Not to toot my own horn, but schematics of many mics I've tinkered with are on audioimprov.com. Not well organized, but there is a list of topics.
?
3-pattern electret made with 2 cardioid electret capsules (works great with TSB2555s):
?
3-patterns with double side "true condenser" capsule (2 cardioids back to back):
?
Variable pattern mic with one diaphragm grounded, backplate at 70V DC and signal taken there, other diaphragm variable 0-140V DC, grounded for audio:
?
and the ever popular basic mic circuits:
I need to add the OPA Alice to the basic circuits.
?
