A circuit model for a microphone?

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#23
bubbamc119 said:
EC8010: I should have listened to you the first time!



Can we keep this on topic please? I will be adding to this thread as I progress.
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Hi bubbamc119
With who way we can you help more beyond? You do not write if you have constructed some circuit for your microphone from that i see. It would serve you a theoretical analysis of my preamplifier? Perhaps some measurements with oscilloscope? Unfortunately and me i do not have some Real Time Analyzer except from the sound card of my P.C. and some FFT softwares. It should you know however that even if my sound card it is a S.B. X-Fi Platinum which is considered enough good, my direct measurements showed that it has enough high TIM. The same is in effect (believes) with any other sound card as long as expensive it is. And this is owed in the A/D converter. Personally i do not entrust the sound cards for precision measurements.
Regards
Fotios
 
#25
Finally I cannot understand where this thread goes. It began with a question of bubbamc119 for a mic preamplifier, we proposed various constructions in the practice, and as i believe it has resulted in an exclusively theoretical and philological discussion; for what? Also I see that some people they try construct the preamplifier that I proposed. What I have to point out is that; the construction of an electronic circuit it requires from equal theoretical and practical knowledge. It is impossible you achieve what you have theoretically calculated in a practical circuit if you do not know certain basic things. For example, i prefer always the gnd of signal it is independent from electric gnd. Many times the ready cables of microphones that are sold in the market they have linked the signal gnd with the metal jacket of XLR plug. This is unacceptable. For this it should not us touches the panic and we begin the questions before we examine with each attention - alone us – everything that passes from our hand. Also all the microphone inputs are very sensitive as they have very large gain. It is mandatory a careful shielding. Summarising, i use this preamplifier for electro acoustic measurements with the application “Speaker Workshop” and be very reliable in measurements with Behringer ECM8000. I quote below two measurements of the mic. preamplifier - by alone - to prove its reliability. And the measurements have been taken by the oscilloscope and not by sound card based software.

Output noise with open input and powered by 18Vdc with input gain and level controls at full. It is only 5,6mVrms.

An externally hosted image should be here but it was not working when we last tested it.


Transient response under square wave of 10KHz in input. The bounces are very little and well dumped for a so dificult signal managed by NE5532 old operational amplifiers. And the rise time it is very succesful at 3,1ìsec.

An externally hosted image should be here but it was not working when we last tested it.


Regards
Fotios
 
#27
Well guys I ended up partially designing a low noise on board condenser mic pre for my thesis.

The design starts from first principles, modelling the microphone and designing a low noise stage to suit the requirements exactly.

I thought it prove interesting to some of you guys so here it is;
http://www.megaupload.com/?d=HNWXK6YN

Unfortunately there's not much electronics jobs here in Perth so I'm working as an electrical engineer instead.
 
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