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Re: PCB for ambisonic mic with 9V power supply

 

On Wed, Feb 19, 2025 at 03:42 PM, David Platt wrote:
The guts now consist of four JLI-240A-T capsules
Do you mean JLI-140A-T capsules? I have a few of those. They're nice.
?
Thanks for sharing your circuit.
Re: PCB for ambisonic mic with 9V power supply

 

See the attached ZIP (KiCAD 8 project with schematic and board layout, Gerbers, and a PDF of the schematic).? It might be suitable for you to use, either as-is or as a starting point for changes.?
?
A couple of years ago I was gifted with a "long past its use-by date" Philips stereo microphone.? The old dynamic elements were (I decided) quite useless by modern standards, and the foam had turned to goo and powder, but the shielded enclosure and stand were nicely built and in great shape.? I decided to experiment, gut it, and rebuilt it as a full-field microphone.
?
The guts now consist of four JLI-240A-T capsules, glued into a 3D-printed holder I built using OpenSCAD.? It's based on a basic pattern I found here in MicBuilders, with a graceful branching Bezier-curve support structure which fits into the screw-locked metal shaft in the microphone base.
?
I decided I did want a proper phantom-powered balanced drive for it, so I implemented one of the standard two-transistor circuits using a small PC-board layout (.86" wide by 1.26" long).? This is small enough that I could place four of them around the support shaft, wire them to the mics and to four (Electronics Flea Market surplus) XLR cables, and fit everything comfortably inside the case and shield.? I laid out the boards to suit the parts I had on hand - all surface-mount except for the two 1 uF film capacitors, for which I used through-hole parts I had handy.? I'm sure the boards could be made smaller, using SMT caps and 0805 or 0603 resistors.? I used BC856 transistors because I had a bunch of them in a samples box;? there are many other types which should work fine.
?
OshPark delivered 6 boards, in about two weeks, for under $11... hard to beat!
?
The result - it works, and with the shield closed there's no detectable hum pickup.? I got distracted by other projects and haven't done anything more than confirm the mic's basic functionality, but considering that it's using a standard sort of circuit and decent capsules I don't expect that there are any horrible surprises waiting (he said, walking confidently towards a cliff :-) )
?
?

ElectretPreamplifier.zip
ElectretPreamplifier.zip

Re: Circuit for PiP EM272

  

Hi
Everything is fine with + capsule on + jack and ground capsule on ground jack.
The assembly of the technical sheet is already inside the recorder

Re: PCB for ambisonic mic with 9V power supply

 

¿ªÔÆÌåÓý

No need to duplicate requests.
SimpleP48 is adequate for balanced lines of less than 20 meters. Does not require PCB's.

Le 18/02/2025 ¨¤ 13:01, martenberger92 via groups.io a ¨¦crit?:

Hi all,

I'd like to build a first order ambisonic 9V electret microphone, that I can travel with.

Balanced outputs is important since I will need cable lengths of 6m and longer.

What are the smallest form factor PCBs available for a project like this?
Are there any SMD based circuits openly available?

Thanks and I wish you all a lovely day!
M
Re: Circuit for PiP EM272

 

¿ªÔÆÌåÓý

The Sony PCM10, as well as all other products that provide PIP, include the protection capacitor and resistor.
Addding them would not have any benefit.

Le 18/02/2025 ¨¤ 10:34, dampfus.hansus via groups.io a ¨¦crit?:

Hello fellow mic builders,
I've soldered some cables to the EM272 capsules, with + to signal and GND to GND. My Sony PCM M10 provides 3V of PiP.?
?
Should I also solder in the circuit from the data sheet, with a resistor from GND to Signal and a capacitor to the Mic in?
If so what are the benefits? Is it true that I could damage the recorder through not filtering the DC voltage?
?
Thank you very much!?
Re: Circuit for PiP EM272

 

PIP power already has the resistor and capacitor internally. You don't?need to add them, just?plug it in to the Sony and you should?be good.?

Jules

On Tue, Feb 18, 2025 at 5:29?AM dampfus.hansus via <dampfus.hansus=[email protected]> wrote:
Hello fellow mic builders,
I've soldered some cables to the EM272 capsules, with + to signal and GND to GND. My Sony PCM M10 provides 3V of PiP.?
?
Should I also solder in the circuit from the data sheet, with a resistor from GND to Signal and a capacitor to the Mic in?
If so what are the benefits? Is it true that I could damage the recorder through not filtering the DC voltage?
?
Thank you very much!?



--
Best Regards,

Jules Ryckebusch

214 399 0931
PCB for ambisonic mic with 9V power supply

 

Hi all,

I'd like to build a first order ambisonic 9V electret microphone, that I can travel with.

Balanced outputs is important since I will need cable lengths of 6m and longer.

What are the smallest form factor PCBs available for a project like this?
Are there any SMD based circuits openly available?

Thanks and I wish you all a lovely day!
M
Circuit for PiP EM272

 

Hello fellow mic builders,
I've soldered some cables to the EM272 capsules, with + to signal and GND to GND. My Sony PCM M10 provides 3V of PiP.?
?
Should I also solder in the circuit from the data sheet, with a resistor from GND to Signal and a capacitor to the Mic in?
If so what are the benefits? Is it true that I could damage the recorder through not filtering the DC voltage?
?
Thank you very much!?
Re: Lom usi circuit vs simple P48

 

Re: TSB2590 alternative?

 

Hey! Sorry I saw your message now. Yes I would love to trade, which primo capsules you have? I'm mostly interested in large diagram condenser ones, but I'm open to possibilities.
How many capsules do you need? I think I have 4 spares?
Let me know!?
If I don't answer you quickly, please send me a mail at ninmiso@....
Bye!
-Simone
Re: Lom usi circuit vs simple P48

 

¿ªÔÆÌåÓý

EM272 and EM273 appear to be exactly the same element with a different wiring. The 2-wire version has higher sensitivity, because of the gain of the FET in common-source mode, when the lower sensitivity of the 3-wire version is the result of the FET being used in common-drain mode.
In simpleP48, the circuit is common-source, so there should be little difference between a native 2-wire capsule and a 3-wire.

However, the Jerry Lee variant allows decreasing gain at teh benefit of max SPL.
This can be done only with a 3-wire capsule (or a Linkwitz modified).

Le 14/02/2025 ¨¤ 20:55, kennjava a ¨¦crit?:

The Primo EM273 is similar to the EM272 but with higher SPL handling (135 dB vs 119 dB). Also, the simpleP48 doc has a few ideas about increasing the SPL headroom of some capsules.
?
The LOM basicUcho have a slightly different capsule mounting (flush, vs the slight rim of the Clippy case), which might account for some of the sound difference. I always flush-mount the omni capsules in my mics.
?
?
Re: Lom usi circuit vs simple P48

 

The Primo EM273 is similar to the EM272 but with higher SPL handling (135 dB vs 119 dB). Also, the simpleP48 doc has a few ideas about increasing the SPL headroom of some capsules.
EM273 is a 3-terminal version of EM272.? ie it is EM272 modified as on page 12 of SimpleP48.pdf dtd 29sep24 for use in SimpleP48RCA.
?
This, with EM273 has MUCH better overload performance and should be used if you are having overload problems.
?
I'm playing with some LTspice sims of SimpleP48RCA and it looks even better than I thought; at least in SPICE world :)
Re: Lom usi circuit vs simple P48

 

The Primo EM273 is similar to the EM272 but with higher SPL handling (135 dB vs 119 dB). Also, the simpleP48 doc has a few ideas about increasing the SPL headroom of some capsules.
?
The LOM basicUcho have a slightly different capsule mounting (flush, vs the slight rim of the Clippy case), which might account for some of the sound difference. I always flush-mount the omni capsules in my mics.
?
?
Re: Lom usi circuit vs simple P48

 

I asked?Jonas about these PCBs a while back, they are proprietary information. He will supply them to you, so may be worth asking if he can do some custom circuits on the same board for you.


On Fri, 14 Feb 2025 at 18:14, martenberger92 via <martenberger92=[email protected]> wrote:
Hi all,

I have a pair of Lom basic Ucho mics, but sadly they clip if I use them on my piano.
So I wanna try myself with capsules that have higher SPL and wanna get the best sound possible out of it of course.

Today I looked inside the Lom basi Ucho mic, and there were quite a few components soldered to the pcb. Has that secret of the LOM circuit already leaked into the public domain?

Cause I find Lom sound better than Micbooser in my humble opinion.

Good weekend!
Lom usi circuit vs simple P48

 

Hi all,

I have a pair of Lom basic Ucho mics, but sadly they clip if I use them on my piano.
So I wanna try myself with capsules that have higher SPL and wanna get the best sound possible out of it of course.

Today I looked inside the Lom basi Ucho mic, and there were quite a few components soldered to the pcb. Has that secret of the LOM circuit already leaked into the public domain?

Cause I find Lom sound better than Micbooser in my humble opinion.

Good weekend!
Re: Parallel capsules with simple p48

 

¿ªÔÆÌåÓý

It's true for sounds that are radiated in the pruimary directivity lobe.
When capsules are spaced less than one quarter-wave, that is verified.

Le 14/02/2025 ¨¤ 05:41, Casey via groups.io a ¨¦crit?:

Thanks! So you're saying the parallel capsule (case of two capsules) does in fact increase SNR by 3dB (in ideal mathematical conditions)? -c

On 2/13/25 20:20, Jerry Lee Marcel via groups.io wrote:

sqrt 2=>3dB, not 1.4. 1.414 =sqrt 2.

Le 14/02/2025 ¨¤ 00:45, Casey via groups.io a ¨¦crit?:

Others will correct me if wrong, but based on what I've read here about this:

With Simplest P48 (capsule + resistor + capacitor) you can indeed parallel the capsules. You use a single resistor/capacitor set, but you cut the resistor value in half for two capsules, to 1/3rd for three capsules, etc.

You can apparently also parallel the entire SP48 circuit off the XLR, which someone suggested might be better for 3 or more capsules.

My notes say "Could theoretically power ~14 in parallel, but CMRR degrades with each capsule (because SP48 loads only one of the 6.81k resistors used in phantom); "in the real world you should be OK putting three or four P48's in parallel" "

Someone on this list (sorry for lack of attribution) also said "Doubling the number of capsules can improve your SNR by 1/sqrt(2). So going from 1->2 improves things by that much. Going from 2->4 does so again. Going from 4->8 does so again. But that's where things get a little iffy. 2 capsules arranged vertically mostly works because most sources are going to be in the plane of the mic so you won't get much in the way of comb filtering between the capsules. By the time you've crammed eight capsules into one spot, it's going to start having a noticeable effect. Also, if you look at what 1/sqrt(2) looks like in dB, it's tiny. It's about a 1.4dB improvement in SNR. I don't know how tight the tolerances are on the Primo or PUI capsules, but you may be able to better that by just picking the best of a batch and using those as single capsules per channel."

There are other considerations, but that about sums it up. :-)

-c

On 2/13/25 15:31, Cram via groups.io wrote:
Hi all,?

First post on here - I've done a search through the group but couldn't find a definitive answer.

I've been mucking around lately with aom5024 capsules to go along with the clippy mics that I have, and have been quite happy with their performance. I've got some as PIP, and I've built some into XLR plugs using the simple p48 circuit to use with a zoom h5, and these also work a treat.

I've seen a few mentions online about the merits of running two or more capsules in parallel, and would like to try this myself. Seems fairly straightforward with the PIP examples online, however I've been overthinking it in regards to the phantom power XLR connection and am now double guessing myself.

My question is:

1) can I use the the same p48 circuit I used for a single capsule, and just wire two capsules in parallel
2) do I do #1 but adjust the cap/resistor values to accommodate the multiple capsules
3) does each capsule require its own resistor/cap?

Thanks in advance guys :)? ??
Re: Parallel capsules with simple p48

 

¿ªÔÆÌåÓý

Thanks! So you're saying the parallel capsule (case of two capsules) does in fact increase SNR by 3dB (in ideal mathematical conditions)? -c

On 2/13/25 20:20, Jerry Lee Marcel via groups.io wrote:

sqrt 2=>3dB, not 1.4. 1.414 =sqrt 2.

Le 14/02/2025 ¨¤ 00:45, Casey via groups.io a ¨¦crit?:

Others will correct me if wrong, but based on what I've read here about this:

With Simplest P48 (capsule + resistor + capacitor) you can indeed parallel the capsules. You use a single resistor/capacitor set, but you cut the resistor value in half for two capsules, to 1/3rd for three capsules, etc.

You can apparently also parallel the entire SP48 circuit off the XLR, which someone suggested might be better for 3 or more capsules.

My notes say "Could theoretically power ~14 in parallel, but CMRR degrades with each capsule (because SP48 loads only one of the 6.81k resistors used in phantom); "in the real world you should be OK putting three or four P48's in parallel" "

Someone on this list (sorry for lack of attribution) also said "Doubling the number of capsules can improve your SNR by 1/sqrt(2). So going from 1->2 improves things by that much. Going from 2->4 does so again. Going from 4->8 does so again. But that's where things get a little iffy. 2 capsules arranged vertically mostly works because most sources are going to be in the plane of the mic so you won't get much in the way of comb filtering between the capsules. By the time you've crammed eight capsules into one spot, it's going to start having a noticeable effect. Also, if you look at what 1/sqrt(2) looks like in dB, it's tiny. It's about a 1.4dB improvement in SNR. I don't know how tight the tolerances are on the Primo or PUI capsules, but you may be able to better that by just picking the best of a batch and using those as single capsules per channel."

There are other considerations, but that about sums it up. :-)

-c

On 2/13/25 15:31, Cram via groups.io wrote:
Hi all,?

First post on here - I've done a search through the group but couldn't find a definitive answer.

I've been mucking around lately with aom5024 capsules to go along with the clippy mics that I have, and have been quite happy with their performance. I've got some as PIP, and I've built some into XLR plugs using the simple p48 circuit to use with a zoom h5, and these also work a treat.

I've seen a few mentions online about the merits of running two or more capsules in parallel, and would like to try this myself. Seems fairly straightforward with the PIP examples online, however I've been overthinking it in regards to the phantom power XLR connection and am now double guessing myself.

My question is:

1) can I use the the same p48 circuit I used for a single capsule, and just wire two capsules in parallel
2) do I do #1 but adjust the cap/resistor values to accommodate the multiple capsules
3) does each capsule require its own resistor/cap?

Thanks in advance guys :)? ??
Re: Parallel capsules with simple p48

 

¿ªÔÆÌåÓý

sqrt 2=>3dB, not 1.4. 1.414 =sqrt 2.

Le 14/02/2025 ¨¤ 00:45, Casey via groups.io a ¨¦crit?:

Others will correct me if wrong, but based on what I've read here about this:

With Simplest P48 (capsule + resistor + capacitor) you can indeed parallel the capsules. You use a single resistor/capacitor set, but you cut the resistor value in half for two capsules, to 1/3rd for three capsules, etc.

You can apparently also parallel the entire SP48 circuit off the XLR, which someone suggested might be better for 3 or more capsules.

My notes say "Could theoretically power ~14 in parallel, but CMRR degrades with each capsule (because SP48 loads only one of the 6.81k resistors used in phantom); "in the real world you should be OK putting three or four P48's in parallel" "

Someone on this list (sorry for lack of attribution) also said "Doubling the number of capsules can improve your SNR by 1/sqrt(2). So going from 1->2 improves things by that much. Going from 2->4 does so again. Going from 4->8 does so again. But that's where things get a little iffy. 2 capsules arranged vertically mostly works because most sources are going to be in the plane of the mic so you won't get much in the way of comb filtering between the capsules. By the time you've crammed eight capsules into one spot, it's going to start having a noticeable effect. Also, if you look at what 1/sqrt(2) looks like in dB, it's tiny. It's about a 1.4dB improvement in SNR. I don't know how tight the tolerances are on the Primo or PUI capsules, but you may be able to better that by just picking the best of a batch and using those as single capsules per channel."

There are other considerations, but that about sums it up. :-)

-c

On 2/13/25 15:31, Cram via groups.io wrote:
Hi all,?

First post on here - I've done a search through the group but couldn't find a definitive answer.

I've been mucking around lately with aom5024 capsules to go along with the clippy mics that I have, and have been quite happy with their performance. I've got some as PIP, and I've built some into XLR plugs using the simple p48 circuit to use with a zoom h5, and these also work a treat.

I've seen a few mentions online about the merits of running two or more capsules in parallel, and would like to try this myself. Seems fairly straightforward with the PIP examples online, however I've been overthinking it in regards to the phantom power XLR connection and am now double guessing myself.

My question is:

1) can I use the the same p48 circuit I used for a single capsule, and just wire two capsules in parallel
2) do I do #1 but adjust the cap/resistor values to accommodate the multiple capsules
3) does each capsule require its own resistor/cap?

Thanks in advance guys :)? ??
Re: Parallel capsules with simple p48

 

Being an astrophotographer also, stacking data to increase SNR is something I'm familiar with, though it's interesting to note your assessment of the dB gain in this situation. Having been reading through Vicki Powys' website and a few others touting parallel capsules, including micbooster themselves, it's been suggested there's an approx.? 3dB increase to SNR and 6dB to sensitivity.
Yeah other members here (Joules and Jerry Lee, not sure who I'm quoting here) have said "The concept is that the audio signal from the capsules is correlated and the def noise is not.? The math part says that adding two capsules gives you a 6dB increase in signal. But the noise only adds 3dB.? Real world is close." So that accords with your 3dB idea, but I'm not sure how to square that with the 1.4dB quote. Perhaps someone here can clarify.

Some other quotes from my notes: "...one must consider the changes in directivity pattern. Depending on the physical arrangement (side by side, colinear, back-to-back...) the results may change significantly. The side-by-side arrangement is the one that gives the best improvement in S/N, but it also results in some narrowing of the pattern at HF, which may or may not be desirable."

-c
Re: Parallel capsules with simple p48

 

Thanks so much for the reply Casey - this is most helpful. I'd figured there shouldn't be any harm in doing #3 (apart from increased parts cost and space for components), but wanted to be sure there wasn't a better way of doing it.

I'm at work right now so don't have my mics in front of me. From memory I had my single capsule p48 5024's running at around 5v and they sound quite good to me. I was thinking of pairing up two capsules per channel to try this out, though I do have enough to do three. Now you've given me some clarification I can do some experimenting.?

Being an astrophotographer also, stacking data to increase SNR is something I'm familiar with, though it's interesting to note your assessment of the dB gain in this situation. Having been reading through Vicki Powys' website and a few others touting parallel capsules, including micbooster themselves, it's been suggested there's an approx.? 3dB increase to SNR and 6dB to sensitivity. In micboosters case it really does appear to be just 2 capsules in parallel like other tinkerers do online. I'll be interested to see the outcome with my mics.?
?

Cheers!?
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