Main PCB draft. I also made some tiny adjustments:
1) The parts numbering continues from the main schematic to the oscillator PCB, since I'm confident I'm not adding more parts at this point.
2) I measured the screwhole placement in the Aurycle mics I have to verify that I had those in the correct place. These are the same body size.
3) I made an important change in the main schematic which we didn't discuss yet: I made the Zener regulator from a lower value zener and white LEDs. I had found
this thread a while back when I was looking for a solution to Zener noise. Since we only need to hit 12V or less on this regulator, this seemed like a good opportunity to use it (I can't very well do so if I need a 30V regulator, for instance). Zener diode noise is extremely well discussed in many, many, many places if anyone needs to look up more info. The 6k2 should be sufficient current limiting, but you might want to take a black marker or paint over the LEDs to blot them out so you can actually see the circuit ... them things are bright. If anyone has further suggestions about this, let me know before I call this one ready to prototype.
4) I'm still not 100% sure about the trimpot value in the oscillator in this mic (I've only done voltage oscillators this month for the first time, and it was all in u87 variants), but I bumped it up to 10K.
5) I put pads on the board for the capsule, but I really suggest just doing it deadbug stye.
6) I added a high pass filter that has worked well for me in the past. Yes it changes the bias slightly, but they're matched so you should be fine. I cannot measure or hear the noise increase on my equipment (but I assume it's there). It's 150Hz but if that's too much for you just increase the size of the resistor.
7) I added a pad. I opted not to do it like the original because it would have involved an extra wire run. If you're going to use it, you can route the capsule backplate connection through the switch on the way to the PCB. It's only connected to the PCB when you've got the pad in, so the PCB resistance (which I think is about 300M for FR4) loss shouldn't be a problem.
8) As suggested, I left out the input capacitor. If it's my mic, though, I'm probably ditching the trimpot, grounding the 1G, and selecting R10 for the bias. I couldn't fit both trims and it made for a MUCH better layout to just omit the cap completely.
9) Lastly, I've opted to omit the corrective EQ for the capsule. Here's my thinking: Anyone who is grabbing one of these PCBs probably isn't satisfied with the 25mm 67-style LDCs and the capsule should be the thing they replace before touching the circuitboard. There are many better options for capsules out there. If you want to get super cheap about it, you can even just omit the oscillator completely and this works as an Alice and the transsound large electrets don't usually need EQ correction either, and frankly I think they sound awesome compared to the stock capsules that come in the 990 etc. (Though I think that the larger 67-style one that comes with the Aurylce FET kits sounds better than both and I like that in my modded 990 over the other Kx7 capsules I tried.)
I'm about ready to upload these to OSH just for a visual check, but I need some time away from Eagle. Once I'm fully satisfied with it, I'll share the Eagle files. I'm also going to move as much of this information to a new thread for shared OSH Park circuits. I'll see about getting the generic FET+emitter follower PCBs done up as well, as well as a couple +- single-transistor voltage oscillators for multipattern versions of these mics. There are still some better PCB options overall for that (e.g. Chunger's oscillator PCB, if you can find it, uses a more stable chip arrangement) but I think this would be helpful to have access to.
Really don't understand why this won't display:
https://dl.dropboxusercontent.com/u/9878279/Jon%20Patton%27s%20layouts/MIsc/Schoeps%20style%20transformerless%20circuit%20-%20PCB.png