Comparison of JFETs for mic applications

[thor.zmt]

Is that Vgs of M1 in your circuit?

The Threshold voltage of 1.7V is a datasheet value. My BSS84 Model seems to indicate 2V Vgsth.

What voltage do you sim at the Drains of M2 & 3?

Especially for the Guru, a sim with all DC voltages and currents probed and spelled out:



Incidentally, I made up an A-Weight + 5th order 20khz lowpass network (all passive, VCVS & Ohm level resistance's) which suggests an 89dB(A) SNR @ 94dB SPL (or 5dB(A) SPL Self Noise), which is pretty Horrorshow in my books, except capsule noise scotches this big time.

HD @ 94dB SPL & 1kHz at 0.006% (or -83dB of pure H2) is also pretty pukka, innit?

Again, the goal was/is to reuse all of the BM-800 China Mike (except the saddle & Capsule where we go 26mm or 34mm Electret or 32/34mm LDC) including the PCB, mostly use commodity SMD Parts that fit the PCB.

And to make a studio recording Mic that betters relatively affordable (sub 500 USD) China made "recording microphones".

Not to make some supa dupa world record setting something. I leave that to Guru's.

I'm too pragmatic to be a guru.

I will show in a separate the thread the LDC Capsule version, with Bias from P48. It looks....



Thor

 

[Matador]

I for one appreciate the back and forth, even accounting for the snark.

Especially for the Guru, a sim with all DC voltages and currents probed and spelled out:

Why are the independent voltage source(s) added? Is it to monitor branch currents?

I'm curious what would change if you abandoned P48 power, and were free to set the MOSFET currents to whatever "optimum" you felt was best?