[sdiy] trying to understand amplification of an electret mic element

[dan snazelle]

On Sep 6, 2011, at 2:58 PM, Ingo Debus wrote:

> 
> Am 06.09.2011 um 17:15 schrieb dan snazelle:
> 
>> normally when I want to add a lot of gain to something quickly, I grab a TL072 and use a resistor combination of say 1k to 1M.
>> 
>> However, with these microphone elements, things are all weird.
>> 
>> I started off as I understand you are supposed to by connecting the element to a 9v source through a 1k resistor. i tied the other end to ground. I took the signal out through a .1uf cap.
> 
> So you connected the mic through a 0.1 uF cap to a preamp with an input impedance of 1k? The cap is way too low then, try 10 uF.
> 
> Ingo



SUCESS


switching the cap to a 10uf as Ingo suggested, and using an  inverting instead of non-inverting  amplifier made a WORLD of difference.

I can now get giant gains with just one opamp.


Can anyone explain this difference?  Does it have something to do with an impedance mis-match? Or too little/too much filtering?

I am going to get out my Walter Jung books and read up on mic preamps 


thanks for everyones advice!


it all helped


now I just need to understand why it is working.


thanks!