Here's the completed PCB for the MXL 990B microphone. Easy to build, and as I mentioned in Part One of this project, the instructions are very well written and clear.
I did this outside. It's not on the surface of the moon. It's the green tarp I paint over. That black/grey color is paint, not moon rock!
On the right in the picture is the switch to choose the cardioid (front diaphragm of the capsule) or omnidirectional (both diaphragms) pickup patterns.
Since the inputs from the capsule are high impedance, the connections are made up off the board, so that they are air insulated. The red arrow points to the joint between one switch terminal, the JFET, and a resistor. The front diaphragm lead will be soldered here in the final assembly.
The other side of the switch is for the omni pattern, and the back diaphragm lead will go there.
The headbasket (screen at the top over the capsule) just comes off with 2 screws.
You can see the old PCB near the body of the mic. I'm saving it, but I'm not sure I'll ever use any parts from it.
We'll reuse the pedestal with a new mount that comes in the kit.
Unscrew that ring mount from the pedestal.
It also looks really cool.
Then slide the PCB on where the old one was, and solder the capsule leads to the PCB, as well as the output leads. Clean those connections with the flux remover - on a q-tip instead of spraying.
To protect and insulate the connections to the switch I highlighted above, I painted the switch joints with conformal coating. First time I've ever used it. It's like paint (smells a bit like nitro lacquer) and insulates that sensitive, high-impedance joint from becoming corroded.
Plug the mic into phantom power, connect one DMM lead to the chassis (ground), and one to a specific diode on the board (cathode end of D5 if you're building one...). I did this on my recorder since I don't have phantom power in The Dungeon!
There is a diode in the circuit that can be replaced with a different value to increase headroom and make the mic more able to handle high SPLs. I won't be putting this in front of any really loud sources, so I'm sticking with the stock configuration maxed out for best sensitivity and lowest noise.
On the left is my finished mic. The old headbasket is on the right. It's painted the same sickly champagne green the body was. You may recall I resprayed the body a hammertone gray; I wanted a classic vintage German mic look and I think I captured it.
Now to go record something!