So this is yet another lost and found article -- describing a schematic for a mic preamp which I really like and which I more than likely found on the Internet some 5-10 years ago. I've used this circuit a number of times as it comes in quite handy: In a nutshell, it gives you a somewhat useable phantom powered microphone at a price of EUR 10 where the XLR connector is still half of the expense. If nothing else, it's worth a shot when you just need *something*.

The use of this minimalistic schematic as a "Plug-Mic", prototype and assembled final microphone
So this is essentially the other thing within the sound realm I build multiple times: This circuit takes an electret condenser capsule, uses two transistors and a handfull of discrete components to power that capsule and deliver a somewhat(!) balanced output signal. I just recently went on to see whether I can miniaturize the whole thing to the point of the complete amp fitting into the XLR jack -- and yep, there's only the capsule as such poking out, making it a quite rugged design that gives you probably the smalles physical footprint when it comes to "just have another throwaway-mic with an XLR connector ready".

Parts list:
2 Transistor BC558
1 Electrolytic Capacitor 10μF
1 Electrolytic Capacitor 0.1μF
2 Capacitor 0.1μF
2 Resistor 100kΩ
2 Resistor 5.1kΩ
1 Resistor 33kΩ
... and the electret capsule of course.


I may or may not have taken lots of inspiration from other sites on the internet for this, however, as this "thing" is by now 6-7 years old, I have no clue what the original sources may have been. If someone claims that I saw this circuit first on his site, that's perfectly reasonable. I do not claim any originality.