Facebook
Google
GitHub
Linkedin
DrewStupid
- Joined Nov 28, 2018
- 64
Robin.. would that be a ceramic cap ?Heres an easy electret microphone circuit
How can I do electret microphone noise filter?
- Thread starter ramazanalkan
- Start date
So I should use 5V power or I can use 9v and change 1k r1 to 6k8?
Sory I can't understand
They are almost the same just made from different manufactures, please recheck my post #12.
That is depends on the PCB size and your PCB layout.
The NJM5532 preamp circuit is completely wrong:
1) The minimum supply for an NJM5532 or NE5532 is 6V so it barely works with only 5V. Use 9V with a bypass capacitor.
2) An electret mic draws 0.5mA and needs a few volts across it so with a 9V supply and a series a 1k to 47uF filter producing about 8.5V then the resistor feeding the mic should be 10k. When a lower value is used then it reduces the output level. The filtered 8.5V should also feed the bias resistors for the opamp.
3) The Jfet in the mic and the 10k resistor powering it results in a source impedance of about 2.7K which is in series with the 47k input resistor of the preamp circuit then the gain is only 1M/49.7k= 20.1 times which is much too low. The opamp should be non-inverting with a fairly high input resistance then the gain resistors can be less with a gain of 200 times.
4) The two 470nF input capacitors pass earthquake frequencies down to 3.4Hz.
I think the low frequency noise is mains hum that is picked up by all the messy wires on the breadboard. A compact pcb or stripboard should be used (maybe in a grounded metal box) to feed a shielded audio cable connected to the line input of the computer.
Here is a preamp made for an electret mic that produces very low noise. An NE5532 can also be used instead of the TL071.
1) The minimum supply for an NJM5532 or NE5532 is 6V so it barely works with only 5V. Use 9V with a bypass capacitor.
2) An electret mic draws 0.5mA and needs a few volts across it so with a 9V supply and a series a 1k to 47uF filter producing about 8.5V then the resistor feeding the mic should be 10k. When a lower value is used then it reduces the output level. The filtered 8.5V should also feed the bias resistors for the opamp.
3) The Jfet in the mic and the 10k resistor powering it results in a source impedance of about 2.7K which is in series with the 47k input resistor of the preamp circuit then the gain is only 1M/49.7k= 20.1 times which is much too low. The opamp should be non-inverting with a fairly high input resistance then the gain resistors can be less with a gain of 200 times.
4) The two 470nF input capacitors pass earthquake frequencies down to 3.4Hz.
I think the low frequency noise is mains hum that is picked up by all the messy wires on the breadboard. A compact pcb or stripboard should be used (maybe in a grounded metal box) to feed a shielded audio cable connected to the line input of the computer.
Here is a preamp made for an electret mic that produces very low noise. An NE5532 can also be used instead of the TL071.
