I made contact mic with JFET preamp circuit(very basic). It works fine. Then I tried to use my stereo microphone with same setting, so I plugged my stereo microphone(cheap one) to input of preamp but I can't listen any sound. Nothing noisy or no cranking sounds..neither.
What I've noticed I used my socket with mono socket (GND/+) as input, but the mic uses 3.5mm stereo jack with 3 poles. As I knew it has (GND, -, + in order) so I expected I could just plug? Or can I just select GND/+ and solder on mono plug?