FEELER - Solid-state microphone upgrade boards (OpAmp, JFET, U87A, FET847, ORS87-Plus)

[MicMaven]

Um... er ... I recently purchased a couple of nice bodies and want to build a mic with a single-sided condenser capsule requiring external bias.

1 Which board is most appropriate? I believe the "FET847 engineeringly-sane version" with through-hole components would do the the job and suit my construction skill level - best to ask than guess wrong.

2 Is a BOM on file with a supplier, or a list of all components I can use as a reference whist shopping?

3 I presume Mouser or Digikey are good sources for buying individual parts (i.e., having few minimum-number-order requirements) - but are there any other good sources for buying single components?

4 I can purchase the board directly from the PCBWay?

Thank you. I figure such matters are know by veterans, but I am still a rookie with just enough knowledge to be dangerous! Happy trails. James

 

[Khron]

1 Which board is most appropriate? I believe the "FET847 engineeringly-sane version" with through-hole components would do the the job and suit my construction skill level - best to ask than guess wrong.

That sounds about right if assembling it yourself is a criterion.

2 Is a BOM on file with a supplier, or a list of all components I can use as a reference whist shopping?

Only got as far as scraping together BOMs on Digikey & Mouser for the ORS87-Plus project; I figured i'd get to the BOMs for the other through-hole projects AFTER i prototype at least one of each board (set) and finalize some component value choices. And also see about putting together some semblance of some build guide.

3 I presume Mouser or Digikey are good sources for buying individual parts (i.e., having few minimum-number-order requirements) - but are there any other good sources for buying single components?

Can't really help you with that, unfortunately. But especially if you're into DIY, why (or rather HOW) couldn't you have a stash of extra parts, for modding / tweaking / other projects? I only buy one-offs if they're really pricey, or very specific things (like a big switching power supply or something). But passives & discrete parts? Tens / hundreds of each, easy...

4 I can purchase the board directly from the PCBWay?

I'm afraid only the ORS87-Plus is (or will be) available on PCBway, the rest i will be selling directly, one way or another.

Shipping across the pond will be pricey though (then again, it is within Europe as well, because Finnish Posti prices)... If all goes well, there should be a US distributor as well, once things are "polished up" all the way, but information will be updated once that's settled

 

[hkung]

Yes Khron, this is definitely a very interesting thread! Thanks for linking
How would one go about acquiring a pair of the Opa Alice for cardiod? I'd be interested in having them populated as well if you'd like to make them for me, as long as you think they could fit the Baba express 251 house in the other thread where you linked here from.

35mm width on top (closest to capsule) screws, 33mm bottom, and 80mm height/"axially" if I measured correctly. As per previous, I'm a beginner and this would be my first LDC. The plan is to use Ariannes K47 capsule with the OPA Alice circuit in the 251 house (I know, blasphemy but it looks cool!). Bambi would appreciate any handholding on these first steps on how to populate the PCB properly. With that said, I have access to some pro troubleshooting help if (when) I fk up.

In either case, quoting a wise man I'm mostly interested in getting it working with minimal fuzzing about.

 

[Khron]

How would one go about acquiring a pair of the Opa Alice for cardiod?

Well, you'll have to hold on for a bit longer - i've yet to populate even a single one of those boards, not to mention test out everything etc. It's been pretty hectic here these past few weeks, and we're about to (hopefully) put down an offer for a house next week, so...

as long as you think they could fit the Baba express 251 house in the other thread where you linked here from.

35mm width on top (closest to capsule) screws, 33mm bottom, and 80mm height/"axially" if I measured correctly.

Is that between the centers of the holes?

Bambi would appreciate any handholding on these first steps on how to populate the PCB properly.

https://groupdiy.com/threads/feeler...fet-u87a-fet847-ors87-plus.87606/post-1151752

 

[Khron]

In other news, i DID manage to squeeze populating one of the MicroSchoeps boards, split into 2-3 afternoons, and, well... I'm pretty chuffed




To my surprise, even the cable chuck fits over the whole thing Only in one of the two possible positions, but still...



No, i didn't have all the capacitor values i wanted in stock, so i improvised... Hey, it's a prototype, whaddya want?

 

[hkung]

Well, you'll have to hold on for a bit longer - i've yet to populate even a single one of those boards, not to mention test out everything etc. It's been pretty hectic here these past few weeks, and we're about to (hopefully) put down an offer for a house next week, so...



Is that between the centers of the holes?


https://groupdiy.com/threads/feeler...fet-u87a-fet847-ors87-plus.87606/post-1151752

Of course, no rush from my end. That's wonderful! Congratulations (hopefully)
Consider me on the waiting list please, following this thread for updates

Yes, between the centers

EDIT: Ok that MicroSchoeps is seriously awesome, gonna want a pair of those as well please

Cheers

 

[neowalla]

Might there be any interest in (what i hope to be) a teeny-tiny SMD board for "Linkwitz-modded" 1/4" omni electret capsules, with a Schoeps-like output stage, that should possibly-hopefully fit inside an XLR connector shell (~20 x 11mm)?

I've had this kicking around for some time, just to actually use up the last five Panasonic WM61A's in my stash (they're not doing me any good gathering dust). Call it a poor man's OM1 (as from Line Audio)? I also grabbed a few of these capsules from TME some time ago, just for shits & giggles, to see just how lousy (or not) they might be...

I'm interested in any and all of your projects in this thread and will likely build all of them. It's an addiction you see?
Anyway, as an alternative housing you could consider these XLR to 3.5mm adapter things.
https://www.amazon.ca/gp/product/B07L42PBY5/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

There is a build thread on that other mic building group about using these with a simple P48 circuit and small electret capsules.
https://groups.io/g/MicBuilders/topic/103491193#msg36007

 

[pmfalcman]

(...)
I have toyed with the idea of an Opamp-Alice for SDC's, but there's no real standard in length or width for SDC bodies / boards, so...

As more people could be interested in PCBs for SDCs my first, off the top of my head idea would be to make a one-size-fits-all board ("too small" width- and lenghtwise) and employ your idea of mounting on stiff wires but from the XLR side. Regular electrical wires of 2,5 mm sq should be perfect for this - stiff enough and easy to obtain.

 

[Khron]

and employ your idea of mounting on stiff wires but from the XLR side

What about the capsule side?

 

[jp8]

Nose cone has to be kept in place as well, somehow. Typically done by attaching it to the PCB. You don't want it to twist or be pushed into the SDC tube, causing poor contact with the capsule.

In the end, there are not that many low-cost and easy to obtain SDC bodies suitable for diy projects. Assuming you want to experiment with different capsules, the best choice is a 22mm wide body. Assuming you also want pad and/or low cut switches and enough space for a transformer, then only the Takstar CM-63 and Alctron T-02A, and maybe Takstar CM-60 come to mind.

Jan

 

[pmfalcman]

What about the capsule side?

Transplant from original PCB.
Hot glue should be sophisticated and sturdy enough

 

[pmfalcman]

Transplant from original PCB.
Hot glue should be sophisticated and sturdy enough

I mean the nose cone. Transplanted from original PCB and glued to the new one.

 

[pmfalcman]

Or, as Jan subtly suggested, restrict the PCB sizing to Alctron and Takstars.
The board for CM-60 and 63 can be one, trimmable, with long traces at the XLR end. And a line marking the cut.
One has a 63? They use full length. For the 60 one just cuts the board at the line.
Maybe the same would work for Alctron. I know nothing about them.

 

[MicMaven]

employ your idea of mounting on stiff wires but from the XLR side.

Serving Suggestion No. 203899

Alternatively, I sometimes just cover the PCB with a length of heat shrinking tube and let it float inside the body with a some fiberfill, foam or other packing material that sorta, kinda, almost dampens body vibration. Your mileage may vary. James

 

[jp8]

Or, as Jan subtly suggested, restrict the PCB sizing to Alctron and Takstars.
The board for CM-60 and 63 can be one, trimmable, with long traces at the XLR end. And a line marking the cut.
One has a 63? They use full length. For the 60 one just cuts the board at the line.
Maybe the same would work for Alctron. I know nothing about them.

I have the CM-60, CM-63 and T-02A. Switches are on different locations. If you intend to use those, then a universal PCB won't work. If you also appreciate an effective RFI filter, I think it will only work well when placed next to the XLR and following proper RF PCB layout guidelines.

Jan

 

[jp8]

Don't want to hijack Khron's thread, but if there is interest, I wouldn't mind designing such PCBs. But I'm not sure whether I can use Jules' OPA circuit for that. I would be *very* upset if someone would copy my designs and make money out of it while I spent a lot of engineering effort in optimizing the circuit design. I know we're all doing this, copying legacy designs which are no longer active products, but Jules is still alive and kicking, selling his OPA designs in various ways. I'd rather use one of my proprietry circuit designs, but then it will not be an open source project. Or I could use an improved KM84 circuit, which I don't want to claim as a proprietry circuit and for which I can (and later will) publish the circuit diagrams.

But if this would be another one of Khron's PCBA projects, it's fine with me. As I said, I don't want to hijack this thread or Khron's project. Just want to offer my "services" in case Khron has no intention to offer SDC PCBs.

Jan

 

[Khron]

But if this would be another one of Khron's PCBA projects, it's fine with me.

It may well end up being one. I do actually have a pair of CM60's to work with, so one of these days...

But not before finishing moving house, settling in, and so forth. And assembling & testing at least one of each of the boards / projects already on this list, etc

 

[nyystero]

Highly interested in ORS87-Plus boards if you ever happen to stock some and ship in FI

 

[untamedfrontier]

If any testing is needed on the Fet847 multipattern, I'd be interested in helping. Otherwise I'll just wait for the boards to be available

 

[Khron]

ORS87-Plus updated to v1.1 - added the "calibration" input & associated 560 ohm resistor; PCBway project, Mouser / Digikey BOMs and toner-transfer / DIY-etch files updated accordingly

Not that one couldn't add the 560 ohm resistor in series with the 10k and use the "aerial" solder joint as the "cal" input, but might as well make it (more) elegant..?