value of R4 & which mic to be used

[rajaram04]

Hello sir i ve a circuit diagram & link here



http://www.circuitdiagram.org/microphone_amplifier.html

here whats the value of R4 & which mic is here in the diagram & description i am not getting it

 

[arbabar]

R4 can be any variable resistor to stabilize the dc current. Take it 10k or 5k variable resistor. by changing the resistance u can adjust its output.
600ohms Resistance is the mic (resistance)

 

[rajaram04]

no no i mean which mic ? as u said 600 ohms resistance means it may be any electret mic also or any other one ? please mention the type . . thanks

 

[arbabar]

sorry its impedance!!! not resistance.
u can buy it from any of the electronics shop. named as 1.5v and 600ohm impedance mic(Piezoelectric microphone)

 

[rajaram04]

hmm ok but i dont think that this type of mics are available in our area or one may easily understand what i am asking there so would you please give me any other substitute of it ? please comment
thanks

 

[sky_123]

The most common mic you'll encounter is the humble electret mic element, used everywhere. It may work with an electret, but
of course you need to provide some power to the electret (as you know), much like the design in the earlier thread. So, you could try a similar scheme to power the electret, i.e. a resistor and a capacitor.

This design is a bit crude, but something like 100k or 470k should be fine for that resistor R4. By the way, the web page has
a mistake, it says use BC337 (an ancient transistor which is NPN, not PNP). They probably meant BC327.

Of course, if you're using an electret then you may as well use the earlier circuit, it is better. Unless you really need to run off 1.5V
like this circuit.