[sdiy] Low noise electret condenser microphone amp?

[Bert Schiettecatte]

Hi List,

I've got a couple of panasonic microphone cardridges here
(omnidirectional). They have some sort of preamp but I've found that I
still need to amplify them by a factor of roughly 200x before they will
pick up my voice from a reasonable distance (about 40cm). I built a
simple amplifier circuit I found on the net, based on an LM324 op-amp.
When I run the circuit by itself from a power supply it seems to work
fine, but it also amplifies a lot of noise. When I include the circuit
into a bigger microcontroller circuit I've been working on, I get even
more noise that is amplified by the 200x gain opamp. Any ideas on where
I can find a really good microphone amplifier circuit? It should be able
to pick up sound 40cm away and amplify it to a reasonable level. 

Thanks,
Bert