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Phantom Power (and Microphone Interconnect Basics)

...................... From the "Ground" Up! By Eddie Ciletti
If youre new to the audio scene, lets start with a few basic electronic concepts then move on to Microphones and see how all of the connections are made, audio and phantom power.

Whats that you say? You dont know your AC from your DC? Audio is considered an Alternating Current, a.k.a. "AC." (So is 120-volt "wall" power.) But electronic circuits need Direct Current (DC) to turn them on, from batteries or power supplies. Like a speaker in reverse, a dynamic mic consists of a coil of wire suspended in a magnetic field. When vibrations move the cone or "diaphragm," the energy stored in the magnet is transferred to the wires. (A Dynamic mic is passive and needs no power.)

The preamplifier inside Vacuum Tube microphones requires both plate and filament voltages. Power and audio are delivered via special, multi-conductor cables and non-standard connectors from a dedicated power supply. Only then does the mic-level signal appear at a standard three-pin XLR connector. Transistorized microphones require much less power and can operate from a battery, hence the idea for phantom power, a system of distributing a DC voltage through a standard mic cable. All condenser mics (except electrets) requires a fairly large, but low current DC polarizing voltage that is applied to a diaphragm ? similar to a drum head, but thinner and plated with a molecularly thin conductive layer that is typically gold. The signal is not strong enough to venture into the outside world without an internal buffer / preamp (active electronics) that also requires power.

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Related Keywords:audio scene, electronic concepts, Alternating Current, magnetic field, diaphragm, Transistorized microphones, preamplifier, Vacuum Tube


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