That's playing the role of the capacitance of the capsule itself.What is "K1" near the capsule?
You'll probably want that to (at least temporarily) be a trimpot indeed. 4.7k just happened to be the optimal value that was appropriate for the simulation (i believe..?).What is the "R*" 4.7k resistor? On the OG schematic, there's a 25k trimpot on the source leg of the 2N3819 JFET. Is the "R*" just a standard 4.7k resistor?
Once again, a simulation thing. Any 36V zener will do, indeed.The D1 Zener Diode is noted specifically as a CDZV36B. Will any decent 36V Zener Diode do the job in its place, or is there something else I should be aware of?
Probably standing for "Phantom Resistor 1/2" - those are (by standard) inside your preamp. They're in the simulation schematic in order to have the same conditions for the powering as you'd get in real life (to get the appropriate voltage readings etc).What are "PR1" and "PR2" on this schematic?
Yes, XLR2/3 are at the node between PR1/2 and the respective 2.2k resistors.And lastly, are pins 2 and 3 from the XLR connector joined here?
You proooooobably don't need 250V rated caps for the 33nF's - those will end up being on the huge side. Just plain old 63V types are plenty fine, and they're tiny by comparison.I have begun putting together a list of components on RS, but I'm in doubt of which cap types to use
As pointed out a few posts ago, you can replace that single 10nF with a(nother) 33nF, but once again, no need to go for ridiculously high voltage ratings, this is not a tube mic
For the 120pF cap, you'll want to make sure the material is C0G / NP0. Can't see an exact part number in your parts list, but i recently stocked up on some of those tiny blue TDK ceramic caps. Colour is no guarantee of construction though, so you'll want to check that in the datasheet.
You might consider splitting up the R9 into... I don't know, 6.8k + 3.3k, or 7.5k + 2.2k, something in that ballpark - see the original U87 schematic. There, R9 is actually a 6.8k + 560 resistor, and one can apply signal from a generator (a line / headphone output, in your case) there, and be able to monitor the output of the mic connected to a preamp input (on your interface, which would also provide the phantom power).Or should I just go ahead and build the ORS 87 Modern PCB and do the biasing straight on the board itself with a trimpot of some variety in place of R*?
Trying to get a signal connected "in place of" the capsule gets complicated and delicate, if you also want to have the effect of the tone-shaping feedback network.