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Mic circuit(Can't make it work).

Chris_p80

New Member
Can i make a circuit (like a megaphone)
I tried two designs but didn't work
The components I used were
The mic ,a 0.5 watt speaker ,a BC 547(bc547C V1 E) transistor, a 10k and 100k resistor, a 104 ceramic capacitor and a 3.7v battery.
 

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That is a strange configuration for a mic preamp. Please post a link to the original circuit.

An electret microphone cartridge requires a DC bias current through it. Because your circuit has one end of the mic connected directly to a capacitor and nothing else, there cannot be a DC path through the mic.

No matter how many transistor connections you try, the circuit will not work.

ak
 
Last edited:
Is the link
(I was trying to make a circuit with a mic and a speaker ,a megaphone but this was the only one I found that didn't require a circuit board but it didn't work)

If there's just a silly picture, and no actual circuit (as in this case), it's a pretty good indication that the author doesn't have the slightest clue what he's doing, and it's never going to work.

You can't feed a speaker from a single small transistor fed from a microphone.

If you want a proper working electret mike preamp, refer to the opamp version on these forums here:


You would then need a power amplifier to feed a speaker.

As an electret mike is omnidirectional, it's probably a poor choice for a megaphone anyway.
 
Chris:

Please give us more detail about what you want to achieve. If you want to build a megaphone from scratch, how loud does it need to be? Are you trying to be heard over 10 people at a pool party, or 200 people at a ball game?

Do you want to build the amplifier, or is buying an amplifier module off egay an option?

ak
 

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