Roll your own microphone

not capacitive but:

Mic, PSU, XLR cable, accessories and carry case for US$188.

.... Phil

Search for a "condenser microphone".

Made in Santa Cruz CA:

Do-it-thyself: Plenty to choose from.

Have fun...

Why not use the capacitance variation to modulate an RF oscillator frequency? The s/n would be outrageous.

-- Jeff Liebermann snipped-for-privacy@cruzio.com

Sennheiser MKH and probably others work like that

Broadcast quality? Like BBC newsreaders use? What type of mic out of the many variants available gives the best fidelity in this kind of application where voice reproduction quality is key?

They have a fixed frequency oscillator and the mic capacitance variation detunes the FM demodulator, which achieves essentially the same effect.

The fixed frequency come from a crystal oscillator (for low FM noise).

I found this out when I reverse engineered a Sennheiser MKH 816T microphone back in the '80s. Someone had asked me to fix it, but it turned out that that it wasn't broken at all; they were just using the wrong sort of phantom supply. (I ended up building a crude phantom supply out of a 7812 regulator and a 1:1 audio transformer. It worked adequately well.)

Regards, Allan

The dynamic range of dynamic mic is about 135dB.

The dynamic range of a good, DC biased condenser mic is even better.

Condenser mics using FM were tried, but soon abandoned for a variation using AM instead - cos the latter were much quieter.

Even so, DC biased types dominate the market by a huge factor.

Sometimes the simplest idea is the best.

.... Phil

That standard has dropped quite a lot in recent years... microphone quality is comprimised by visual appearance.

This is most noticable when the commonly used revers microphone breaks down and the audio technician quickly hands a classic microphone to be used instead. The difference in audio quality is really staggering.

No idea what you mean by "revers" and "classic" microphones.

Outrageous good, or outrageous bad? I was thinking of doing that, actually.

Good, I think.

I think that, for good s/n, a little diaphragm motion should steer a lot of power. So a chunky RF oscillator might do that.

I guess any good microphone will ultimately be limited by vibration and Brownian motion. I think a bigger diaphragm is better as regards Brownian noise. Maybe a ribbon mic with capacitive, rather than magnetic sensing? Has that been done?

There are probably few applications that need a really low-noise microphone. There will usually be a lot of ambient noise.

In the case of small electret mics used in hearing aids about half the noise comes from brownian motion of the air molecules and half from the FET amplifier.

Especially subsonic noise. Omni-directional electret mics often have small holes laser-punched in the diaphragm to provide a well defined low frequenct leak. Otherwise the mic output saturates when doors are closed.

John

Classic mic probably refers to something mounted on a stand, likely a true condenser with Cardioid pattern. The result is quite different, more low end and less ambience so "intimate" sounding.

.... Phil

Very cool. Synchronous rectification in 1963.

In message , Lasse Langwadt Christensen writes

There seems to have been an interest in electrostactic acoustid device some time ago.

Not quite a microphone, but it will work in reverse.

and

preamp design

Brian

I built myself a pair of those when I was at school. They sounded very good, but I got fed up with getting electric shocks because of my poorly constructed housing.

John