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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!?
Re: Parallel capsules with simple p48

 

¿ªÔÆÌåÓý

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 :)? ??
Parallel capsules with simple p48

 

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: Alctron MA-1 Schematic question

 

¿ªÔÆÌåÓý

The MA1 circuit is a blatant rip-off of the Triton Fethead version 2, which is marginally less bad than the version 1.

Le 13/02/2025 ¨¤ 12:06, Jerry Lee Marcel via groups.io a ¨¦crit?:

Isn't the cascode an inverter?

Le 13/02/2025 ¨¤ 11:37, Goran Finnberg via groups.io a ¨¦crit?:
The schematic is in error.

XLR1 Pin 3 goes to XLR 2 Pin 2.

XLR1 Pin 2 goes to XLR 2 Pin 3.

This implies that we get a polarity shift.

Very bad design indeed.

Is this really the original schematic or a fake copy.


.........


Best regards,

Goran Finnberg
The Mastering Room AB
Goteborg
Sweden

E-mail: mastering@...

Learn from the mistakes of others, you can never live long enough to
make them all yourself.??? -?? John Luther

(\__/)
(='.'=)
(")_(") Pyret, Ranglet, Aron, VovVov, Nero, Smurfen & Pussin:RIP
Re: Alctron MA-1 Schematic question

 

¿ªÔÆÌåÓý

Isn't the cascode an inverter?

Le 13/02/2025 ¨¤ 11:37, Goran Finnberg via groups.io a ¨¦crit?:

The schematic is in error.

XLR1 Pin 3 goes to XLR 2 Pin 2.

XLR1 Pin 2 goes to XLR 2 Pin 3.

This implies that we get a polarity shift.

Very bad design indeed.

Is this really the original schematic or a fake copy.


.........


Best regards,

Goran Finnberg
The Mastering Room AB
Goteborg
Sweden

E-mail: mastering@...

Learn from the mistakes of others, you can never live long enough to
make them all yourself.??? -?? John Luther

(\__/)
(='.'=)
(")_(") Pyret, Ranglet, Aron, VovVov, Nero, Smurfen & Pussin:RIP
Alctron MA-1 Schematic question

 

The schematic is in error.

XLR1 Pin 3 goes to XLR 2 Pin 2.

XLR1 Pin 2 goes to XLR 2 Pin 3.

This implies that we get a polarity shift.

Very bad design indeed.

Is this really the original schematic or a fake copy.


.........



Best regards,

Goran Finnberg
The Mastering Room AB
Goteborg
Sweden

E-mail: mastering@...

Learn from the mistakes of others, you can never live long enough to
make them all yourself.??? -?? John Luther

(\__/)
(='.'=)
(")_(") Pyret, Ranglet, Aron, VovVov, Nero, Smurfen & Pussin:RIP
Re: What is the role of the capacitor in Simpl48 circuit?

 

Hi Jerry,
You're right, the second one is the simplest48 circuit.
Re: RCA/Shure Model # MI-559156

 

Bob,
?
I have bought some very old and dirty microphones at flea markets or recycling stores. I am not a professional micbuilder, but I am always happy when I can find technical information about the microphones and give them a new life.
?
Btw: I also searched on SHARC's website for 559156, but it seems the RCA handmic PDF is the only information they have.
?
559156 site:https://sharc.net/
?
Heinz
?
On Thu, Feb 13, 2025 at 11:54 AM, Bob W8RMV wrote:

Heinz,
I looked again at the RCA handmic link you sent & think I found the schematic for mine.
It shows an unidentified PNP along with the resistors & cap that is on my mic's board.
?
Thank you again!
-Bob
Re: RCA/Shure Model # MI-559156

 

Heinz,
I looked again at the RCA handmic link you sent & think I found the schematic for mine.
It shows an unidentified PNP along with the resistors & cap that is on my mic's board.
?
Thank you again!
-Bob
?
?
?
Re: RCA/Shure Model # MI-559156

 

Thanx Heinz.

Never thought of searching for a pdf. Duckduckgo didn¡¯t find that.

I did more surgery on it & in the base there is a small amplifier in it.

It has a RCA branded 2N408 germanium PNP that tests good as does the mic cartridge.

It also has a 10uF 15 V cap that surprisingly tests very good for value & ESR.

I imagine 8-12 vdc would be a good supply voltage.

I may reachout to the SHARC¡¯s & see if they have anymore.

Or I may just bypass it to use with my Tempo One transceiver.

?

Thanks again - Bob

?
Re: RCA/Shure Model # MI-559156

 

Hi Bob

When I searched Google for:

"MI-559156" filetype:pdf

Two results came up:

Shure OEM Model Prefixes
PDF
MI-559156. 344A4611. 122037. 209468P3. GE. 559853D1. 99A86. 99B86. Base station, 6418, RCA, 97B140D (444var.?) Condenser, amplified, DTMF, handheld, Ericsson/GE ...

South Hills Amateur Radio Club
RCA ?(Courtesy of the RCA and the RCA 500 Series two-way radio forum.)
MI-559156-(4 COND. STK. #241762) TERM. A, B, C & D. MI-559156-A(6 COND. STK. #241763) TERM. A, B, C, D & F. MI-559156-A1(8 COND. STK. #244033) TERM. A, B, C ...

The RCA500mic.pdf contains some MI-559156 relateded amplifier circuits.?

For more information and if other micbuilders don't have any more details on the MI-559156, you can try contacting the South Hills Amateur Radio Club in Pennsylvania. If you're lucky, they may ask their members for a (copy of) a manual or schematic diagrams. at

Hope this helps!

Heinz?

Am Do., 13. Feb. 2025 um 03:37?Uhr schrieb Bob W8RMV via <W8RMV=[email protected]>:

Greetings,
I've a RCA/Shure Model # MI-559156 that I am trying to find a schematic or user manual for.
This mic looks like a 444 or 444D & has a Shure Brothers sticker on the bottom but has some unique circuit construction in the base.
The mic element has only 2 connections so it is not the 444D element.
There are 3 or 4 resistors & a capacitor inside the base and has black, white, red, green cable wire.
I did search old messages here & the interweb but haven't found anything.
I also contacted Shure to no avail.
This is my last hope!
?
73 Bob
Re: Merging three Capsules on two Preamps?!

 

If you could briefly sketch the schematic you suggested that would be amazingly helpful!
?
I've attached the Primo EM272 datasheet.? Look at the diagram on the right, that's what I'm referring to.? In the place of the 5 volt battery you can use a 9 volt battery and a higher value resistor, say around 6-10k ohms.? You can use the same battery to power all three capsules, each through its own resistor.
?
On the output side, you have an unbalanced signal with plenty of gain for a recorder.? You can put a resistor from the capacitor to your mic input, and if you connect two capsules that way you can adjust the resistor values to set the ratio between the capsules.? Or use a variable resistor, also called a potentiometer, so that you can adjust it while listening.
?
This will work with electret capsules, it does not quite give you the "XLR mic input for a vocal mic" you were referring to.? However, you could build your own vocal mic using a cardioid pattern capsule and this same approach.?
?
-Scott

EM272.pdf
EM272.pdf

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