1953

dB
100
75
50					DigitalTape(16Bit)	AnalogMixingConsole
25	FMRadio	AnalogRecords	AnalogTape	CompactDisc
VideoTape

Fig. 4.8: Dynamic range of various media

4.9 Phantom power

Condenser microphones need a specific supply voltage polarizing the condenser diaphragm. This voltage can be furnished from an internal battery, or an external power supply that is either connected directly to the microphone or supplies the voltage through the microphone cable. In practice, this technique is usually referred to as +48 V or phantom power supply, and uses the microphone cable to carry both the audio signal and the supply voltage required for the microphone.

Please read this chapter thoroughly: phantom power can damage the microphone, if used improperly.

Fig. 4.9: Functional diagram of phantom power supply

We speak of phantom power when a microphone cable is used to carry several signals, with a DC voltage “layered” on the actual audio signal. The typical phantom DC voltage is +48 V, which is applied both to the positive (pin 2) and negative inputs (pin 3) of the XLR connector, using current-limiting resistors. As the phantom voltage is split up in a balanced configuration among the signal leads, there is no need to apply it directly to the microphone transducer or the microphone itself, where it could damage the transducer and/or capsule. In an unbalanced configuration, DC voltage would be applied directly, which would inevitably lead to disturbing noise or could even damage the electronics.

4. TECHNICAL BACKGROUND 19