Condenser mic jFET pre-amp design

[Bonsai]

If you are judging noise performance from Vonoise, you may be omitting any gain variations between the circuits. You need to account for gain.

The BF862 was 0.9nV/rt Hz IIRC.

 

[MarcelvdG]

At power-on, the gate is forward biased until the capsule is charged, so you don't get a long start-up time.

This is nonsense, actually. I overlooked the facts that they use a P-channel JFET and that they use different polarities for the capsule biasing, presumably depending on the chosen directional characteristic.

 

[Pip62]

I missed that they're using a P-chan too !

 

[HAYK]

The 3 layer capsul is for adjustable directivity.