I used a small film cap. If you use an electrolytic, the + side goes to pin 2 of the XLR. For this capsule, which draws <500uA, a 100K resistor is appropriate. I didn’t use shielded wire, just twisted the pair to the capsule. Around my shop there’s not a lot of RF, and my preamp’s common mode rejection is good, so hum isn’t a problem.

The capsule is “hot” at 48VDC, so if it brushes against another mic or DUT, it needs to be insulated. Some clear nail polish takes care of that, and also attaches the capsule to the shrink tubing. The tubing isn’t shrunk around the capsule because the capsule has to be kept from heat.


Keeping the capsule cool while soldering leads to it is very important. I have a pair of pliers with a 6mm hole around the wire cutters, and it made a good heat sink as well as holding the tiny capsule steady. If the capsule gets hot enough to soften the plastic diaphragm, its frequency response will be affected badly.


Not much more to say, so here are pictures.

Heat sink

Chop stick, capsule, and heat shrink tubing

1uF cap and 100K resistor

Shrinking the tubing

while keeping capsule cool

Fingernail polish for insulation and securing capsule

Finished mic measures within 1.5dB of my EMM-6 20HZ-20KHz