Does the “simple P48” Circuit work with “true condenser” capsules?

A broken one-dollar flashlight

A Neutrik male XLR plug

A 100K resistor

A 2uF capacitor

A 2SK596 JFET from a BM-800 mic

A capsule from an MXL 990 mic

Just going for proof-of-concept here. Stuff is tacked together, insulated with shrink tube and tape.

And yes, it does work. It’s a crappy mic to be honest, but it works. So the idea isn’t crazy, BUT . . .

What’s wrong with it? It’s noisy. About the same amount of noise as an unmodified BM-800. The FET is of dubious quality, was pulled from a $15 mic and sat in a plastic bag for a couple of years. The capsule is small, and not biased heavily. The capsule is not properly vented to the rear, causing a huge bass rise and lots of handling and plosive noise.

                        . . . . . . and then  . . . . . .

Couple of days later. I happened to plug it into my TASCAM US-144mkII interface, and the noise is MUCH less than it was with the Focusrite Scarlett 2i2 gen3 interface. Hmmm... this bears looking into. Something’s going on I don’t understand, because the specs for the two interfaces don’t differ that much. But maybe this mic can be useful after all.

So I drilled a bunch more holes in the flashlight to vent the back of the capsule and stuffed it with damping material. It’s not bad with a quiet interface. Is it worth building something similar, maybe in a BM-800 body with a 34mm capsule, a known good FET, and so on? Personally, I wouldn’t. It’s not much harder to put together a mic with a Schoeps circuit which will make the most of the capsule. But this has to be the simplest circuit for a “true” condenser mic.