As I said I would get back with updates. I insulated both pcbs (bias- high impedance) using tape around them and I cover all the inside of the mic body with copper tape. Good signal and healthy signal? initially with phantom. No noise.??All my testing setup is good with any other mic.?
But.... after a couple of minutes (on a shockmount) a "squeeking" pitch raising sound starts and then the sound starts coming and going.
Can't blame the OPA IC? since with the simple electret it works really well - same pcb . And the capsule seems like it's working, since initially is functioning absolutelly properly.
Maybe a problem with any of the larger electrolytic caps on the high impedance pcb or the 2 small 20nf around the xlr pin 2-3?(for noise reduction)? or maybe the 1gohm resistor (which could be sensitive since its value is huge)?
I can't blame the bias pcb since it's providing constant 65V.
