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Re: Alternatives to Soma Ether V2

 

What an interesting thread. While going down a reddit-rabbit-hole on the Soma Ether, I fell across a link to . Similar to the ideas in this thread, it is a sort of "crystal radio" for EMI.? (Ok, it's actually a crystal radio, and would receive AM stations with the right inductor/capacitor combination). So, yet another way to pull some interesting audio from the RF and EMI around us.
Re: Alternatives to Soma Ether V2

 

Great info on this thread. I have some documentation of electromagnetic listening here: including a link to my favorite solution: "telephone pickup coils" are iron core coils with suction cups on them, pre-wired to a 3.5mm mono plug. I buy them for , chop off the plugs, and solder them into pairs for stereo. Way too much fun for such low effort!

But remember, all of these coil-based pickups are based on simple induction. There's no rectification going-on, so they are limited to human bandwidth (20-20k) and close range. You asked about the Soma Ether, which is different because, as they say on the Soma website:?
ETHER is not just an inductive sniffer like some projects you can easily find online. A simple low-frequency inductive sniffer will be silent in most places that are full of sounds in the video. Such devices need to be placed close to an emitting source and will not work on a street. All they contain is a coil and a low-frequency amplifier. In comparison, ETHER has a regenerative circuit and a demodulator, making it an actual radio wave receiver, not just an amplifier of low-frequency magnetic fields. However, ETHER can perceive the low-frequency magnetic fields as well. But, honestly, if your goal is to scan objects in close proximity (0-20 centimeters), a simple inductive sniffer will work cleaner and more focused due to its narrow band and lower sensitivity. ETHER was designed to be a part of your walks in the city and may even pick up sounds in a forest or at the seashore (I have such experience). Also, ETHER can perceive the electric component of the radiation as well, capturing radiation that is far above the audio range and is much more sensitive. Therefore, it has a significantly different design, functions and implementation than a simple inductive sniffer even if in some cases their functions can overlap.
With that said, I have borrowed a Soma Ether from a friend and found that in urban locations it was mostly overwhelmed by rather static buzzing textures (likely from Wifi) regardless of the settings or orientation. It is very sensitive, so this constant sound mostly swamped the local inductive fields I was interested in. I didn't try it in a more off-grid location, though. Your mileage may vary.
Re: Alternatives to Soma Ether V2

 

I missed the beginning of this thread, so this might be unhelpful, but what about using a guitar pickup? (single coil obv) there are loads of cheap pickups out there that may be so-so for guitar use put provide a coil (or two) with 10k winds or more for not much money.

They are infamous for picking up EMI

remove the magnets, use a high impedance input and either pick one that already has iron slugs as polepieces or install your own ferrite core as the shape of the coil and bobbin permit?

they are quite sensitive to capacitance, so you'd want the electronics close to the coil and probably several Mohm input impedance.
Re: Alternatives to Soma Ether V2

 

Le 29/05/2024 ¨¤ 10:53, goldenhours_71 a ¨¦crit?:
These had much less windings but still picked up some very interesting sounds, I think because of their larger diameter. Generally, they seem more 'omnidirectional' than the little ferrite core inductors.
Ferrite or ferromagnetic cores concentrate magnetic field. It's what make them more sensitive compared to a coreless inductor of same size and turn number.
Since lines are concentrated directionality is increased.
Anyway this type of antenna is inherently directional.


I remember using an inductor calculator at the time:
Inductance is almost irrelevant, unless you want to tune the antenna for a certain frequency range, but it's probably not the case. You want to receive base band signals, in the audio range.
Increasing the turn number increases the received signal, to a limit where the increased impedance creates a low-pass filter with the preamp's input impedance.


Would some of the ham radio enthusiasts in this group care to chime in? Perhaps they can provide some insights on how to 'tune' these kind of devices.
This has nothing to do with radio, it's audio bandwidth. Tuning the circuit, by adding a capacitor in parallels would result in a band-pass filter. It would be useful only if you ant to pinpoint one frequency range at the detriment of others.
Re: Alternatives to Soma Ether V2

 

@dimento454 you simply solder the two inductor terminals to a desired length microphone cable and put a plug at the other end, which connects to your preamp/recorder/mixer (minijack/jack/XLR).
It's good soldering practice since the part is fairly forgiving in case it gets a bit too hot. Unlike little electret mic capsules which fry very easily...

@underwood it's been at least 10-15 years ago since I experimented with this, and I can't claim to have gained much knowledge through systematic testing since I was happy with the sonic results very quickly.
I was inspired by Christina Kubisch's electrical walks. I tried both very thin wire gauges, like around 0.1mm or even less, with around 100 to 200 windings on a piece of 4-inch pvc pipe.
I was also gifted a huge roll of 1mm wire at the time, and built a simple 'weaving frame' to make larger diameter antennas like they used to make for radio communications.
These had much less windings but still picked up some very interesting sounds, I think because of their larger diameter. Generally, they seem more 'omnidirectional' than the little ferrite core inductors.
I remember using an inductor calculator at the time:
Some photos of what's left of these experiments here: /g/MicBuilders/files/DIY%20Inductors

Would some of the ham radio enthusiasts in this group care to chime in? Perhaps they can provide some insights on how to 'tune' these kind of devices.
Despite the fact that we're looking to capture here is the very EMF interference that they're trying to reduce ;-)

D
Re: Alternatives to Soma Ether V2

 

Hello,

I've tried different inductors and I had the best results with these tiny 22mH inductors.

@David can you give some more information about your air conductor? Dimensions, number of windings and wire gauge? Better range and sensitivity than the simple inductor?

greets
´³¨¹°ù²µ±ð²Ô


Am Mi., 29. Mai 2024 um 08:02?Uhr schrieb dimento454 via <damiandrohan=[email protected]>:

On Tue, May 28, 2024 at 09:46 PM, goldenhours_71 wrote:
Thanks David. I'll take a look. My hesitation is mostly about my assembly ability. I have put together a few of those mini electronics practice kits, so maybe I should take it up a notch. Appreciate your help, D

Re: Alternatives to Soma Ether V2

dimento454
 

On Tue, May 28, 2024 at 09:46 PM, goldenhours_71 wrote:
https://ie.rs-online.com/web/p/leaded-inductors/7157267
Thanks David. I'll take a look. My hesitation is mostly about my assembly ability. I have put together a few of those mini electronics practice kits, so maybe I should take it up a notch. Appreciate your help, D
Re: Alternatives to Soma Ether V2

dimento454
 

Thanks @Jonas. I have looked at the schematics before but ruled them beyond my ability to make, I'll have to have another look. I have a set each of your USI and Micro USI and they're great. Thanks for your response
Re: Alternatives to Soma Ether V2

 

PS search for images with "frame antenna" for design inspirations :-)
Re: Alternatives to Soma Ether V2

 

Plus one for Elektrosluch! It's a simple clean headphone preamp and can be built from the available schematics.

The cheapest option, if you have a mic preamp (in your recorder or mixer) is to simply solder a cable to a leaded inductor with ferrite core (for example ).
Anything around 15-30mH will work. Get a few different values and experiment.

I also got some very interesting results with winding my own air core inductor coils. All you need is enamel coated copper wire. This supplier in the UK has a great selection of different gauges:

Greetings from Westmeath!

David
Re: Alternatives to Soma Ether V2

 

¿ªÔÆÌåÓý

Hi there,
Jonas from LOM here. All Elektrosluch designs are open-source and you can look them up on our github (LOM-instruments). Or we do sell Elektrou?i which are passive sensors that work with mic-in inputs on portable recorders.
Regards,
Jonas

On 28 May 2024, at 10:53, dimento454 via groups.io <damiandrohan@...> wrote:

?Morning all and greetings from Cork. I'm just wondering if any of you have tried the Soma Ether V2, what it's like? Also- are there alternatives that can do something similar for less money- I can do basic soldering and assembly so maybe if there's a DIY kit?

I had my eyes for a long time on the LOM DIY Electroslusch mini city. I know they're not exactly the same, but that kit seems to be discontinued.

I have read that the Soma picks up amazing sounds, but also some concerns about the build quality. I know it's not a lot of money but I'm always reluctant to buy things that might not last a reasonable amount of time.

Thanks in advance

D

Alternatives to Soma Ether V2

dimento454
 

Morning all and greetings from Cork. I'm just wondering if any of you have tried the Soma Ether V2, what it's like? Also- are there alternatives that can do something similar for less money- I can do basic soldering and assembly so maybe if there's a DIY kit?

I had my eyes for a long time on the LOM DIY Electroslusch mini city. I know they're not exactly the same, but that kit seems to be discontinued.

I have read that the Soma picks up amazing sounds, but also some concerns about the build quality. I know it's not a lot of money but I'm always reluctant to buy things that might not last a reasonable amount of time.

Thanks in advance

D
Re: BJT models for LTSpice

 

MAT02 and ZTX1048 are in the standard LTspice library; they're npn's.

Le 26/05/2024 ¨¤ 14:58, David Pickett a ¨¦crit?:
Can anyone direct me to models of low noise discrete (not surface mount!) transistors (e.g. BC109 type) for use in LTSpice, please?

Many thanks,

David
Re: BJT models for LTSpice

 

Just as a bit of fyi... If you are after the lowest possible noise BJT, PNP will get you a lower theoretical minimum noise than NPN. As a differential matched pair, the SSM2220 used to be the benchmark. The NPN version (not quite so super quiet) is SSM2210
Glenn


On Sun, 26 May 2024, 1:58 pm David Pickett via , <dhp=[email protected]> wrote:
Can anyone direct me to models of low noise discrete (not surface
mount!) transistors (e.g. BC109 type) for use in LTSpice, please?

Many thanks,

David
BJT models for LTSpice

 

Can anyone direct me to models of low noise discrete (not surface mount!) transistors (e.g. BC109 type) for use in LTSpice, please?

Many thanks,

David
Re: Contact Microphone advice

 

Great, thanks for the affirmation Jules.
I just ordered some piezo discs (including the ultrasonic 35W) and a little batch of 2SK170-GR I found from a local (DE) seller by chance.

Regards,
Domingo
Re: Contact Microphone advice

 

¿ªÔÆÌåÓý

Those discs work great, if you can find them. The key is shielding and the piezo buffer. You Pip with higher voltage and resistor should work. The current through the FETvwill be similar thus the 150ohm resistor bias should still work.?
Best Regards,

Jules Ryckebusch?

On May 25, 2024, at 07:43, Domingo Riesco via groups.io <chumariesco@...> wrote:

?Thank you Zach! So good that you documented and share your knowledge and experience.

I'd like to try the FET buffer, I never built one but it seems simple as the guts of my electrets :). My 'PiP' is ca.11V through a 20K resistor, which provides 0.5mA; instead of the standard 2.5V through 2.2K that your circuit is based on. I might have to replace the 150ohm drain resistor with something higher or try other JFETs, no experience on that as I said. BTW, maybe you confused drain and source in your text description of circuit¨Cit seems to me that the 150ohm is a source resistor and the drain resistor is 'inside the recorder' (counter-intuitive).

I like your take on ultrasonic piezo discs, for flatter response. I suppose that they should be as big as possible and the resonant frequency not that far beyond the audible spectrum, to keep them sensitive. Some are 50mm with resonance at 40kHz, but rated 35W :s so not sure how they would sound.

is also interesting, with a higher resonant frequency than the LOM but unfortunately half sensitive.

Cheers,
Domingo

Re: Contact Microphone advice

 

Thank you Zach! So good that you documented and share your knowledge and experience.

I'd like to try the FET buffer, I never built one but it seems simple as the guts of my electrets :). My 'PiP' is ca.11V through a 20K resistor, which provides 0.5mA; instead of the standard 2.5V through 2.2K that your circuit is based on. I might have to replace the 150ohm drain resistor with something higher or try other JFETs, no experience on that as I said. BTW, maybe you confused drain and source in your text description of circuit¨Cit seems to me that the 150ohm is a source resistor and the drain resistor is 'inside the recorder' (counter-intuitive).

I like your take on ultrasonic piezo discs, for flatter response. I suppose that they should be as big as possible and the resonant frequency not that far beyond the audible spectrum, to keep them sensitive. Some are 50mm with resonance at 40kHz, but rated 35W :s so not sure how they would sound.

is also interesting, with a higher resonant frequency than the LOM but unfortunately half sensitive.

Cheers,
Domingo
Re: Contact Microphone advice

 

Hi. I started a table of info about contact mics and preamps on my website. I use them to record tiny things (rather than mic louder instruments) so maybe the research will be useful for you too?

Example: Here's my low-tech but extremely low noise preamp that works with plugin power:

-Zach
Re: Contact Microphone advice

 

Thanks for the replies.
What contact microphones are mostly being used by the community and which specs should I consider?
I see many in offer for musical instruments, like the Korg CM-400, or many unbranded for guitars on Ali and so on. But none indicate sensitivity (dB/mm?) or frequency response charts.

JrF seems C-series like the most reliable option, right? I just wonder which alternatives are there or how different from typical 20EUR instrument contact mics it is. For well, last time I ordered from UK to continental Europe I paid a leg in taxes (sorry to mention that).

Cheers!
Domingo
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