How to convert a PC desk mic into a directional electrect?

[fjpompeo]

Converting a PC desk mic

Hi,

Need to convert my electrect PC desk microphone into a directional electrect PC desk microphone in order to reduce pickup of enviroment noise like PC PSU and or PC CPU fan, street noise and so on. If possible with automatic level control (compressor/limiter).

This mic will be used in a HAM 80m SSB station.

Regards,

Fernando

 

[Buriedcode]

Re: Converting a PC desk mic

Hi,

As far as I know, the only way to change a omni electret mic into a unidirectional one (cardiod) you must change the mic element, ie: the electret part itself. These are available from a number of sources, I recently purchased many from 'farnell.com', they have many different sizes and models of both unidirecitonal,. and omni.

Unfortunately, I can't test them with my soundcard, because its mic input was blown a while back (totally my fault), but with a preamp and line in, all the electret elements I got from farnell were very good qaulity.

If you can't get hold of any replacement elements, there is one method I know of. The only difference between omnidirecitonal, and unidirectional mics is that, uni's have holes in the back of the element. This means that any sound coming from behind the mic hits the back of the diaphram AND the front (because it goes through the holes and around the inside of the element). So, because the sound wave hits both the front and back at the same time, it cancels it out. I've yet to turn an element into a uni with this method, its trickly and you might end up ruining it.

Hope this helps.

BuriedCode.

 

[fjpompeo]

Re: Converting a PC desk mic

BuriedCode,

Tks for the reply. I'll try to get some directional electrect mic from an electronics supply store here in my town and will pay a close attention of this detail (holes in front and back) just to meka sure I'm buing the right mic.

73,

Fernando - PU2PLL - Brazil