Electret Condenser Microphone Preamp

Thread Starter

Vipul Kumar 1

Joined Oct 20, 2018
79
Can anyone suggest me a good high quality ,close to no noise,No distortion,No humming,No buzzing,No ground loop and Very Sensitive PreAmp Circuit for Electret Condenser Microphone????
 

Thread Starter

Vipul Kumar 1

Joined Oct 20, 2018
79
Hello,

I hope that this thread will not become like your other thread:
DIY PreAmp Ground Noise/Loop/Hum/Buzz/Distortion

The circuits posted are well known and tested.
You can even buy PCB's for the circuits on that site.

Bertus
in my city components are not available easily so that is why i wanted a good circuit simulator software Sir so that i can simulate the circuit before a make one pls suggest me one good circuit simulator software
 

bertus

Joined Apr 5, 2008
21,439
Hello,

Why do you have two pots in your schematic (R8 and R9)?
Pot R8 will distroy the DC requirements of Q2.
Also R10 will have no effect.

Did you ever have a look at the schematics I posted earlier and in your other thread?

Bertus
 

Thread Starter

Vipul Kumar 1

Joined Oct 20, 2018
79
yes i hv seen Sir previous schematic but the schematic i posted all components are available with me
Bertus Sir should i remove R8 and R10
 

Thread Starter

Vipul Kumar 1

Joined Oct 20, 2018
79

bertus

Joined Apr 5, 2008
21,439
Hello,

The calculations are given quite direct:

Collector-Feedback Bias

Variations in bias due to temperature and beta may be reduced by moving the VBB end of the base-bias resistor to the collector as in Figure below. If the emitter current were to increase, the voltage drop across RC increases, decreasing VC, decreasing IB fed back to the base. This, in turn, decreases the emitter current, correcting the original increase.

Write a KVL equation about the loop containing the battery, RC , RB , and the VBE drop. Substitute IC≅IE and IB≅IE/β. Solving for IE yields the IE CFB-bias equation. Solving for IB yields the IB CFB-bias equation.





Collector-feedback bias.


Find the required collector feedback bias resistor for an emitter current of 1 mA, a 4.7K collector load resistor, and a transistor with β=100 . Find the collector voltage VC. It should be approximately midway between VCC and ground.





The closest standard value to the 460k collector feedback bias resistor is 470k. Find the emitter current IE with the 470 K resistor. Recalculate the emitter current for a transistor with β=100 and β=300.





We see that as beta changes from 100 to 300, the emitter current increases from 0.989mA to 1.48mA. This is an improvement over the previous base-bias circuit which had an increase from 1.02mA to 3.07mA. Collector feedback bias is twice as stable as base-bias with respect to beta variation.
Bertus
 

bertus

Joined Apr 5, 2008
21,439
Hello,

Yes remove R8 and R10, I would also remove R6 and R7.
As for the calculations, I will do one of the stages.
Your powersupply is 5 Volts, you want about 1/2 of that so about 2.5 Volts.
Using a 2k2 resistor and having 1 mA going through it, the collector voltage will be 5 - (2k2 X 1 mA) = 2.8 Volts.
Assuming the beta of 100 ,the base resistor will be 100 X ( (5 -0.7) / 1mA -2k2) = 210k

Bertus
 
Last edited:

MrChips

Joined Oct 2, 2009
23,845
Remove C3, C4, and C5, each 2200μF. You don't need these.

Are you getting line frequency hum in the audio output?
 

Alec_t

Joined Sep 17, 2013
12,148
Remove C3, C4, and C5, each 2200μF. You don't need these.
It would, however, be advisable to decouple any power rail noise by, say, replacing R1 with a couple of 4k7 resistors in series and connecting their common node to ground via a 100uF cap.
 

MrChips

Joined Oct 2, 2009
23,845
It would, however, be advisable to decouple any power rail noise by, say, replacing R1 with a couple of 4k7 resistors in series and connecting their common node to ground via a 100uF cap.
Yes, I was getting to that. I was going to wait to hear from the TS if there is any problem with hum.
 

Thread Starter

Vipul Kumar 1

Joined Oct 20, 2018
79
Yes Sir Hum or rf interference problem solved now can i get the final schematic for 2 stage transistor amplifier reference with my schematic so that i can build it which can give good output because i understood the flaws in my schematic but different kind of solutions are there i am getting little confused
 
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