How do I make a volume control for a electret mike

[Caleb Chia]

Hi, sorry if this is in the wrong section,

I just finished this 3 stage FM transmitter kit (from jaycar), and it works awesome as a bug but its too sensitive for a mic and keeps clipping.(I want to stick it inside my guitar) Do you guys know a good way of putting a volume control on an electret mike?

here is the input circuit

[/IMG]

Do you think this would work? If so, what value of potentiometer would work best? Would the reduced impedance change the frequency response of the mic?

thanks

 

[sivan_and]

this works better..

 

[Caleb Chia]

what if the first stage is clipping? Is there a way to reduce the gain?

 

[sivan_and]

i don't think this stage will clip..unless the condensor mic is soo close to the sound source..reduce the gain..(increase 22K)..but that value is still high..

 

[sreten]

what if the first stage is clipping? Is there a way to reduce the gain?

Hi,

Put a resistor between -ve and the transistor emitter.
It is called degeneration and the local feedback will
linearise the stage as well as reduce gain.

🙂/sreten.

 

[Tube_Dude]

what if the first stage is clipping? Is there a way to reduce the gain?

Use a emitter resistor, for some emitter degeneration and consequent gain reduction...

 

[Tube_Dude]

Hi sreten

You where faster than me ... 😉

 

[Mooly]

You could,

Use a FET as a source follower, followed by a volume control. You need a buffer amp with a high input impedance with a condensor mic. You say at the start you want less gain not more.
Or use a suitable OpAmp if you have the appropriate supply, and don't forget that the output from a mic capsule can be very much higher than you might think on loud transients.

 

[Caleb Chia]

Thanks a lot for the replies.

Ill try the emitter resistor first, (more linearity sounds nice!) Ill just jam a small 50k multi turn trimpot between the transistor and the track..hope I dont fry the transistor while soldering it on, I left the legs too short!

 

[Caleb Chia]

I just soldered it in and it worked beautifully. No trace of clipping ,crystal clear and linear as a ruler!
Thanks a lot. You guys rock!