Friday, 30 October 2015

Build a Studio Condenser Microphone (DIY) Part-1

I posted about a simple circuit in the previous post. But after some experiments of different capsules i have found some difference in their working. And so, there must be changes in the circuit. I got a 16mm small diaphragm capsule and i wanted to test it. But the 10k resistor was creating a little noise. So i designed this circuit:
 Here you can see the one phase was needed for the unbalanced output. I don't know why but a 30M Ohm resistor was the only suitable resistor to power the capsule. And none other were working and i'm just trying to figure it out why. 

So the phase is taken from FET and then fed to the preamp circuit. Nothing very special here. This is just like the previous one. 
By decreasing the value of 30M Ohm resistor you can make the other non electret microphone capsule work with it.

If you have an unexpected noise then you may need to place a diode between gate and the source (ground) of FET.

So how we can have a balanced phantom powered microphone ?
As i told you about the phase that is taken from source of FET. We need to have another phase from drain too. So that we'll be having two outputs. Here is the diagram :
The both output is fed to the base of both PNP transistor. I was about to use BC557 but i found that they are little noisy. You may not measure that tiny noise but that is disturbing. So i replaced these with A1015 which are specially made for a low noise amplifier and i have found a good use of them here ;)
Pin 2 and Pin 3 are filtered by their caps 0.022uf which is a 22nf to avoid noise.
A 9v Zener diode is used as a shunt regulator to supply 9v to FET and transistors because for this circuit 9v is sufficient. Variation in voltage can also create noise.
For the phantom power filtration we have a RC flter circuit in it. If you observe we have 10uf after 9v Zener Diode and then 100 Ohm resistor and then again 100uf cap. And you may want to try different values of these caps but i have already played with them and found that these are the pretty standard & suitable values.

Have a wonderful project. Hang on in the part-2 i'm gonna post the practical work.