ORS87-Plus - Open-source U87 mic project (optionally FET847)

That's a good catch on the designators, apologies for the confusion.

Regarding some of your other questions, have you read through all the text i took the time to write here?

- RH and CH optional additional high-frequency reduction - 10k & 1nF can provide an additional 2dB of attenuation at 10kHz, if needed / desired
- C7 selection - DC-blocking output capacitor between the JFET drain and output transformer; several footprint options available (2.5mm-pitch electrolytic, 5mm or 7.5mm-pitch box film, and up to 15mm-pitch axial or epoxy-dipped radial film)

Regarding C7 type, "RTFM" again:
"If you're fine with a normal box-film PET capacitor for C7, change the row 4 quantity from 1 to 2
If you're fine with an electrolytic capacitor for C7, change the row 2 quantity from 2 to 3
If you wish to use a polypropylene film capacitor for C7, also add the "ORS87-Plus PP capacitor" to your basket
If you wish to use the additional high-frequency attenuation option (RH and CH), change the row 5 quantity from 3 to 4, and the row 11 quantity from 6 to 7"

Regarding headers - if you buy the normal 0.1" pin-header strip kinds, they don't have a "pin 1" (to the best of my knowledge). Even more so, if you buy a longer strip (better deal) and break off pieces as long as you need / want.

The high-pass filter is OFF when the two inner-most pins (with traces) are connected, and ON when they're not (outermost pin is floating / not connected to anything).
The pad is OFF when the two outer-most pins are NOT connected, and ON when they are (innermost pin is floating / not connected).

Nothing that could not have been determined with a board in hand, i think? And why would you necessarily assume "the pins closest to the edges are ground"? If it's not clearly visible, an ohmmeter can help clear that up in literally seconds...

Regarding the transformer, the ends of the single secondary winding get connected to S1+ and S2-.

I should really try to make time and get that build guide written up...

Thank you for the reply. i did read through your comments before asking any questions. I understand what RH and CH do based on your comments, my question was concerning the designation on the PCB. I assume RH and CH are labeled R9* and C5* on teh PCB, but wanted to make sure I was correct.
The header question is about pin designation. The schematic shows pins 1,2, & 3 but the PCB does not, so it was not clear to me what jumper placement was required to achieve the desired result.
There is no mention of C7's value anywhere in your written instructions nor is it labeled in the schematic. I understand it can be made up of any type of preferred material, but the value should be the same. By ordering the "ORS-87-Plus PP Capacitor", it is clear the value is 1uf 63v. Using your written instruction to increase the quantity of either row 2 or row 4 would yield additional capacitors of .1uf and 3.3pf. I've included a screenshot of the first 5 rows of components in the Mouser basket.
If you are interested, I can create a build guide after a successful build and share it with you for editing/approval. I'm not looking for any credit, just looking to help out where I can.

I stand by my statement that pin headers don't have a "pin 1" designation. And add to that the fact that, if one chooses to mount vertical switches in those footprints, the direction the lever points is opposite to where jumper pins would need to be connected, so... Yeah, i hoped for some "figuring out" skills on the part of the builders of this project, but oh well...

Ah poop, did they jumble up the displayed order of components in that BOM list? Dang it...

I just want to start by saying everything you have stated is 100% accurate. My questions were simply for clarification. Of course, there is no PIn 1 designation for a header. I understand that. My point is, if there were some designation on the PCB showing which hole correlates to which pin in the Schematic, that would be helpful. When installing a switch this would be even more useful for orientation. Hence the reason for my question about jumpers and their position.
I still have some of the same clarifying questions.
Does RH = R9*?
Does CH = C5*
Is C7 a 1uF capacitor?

Yes, yes and yes. And i updated the capacitor selection instructions in the Mouser BOM section.

EXCELLENT! Thank you very much!

As I mentioned. I was willing to create a build guide. I did do that. It is maybe a bit overkill (20 pages w/ pictures) for the experienced builder, but it includes a step-by-step of the build from bare PCB to completed microphone. If you are interested, I can share it, but not sure how to get it to you. Of course, I would welcome any edits/suggestions.

You could at least try it out - they don't seem to be too-too-too far apart specs-wise, and look to be from the same "family".

I'd kinda rather not. There's barely a few components in the whole thing, and i've done my best to minimize the amount of different values, to begin with. And i really hate to sound like i'm "gatekeeping", but if people are much too lazy(?) to cross-reference even just two or three numbers (between the schematic and the board), well... Maybe they should also stay away from hot soldering irons?

OK, thanks for your feedback. We got it.