"Dave Plowman (News)" wrote in message
...
In article ,
Arfa Daily wrote:

"Dave Plowman (News)" wrote in message
...
In article ,
Arfa Daily wrote:
I've never found them to be particularly heat sensitive within common
sense limits, but note that they are polarity sensitive, as they
contain a FET preamp which is phantom powered via the output terminal
...

A few electret mic are phantom powered but the majority use a form of
AB power for the capsule.


I'm using the term "phantom powered" loosely Dave, in that the audio out
is floating on the DC in, because there are only two connections, one
of which is the FET drain terminal, the series DC 'feed' resistor
therefore actually being the drain load resistor. The other terminal
(also the capsule case) is of course ground or FET source. Where there
is this type of power / signal setup, it is often considered
generically, to be 'phantom powered' ... Excuse my ignorance, but
what's "AB power" ?

Not a good idea to use it where mics are concerned, though. Can cause
confusion.

Other thing is not all electrets have the same ground polarity. But
hopefully are marked.

AB or T power is where the DC is fed up the audio pair on a balanced mic.
Dates from before true phantom and has the disadvantage it puts DC across
a moving coil mic - although when it was common many used a PS for each
mic, rather than getting it from the mixer.


OK, but seems that all of this is tending to look at 'whole' mics as in
something that a newsreader would clip to himself, whereas the original
poster was talking about just the capsule inside, which was also what I was
referring to. As far as the polarity of electret mics varying, I can't
remember ever seeing a capsule where the case wasn't a negative-side ground,
and over the years, I have dealt with and replaced many in cordless phones
and similar.

I appreciate that to a sound engineer, the term "phantom power" has a
slightly special meaning in terms of voltage level etc, but that still
doesn't change the fact that generically, any system where DC power is
supplied to an active signal source, using only the wires that are carrying
the signal rather than any additional power carrying wire, are considered to
be 'phantom' powered, irrespective of the voltage involved. TV antenna
amplifiers for instance, are often described as being phantom powered, as
also are satellite LNBs.

However, all that said, I do take your point that it could give rise to
confusion between a sound engineer reading it, and an electronics engineer,
who might better understand the overall concept. Perhaps it would be better
to call the electret capsule 'line powered' ...

Arfa