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The manual for my 702 says to use a "plug in power" mic, not a regular mic,
or else damage may occur. What constitutes a "plug in power" mic.
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A "plug-in-power" mic is the consumer-friendly name for a "phantom-powered"
electret condenser microphone. Unlike dynamic microphones which generate the
current representing the sound by use of a moving magnet or coil assembly
(the inverse of the common loudspeaker), the electret condenser microphone
uses a capacitor that varies its capacitance value according to the sound
that it picks up. Therefore it can't generate its own voltage and needs an
"exciter voltage" to be presented in order to make a useable signal.
Previously this current was supplied by a small 1.5 volt battery if the
microphone was a handheld type. Or, in the case of devuces that had the
microphone built into them such as video cameras, telephones, apartment
entryphone systems and most portable cassette recorders made since 1970, the
device's circuit provided the "exciter voltage" to the microphone part.
As far as standalone microphones were concerned, manufacturers realised that
people were having headaches with flat batteries and non-working condenser
micrphoones and began to develop the concept of "line-power". This is very
similar to the TV masthead amplifiers which had the amplification circuitry
attached to the antenna and the signal being passed through a power supply
box that was located indoors, next to the TV set. The power supply box would
inject a low-voltage current upstream to the masthead amplifier which would
return a boosted TV signal. Also it is similar to how the power supply at
the telephone exchange provides power to the ordinary telephone's
electronics at all times irrespective of the mains power that comes to your
home.
By applying this to electret-condenser microphones, this problem was solved
and it was applied initially to professional-use microphones and
"direct-inject" boxes. Then Sony started to introduce it into their
camcorders, audio tape recorders and selected high-end video recorders in
order to achieve this goal. This also allowed affordable microphones to be
so small that they can he hidden -- a useful tool for "stealthing" a
concert. They used the term "plug-in-power" to brand this concept of
"phantom power" or "line power" in a consumer-friendly way.
With regards,
Simon Mackay
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