Has anybody given this a shot with an audio interface or a TX-6? I just tested and it seemed like I needed to boost the gain quite a bit. Like, I need +11 gain. Does this sound right?
I must admit tho, the audio is bizarrely clean af!
EDIT: I think when I put it in to the aluminum tubing, I created a short for the battery against the tube, either causing problems for the battery or shorting out my op amp. I will try a different battery when I can. If that doesn’t fix it, I will try reflowing the amp and lastly replacing it.
Fingers crossed
Durdee
67
I’ve used mine for several applications and depending on the use case, I’ve definitely needed to crank the gain on whatever preamp I’m running it into. But this makes sense, the circuit on the board gives you the cleanest signal you can get from the specified capsule and then when you’re adding gain after the fact, you’re getting the lowest s/n ratio possible.
Best of luck with the fix! I’m supposed to receive a couple of the smaller sized boards tomorrow and I was curious about how to best solder those to keep them from shorting… not sure if the board is exactly 6mm across or if you could fit a bit of heat shrink over the wire end, that would keep things from shorting out and would also provide a bit of strain relief at the same time.
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I’m thinking kapton tape would be just fine to prevent the short in the future. I did have like, a solid signal going in to my M8 before this recent gaff of mine.
I’m curious, do you have a Norns? Like, I can’t put it in to the Norns and hear much signal. It seems too low to be right. I’ll test another battery tho
Durdee
69
Sadly, no Norns (yet, anyway!). Mostly been plugging mine into my modular to mic random noisemakers on my desk. It sounds like there may be something wrong, but also if your battery shorted out to the case it may have just died really quickly.
Oh… that absolutely could be it. 
I hope to have time in the next hour or so to check.
Oh, it’s deffo the amp. I blew it out. Glad I have a bunch more.
EDIT:
Okay, so, I have built another and while it works, it’s so quiet that it’s essentially unusable. I have tested the battery, the audio connection, I have put it through to other interfaces and devices….
Having a second one that has experienced this means I’m essentially going to back out of the project. A real bummer as these seemed exciting!
NEW EDIT:
IC names suck. Somehow got the wrong ones. Will salvage the boards and keep building eventually.
Durdee
71
Just burned out my first tiny board. I have yet to pull it back apart to see what went wrong, but the end of the mic tube got a bit warm and then that was that. Battery died. Hmm……
I got some Kapton tape for when I revisit the build to keep the battery wires/contact points away from the tubing. That seems to be the most likely point of contact and shorting
Love this project so much but I needed something stereo for my Clippy EM272 stereo pair so I designed a stereo version using the reference design you provided but changed all the values to work just right for the EM272Z1 capsule. Using some cheap extruded aluminum boxes and printed pcb’s as ends. The sound is so clear, so much better than when I have used them through some cheap field recorders in the past. I added the ability to bring in dual mono and input dual mono as well.
32 Likes
Lovely recording!
Wow those EM272s are specced extremely well. -28dB sensitivity at 80dB S/N.
What values did you use to suit the capsules? I may have to try some for myself if I can get the capsules. Seems like Primo, while being a Japanese company, don’t actually sell their capsules in Japan, only finished products.
1 Like
I’m in the states and had to purchase some European ones. Odd.
forrest
77
Thanks!
I’ve put everything in a github repo so you’re welcome to it. Lom’s Uši Pro uses the same capsule, so this design should work for them as well.
As an aside, this box seems to work OK running my LOM Elektrouši (I don’t think these are supposed to use plug-in-power) Here is a recording of my 128 grid (the device itself) running ‘Awake’ through these stereo electromagnetic mics (with 10k+ rolled off, there was some high frequency noise)
13 Likes
I’m sorry to bug ya again. But, I seem to be finding a heck of a time finding the file that details the placement of all the parts. Could you fill me in on what I’m overlooking?
Hello! No problem at all.
For each version of the board, in the BOM folder there should be an HTML file called “ibom.html” - that will bring up an offline webpage which has all the components and their locations. Hope that helps!
4 Likes
That was it! 
Thanks for the help and quick response!
::edit::
@kasselvania Which part did you buy that was incorrect?
I believe I may have done the same thing. I got it all soldered and put together last night, powered it up, but the volume is incredibly soft.
2 Likes
I incorrectly purchased this amp:
OPA172IDBVT
While I should’ve (and eventually did) purchased this:
OPA172IDCKR
The way that I could tell that they were incorrect was that the first one was actually too big for the footprint for the IC on the PCB.
Even after having the correct part, The mic didn’t initially work! I had to reflow all the contact points and found a faulty one. The tiny mic pre is TINY and is a bit tough to build, even though there are very few components.
2 Likes
Yeah the tiny version isn’t the friendliest thing ever.
The regular version is tricky enough for people who don’t have experience with SMD - it requires a bit of thought about the order you place components so as not to make it really hard to get your iron in to solder the last components. The tiny version is even less forgiving, however.
To add to this, I suggest anybody building the tiny mic pre, GET KAPTON TAPE!
It’ll help give security so that the wire joints don’t happen to touch the aluminum tube and cause a short!
2 Likes
Hello! I looked over your schematic, I think I have all the right components. Any chance you’d be able/willing to look it over and tell me if it’s correct before I place the order?
::Edit::
Forgot the link.
https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=e26bbc3bf6
Is this for the tiny version?
I see you’re missing the electret microphone and also some of the parts are the wrong size.
There’s a cart linked on the Github page with the right bits:
https://www.mouser.jp/ProjectManager/ProjectDetail.aspx?AccessID=1ea3a70ac9
Hope that helps!
By the way, the opamps are on backorder from Mouser but can be sourced from LCSC and perhaps some other places.
3 Likes
Actually, I put together one of each of your layouts. I was blown away by the clarity of that electret mic! But I meant @forrest layout. Yours were such fun builds, I thought I’d take a crack at their build too! Accidentally dropped a couple op amps in the process though. 
1 Like
