These sound lovely.Where can I find a pair of these or similar?
https://lom.audio/product/usi/
https://lom.audio/product/elektrosluch-3-plus/
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Electret omni pair : i use the Luhd PM-01 (based in Europe) as a compact travel couple. Works fine, low cost allows to try placements i wouldn’t dare with a 2k€ pair, and to keep them in my daily bag.
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The usi is really nice btw! I have the usi pro with xlr, and that combined with my sounddevices preamp makes is possible to bring out even the most quiet ambiences!
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I subscribed to their list, hopefully they will start producing them again.
Yeah he does a few runs a year so be quick to click when he announce the next run.
Great guy so good to support =)
There is also a Facebook group:
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re: elektrosluche, you may be interested in similar functioning devices, such as the detektor: http://www.1010.co.uk/org/detektor.html
it is not stereo, but can pick up additional frequencies. not sure if there are other differences, would be interested in someone more knowledgeable comparing them.
Have one of these coil pick-up mic’s, great fun, and super cheap. I guess if you know anything about electronics they’re not that difficult to knock together.
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Pickup-coils :
You can also find them for way cheaper on ebay, just look for “telephone pickup coils” (example).
Apparently JrF removes some sort of “limiter” inside them, but specifies that some come already without it… I shall try to open mines, but I believe it really is just a coil. I also bought a pack of 20 really big ones years ago on ebay for next to nothing, but didn’t had time to try those at the moment and now I can’t find them back… 
would have love to hear the differences (I moved a lot of times in between, so they’re most likely lost.)
If you want to DIY it, Gieskes has some information on his website : http://gieskes.nl/undefined/tutorials/?f=inductor-puckup
This one works with a 33mh inductor and a small rare earth magnet, but he also now sells an other one just called “inductor jack” with a 100mh inductor and no magnet (see here & here), conveniently housed in a jack socket.
I’d like to try the LOM take on it though, the extra circuitry should lead to a cleaner signal.
Electrets:
I only hear high praises for the LOM Usis, but it’s been years since I try to grab a pair of them and always miss them when they are available, they’re always sold out in a few hours, and the two last times their website went down.
I’m looking for a great alternative, without succes for now…
I had a look at the Clippy Micropones which uses Primo 172 electret capsules, but they only go down to 60Hz (the Usis go well below that).
I might buy a pair of Luhd ones since they’re quite cheap, to go with my PCM-10 for really light travel, but I’m still looking for an alternative matched XLR pair, any ideas?
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I’ve built a few omni electret mics using cheap panasonic capsules. They are phantom powered and sound great on accoustic guitars. There used to be a mic builders yahoo group that had a lot good info and schematics.
I was going to say pretty much the same as sns.
you can use these:
get great noises when pushed up close to fans and motors. Treat the signal like a guitar signal. It wont power headphones like the elektrosluch does. Not as sensitive as anything with a pre amp - but its pretty much the same set of sounds.
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Co-sign on the JRF coil pickup. Just received mine a few weeks ago (pictured alongside some goodies from the mighty Common Eider, King Eider —it was a good mail day!) and it’s been lots of fun running it through various pedals, usually recording the hum and signal from the pedals’ own power adapters. Seriously thinking about getting another one so I can play around in stereo! Good price as well.
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With non visible radiation being a (continuous) interest of many people, I just wanted to point to these by Gieskes. 100mh inductor mounted nicely to a mono mini-jack.
I’m getting some to use with my MI Ears.
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nice idea. I’ve made some inductors on cables before but this would be much easier and neater, might copy 
Oof, I dig it, but that shipping would wreck me. Maybe I’ll just have to emulate it.
Learning how to enjoy and build my own electret microphones - they sound great and they work well with my ZOOM F1, although their ability to record sounds at further distances is lacking.
I’d like to know if there’s a way to power them via guitar pedal or line booster that runs on a 9V battery and is cheap. I’ve been trying to build preamps and they sometimes work a little bit, but I’d rather have a nice pedal or box that fits in a bag and is cheap. Been looking at field recording mixers, etc. Not cheap.
Can a guitar pedal ‘booster’ work with an electret microphone? Say the Electro-Harmonix EHX LPB-1 boost the signal in a nice way? Any other ideas?
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Alright, I figured it out!
I had these LM386 pre-made amplifier circuit boards. They’re WAY TOO SMALL for me to actually solder together, but they’re cheap and do the trick. I can solder to the pegs by myself, and had a switch, and found a case to hold it.
Here’s what I made out of it:
So, it’s LOUD. Like ‘holy cow’ loud. I suppose it has some ‘noise’, but how much of that is actually just my environment being amplified about me? I live in a noisy part of Tucson, and my backyard is loud.
Here’s an MP3:
I had the knob up at full, then, 75%, then halfway. I had my ZOOM F1 at ‘MID’ for it’s microphone setting, and the PiP turned off. I made the microphone with a Panasonic WM-54BT electret capsule. Nothing else. The birds are 40 feet away. The trucks are 4 blocks away, the airplane is overhead going through rainclouds. The amplifier is running on a 9V battery. The microphone looks like the single head mic in my post above.
You don’t have any pictures of the inside of that box, do you? Or did you find instructions online? I think I could get some use outta that.
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I’ll take one shortly. It’s pretty easy, even for me, who is a klutz with a soldering iron. 
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@pleurodesis Here’s the box I put it in - I had this leftover from many years ago - didn’t need the innards. Fits so firmly, it doesn’t even need screws! I drilled the holes in the bottom plate to make room for the jacks, knob, and switch.
Here’s an overhead, to get the general layout. One thing I did was put the output jack on the right, and the input jack on the left. You can see the curvature of the wiring to adjust for my preference.
Here’s two closer shots, just to make sure you can see how easy this circuit actually is. All you’ll need to get for this are:
- 9V battery
- 9V battery connector
- Two (2) 1/8" input jacks
- One (1) On/Off switch, so the circuit doesn’t suck battery juice
This pre-made circuit is all SMD, so those prongs are pretty much all that I can work with, which is why I bought this. It’s cheap, takes a bit of time to arrive from China, but it is LOUD. It has the power to drive the electret mic, then it just boosts the volume. Relatively clear, but not perfect. It’s like a really nice tape-recorder microphone preamp. I read about how many people do not like the LM386 chip, but it works for me. My ears are noisy, so it sounds like real-life to me 
I’ve got a couple more of these coming my way, and I plan to get a smaller box, use a smaller switch, and to mount the circuit board/knob better (may do that today, anyway). Heck, I might even wire the microphone IN the box, so it’s less gear to carry and/or, I’ll make a mini-mic out of just the metal end of a guitar cable.
I think this circuit is possibly dependent upon the quality of the electret you use. Not like you need to go buy a Primo or a Panasonic, but my WM-54BT sounds really nice to me. If you can hear the backyard recording, it’s what I wanted to hear.
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Nice! I’m gonna grab a couple of those amps just to have on hand. Thanks for the heads up and photos.
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