Beat me to it I'd already started something similar, but for the 87ish style bodies that are being used for the U1621. Neumann actually made a microphone that was a fet47 circuit in a u87 style body, but I can't find the model number anywhere to bring up a picture.
What kind of price are you going to set for these PCB's? Are they being done in collaboration with poctop's DIY fet47 project? What are the final PCB dimensions? BTW, if you intend to use the fet47-style mic for bass amps and kick drums, the lower polarization voltage/sensitivity is actually a good thing.-James-
just need to remind that the PCB High impedance section isolation strategy is a critical aspect of my design
I put this project on hold due some unexpected issues, probably addressed to FET, untill I assemble one mic and test it for some days in the studio.In case of whatever: which FET can be direct replacement to Neumann 8280800022.4?