FET Mic with dedicated power supply.

[Gus]

That looks like the schematic Flatpicker drew after we had a conversation it is a simplified KM84 like circuit.  That works fine with Phantom. 

Listen to what bockaudio posted the external power supply can matter.

The twisted pair cap was made of wire wrap wire I could not find a good small pf cap at my bench at the time.  I built that circuit in two different bodies.  I matched both jfets as close as possible so both circuits bias the same way and with a 3.9K source resistor.  Why a 3.9K because that what was in the PDF "microphones" and I wondered why 3.9K was shown in the PDF.  I noted an interesting thing with the IDSS and the ID the circuit runs at.  One was built in a piece of fence pipe and the other in  a  MXR V67 body.  The sound seems to follow the body my simple test was to exchange the capsules between the bodies.

One of my best builds is a external powered solid state microphone.  I have a number more in sims some hybrid some all solid state.  Some transformer and some transformerless
IMO you need to think about what makes a tube plate out to output transformer sound the way it does?
What makes a solid state transformer out sound like it does?
What makes a tube transformer out sound like it does?
What are the interactions?
How deep do you want to research this?
I stopped building testing sometime ago because the next steps would require expensive instrumentation and a good test chamber and a lot of time to do correctly.  I even looked into vacuum chambers for coating diaphragms and winding machines for building my own transformers.  IMO not worth it unless I had a microphone company and you need to think about liability.

With 48VDC phantom the current is limited by the 6.8k resistors this limits the current and power.

QUESTION has a phantom powered microphone ever started a fire?

If you use an external power without voltage and current limiting you need to think about available current/power at the microphone end and in the power supply if it fails you don't want a fire or shock hazard. 

 

[Pip]

Yes it is again not my schematic. I know who gave it to me but I dont know where they got it from and I actually have a mic built already using it. Thats why I picked it as a talking point.


I am not leaving this as a dead issue. I just have been really busy. Life in the way of life again. I am also deep into the last stages of rebuilding a console and it is sucking up all my spare time. Don't leave this alone though I don't have to be the only one driving the bus. I put to the community come forth with a viable LDC mic schematic with either a transformer or Schoeps type output, that has obvious directionality in concept to both phantom and multi-output powering schemes and I will build it both ways and test it! I will continue to refine my approach as well and maybe this will take wings.