I have a JLI2555 microphone capsule connected to a JFET Transistor that is then connected to a sound card that goes into the usb port of my laptop. The idea is that I want to record my voice using the microphone. The capsule and the JFET are powered by the sound card through a TRS Plug.
The circuit looks as the above image
The only difference is that the output is at V+ and there is no capacitor.
The TRS plug is connected to the JFET part of the circuit in the following way
The voltage of the sound card mic input has a voltage of about 2.85 volts. It is constant when I measure it with my multimeter, but when I connect it to the JFET and capsule it randomly drops to like 0.14 volts. It rises again later and drops again. When I speak into the mic the result is that I hear a buzzing noise and barely hear my own voice if at all.
Why does the voltage drops like this? Is it that the mic port does not have enough power to power a mic capsule like this?