How do I make a volume control for a electret mike

Caleb Chia · 9th September 2008, 03:11 PM

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]

[/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 · 9th September 2008, 05:00 PM

this works better..

Caleb Chia · 10th September 2008, 12:10 PM

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

sivan_and · 10th September 2008, 01:51 PM

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 · 10th September 2008, 01:58 PM

Quote:

Originally posted by Caleb Chia
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 · 10th September 2008, 01:59 PM

Quote:

Originally posted by Caleb Chia
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 · 10th September 2008, 02:03 PM

Hi sreten

You where faster than me ...

Mooly · 10th September 2008, 02:14 PM

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 · 12th September 2008, 09:35 AM

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 · 12th September 2008, 11:50 PM

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!

9th September 2008, 03:11 PM	#1
Caleb Chia diyAudio Member Join Date: May 2008	How do I make a volume control for a electret mike 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][/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

10th September 2008, 01:51 PM	#4
sivan_and diyAudio Member Join Date: Dec 2004 Location: Dxb / India	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.. __________________ SivanandBalan

10th September 2008, 02:03 PM	#7
Tube_Dude diyAudio Member Join Date: Mar 2002 Location: Aveiro-Portugal	Hi sreten You where faster than me ... __________________ Jorge

10th September 2008, 02:14 PM	#8
Mooly diyAudio Member Join Date: Sep 2007	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.

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10th September 2008, 12:10 PM	#3
Caleb Chia diyAudio Member Join Date: May 2008	what if the first stage is clipping? Is there a way to reduce the gain?

12th September 2008, 09:35 AM	#9
Caleb Chia diyAudio Member Join Date: May 2008	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!

12th September 2008, 11:50 PM	#10
Caleb Chia diyAudio Member Join Date: May 2008	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!

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