[iyonix-support] Re: Voice recording

  • From: Jeremy Nicoll - freelists <jn.flists.73@xxxxxxxxxxxxxxxxxxxx>
  • To: iyonix-support@xxxxxxxxxxxxx
  • Date: Mon, 18 Jun 2007 21:02:49 +0100

tennant@xxxxxxxxxxxxxxxxx (Tennant Stuart) wrote:

> What's an electret?

Many 'studio'-quality mics work by having the vibrating air (which sound
causes when passing through air) move very fine plates of a capacitor.  The
effect of a varying distance between capacitor plates changes the effective
capacitance of that capacitor and - when it is in a circuit - means there
are small changes in the current in that circuit.

Those very small current changes are amplified, first (often) by a small
amplifier built-in to the mic, and later by amplifiers in the mixing desk
(or whatever else the mic is connected to).

Such a microphone needs power both for its inbuilt amplifier and to set up
the charge in the capacitor circuitry.  Such capacitor (or 'condenser') mics
tend to be very sensitive and accurate, and are the sort of mics used for,
for example, recording delicate nuances in classical music.  Mics like this
are usually expensive (costing hundreds or even thousands of pounds each).


Electret technology replaces the externally powered capacitor with a
substance which is manufactured holding a charge. They are less fragile than
real capacitor mics.  The power on an electret capsule is often supplied by
just a single battery.  These are very much cheaper!  There are some
'studio'-grade mics made with this technology, but in general this is the
other extreme. 

-- 
Jeremy Nicoll - my opinions are my own

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