Maybe your electret mic is a 3-wires one instead of a 2-wires one.dear audio guru,
I have made this circuit as per schematics with TL071 and ur modifications, completed last night. Circuit seems working ok as pre amp but it is not sensitive as i have to eat mic to get sound from my amplifier.
Maybe your electret mic is a 3-wires one instead of a 2-wires one.
Maybe your electret mic is connected upside-down. Its metal case and the pin connected to it is supposed to connect to 0V.
I don't know which circuit you made. My mic preamp circuit that I attach here again has a voltage gain of 101 which is fairly sensitive. My instructions say to inrease the value of R3 for more gain.
Here is what another member said about my mic preamp circuit:
"I tried the setup with out your mods - thanks guru - and the results were astonishing to say the least.
I stood back about 20 feet and spoke with a normal voice. The sound recorder picked it up as if i was standing right next to it..
With your modifications the circuit is more then I had expected! Unbelievable.
By the way, if it isnt too much to ask, what is the gain set at with the 100K resistor?"
The red and white microphone wires should not be connected to the same place.
Leave the red wire where it is, and connect the white wire together with the shield (screen) to ground (common, 0V).
The resistor which gives power to the microphone is wrong. It it 150k (brown, green, yellow, gold), but it should be 10k (brown, black, orange, gold). 4.7k (yellow, violet, red, gold) would also work.
That is a 3-wires electret mic. My circuit is designed for a 2-wires electret mic and needs modifications to work with your 3-wires mic.As for mic i used only two wires (white wire NOT grounded with shield) beacuse of this image attached; fig1. (1:signal, 2:5v, 3:Ground)
Of course the 3-wires mic will not work when you short its pins together. Pin1 is +5V, pin2 is the output that probably needs a coupling capacitor to feed the preamp and pin3 is the metal case and is ground for the shield of the cable and is 0V.When i connected preamp output to mic jack pin1 and pin2 both tied together it was producing lot of noise, how ever i connected preamp output as shield to pin 3, and signal (redwire) to pin 2 and that bomardment noise vanished (i dont know why
Your attachment did not work. We don't know which way the pins on your mic should be connected. Try it both ways.i am attaching image fig1 which i got from a website, according to them pin 2 is 5v; pin1 is signal)
It is connected wrongly for a 3-wires mic.simple mic is working ok in this config fig2.
any way i hook it with only two wires shield and ring at mic jack and got low noice (only humming and speaker feedback is there)
An electret mic works very well when its pins are connected properly.The circuit is picking up the voices very good like fan, scratching over mic wire or table it is very sensitive when the wire or circuit board is moved but my voice i am speaking at 3 foots is not upto the satisfaction. It is relatively better when I speek under one foot distance with normal voice.
There should not be any hum. Hum is caused when the pins on the mic and the shielded cable are not connected properly.Actually i am using a voice recongnition software to send computer commands but due to this issue and may be little humming/noise, software feel diffculty in recongnizing my commands some times it is not listening at all.
Why use an ordinary TL082 dual opamp? it has the same max voltage gain as any other opamp but it has no input bias current since its inputs are Fets. The lack of input bias current does not make it very sensitive as a mic preamp.Enjoy this clip-on mic, and if you want sensitivity any set of TL082's will get you to be able to 'Hear Crickets Chew Grass'.
That is a 3-wires electret mic. My circuit is designed for a 2-wires electret mic and needs modifications to work with your 3-wires mic.
Of course the 3-wires mic will not work when you short its pins together. Pin1 is +5V, pin2 is the output that probably needs a coupling capacitor to feed the preamp and pin3 is the metal case and is ground for the shield of the cable and is 0V.
Your attachment did not work. We don't know which way the pins on your mic should be connected. Try it both ways.
It is connected wrongly for a 3-wires mic.
An electret mic works very well when its pins are connected properly.
There should not be any hum. Hum is caused when the pins on the mic and the shielded cable are not connected properly.
Here is a 2-wires electret mic and a 3-wires electret mic with the ways they connect to a preamp circuit:
Picking up of scratching over table,mic,wires doesn't measure the sensitivity of mic. All will pick those. If you're using 100% volume with 'mic boost' on computer, then it is not even sensitive anywhere near standard level.
I didn't expect that question...so... ? what to do now ?
You forgot to say which microphone and which opamp you have.Hello audioguru,
Can I use 5V (or 12V) instead of 9V as PWR IN.
It won't make any difference.would there by any benefit in terms of noise if this circuit is converted to dual supply with two 9V batteries?
I never used one because I don't use extremely high gain for a mic preamp.I am also considering using the OPA134 which was suggested to me by audioguru.
The circuit does not need a pot to adjust the bias on an electret mic.Will the use of potentiometers on the electret bias and opamp gain resistor influence the noise level?
You will find that background sounds will be much noisier than electronic noise from the circuit. You might hear some electronic noise if you turn off the mic.I am currently using metal film resistors and I suppose the potentiometers (multiturn high quality) will be more noisy?
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