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Re: SimpleP48 -- Polarity

 

"Arjay, if you reverse the capsule connections in a normal ¡°true¡± condenser mic, nothing happens there, either¡­¡­.¡±

"I hadn't realised that... I had always assumed that if you reverse the polarity of the DC to a capsule element, you would reverse the polarity of the signal from it?¡±

From the perspective of the capsule, the polarizing voltage has been reversed, so the output signal polarity reverses. But the signal connections have also been swapped. Double reverse. To the outside world, polarity stays the same. I discovered this the same way you did. I swapped capsule leads, expecting the signal polarity to change and it didn¡¯t.

Jerry, I have seen differing descriptions of electret film and how it is made. In one case, the film is heated in a strong electrical field, and then cooled, leaving the plastic with one side having excess electrons, the other side excess holes. So it is an electret dipole, with a positive side and a negative side. I think the first electret mics used such polyester film for a diaphragm.

The other method uses an electron gun to irradiate a high-temperature insulator, usually Teflon to use the commercial name. In this case, there is no positive side, there is only a trapped cloud of electrons. A monopole. I believe this is usually preferred because of long-term stabilty. Teflon doesn¡¯t hold tension well as a diaphragm film, so it is usually put on the backplate, and Mylar is used for the diaphragm.

If you know of an article describing how electret film is applied in mics, I¡¯d appreciate more information. I¡¯m curious how the film is adhered to the backplate. Glue? Sprayed like paint or powder coat, baked, and then charged? A couple of machined brass backplates I¡¯ve looked at had some tented holes, as if a film was glued over the finished metal and not all the holes were opened afterward. Cheap electret backplates look like they were stamped from pre-coated sheet metal.

Electret film is available in industrial size rolls. For home experiments, electret film is used in some air conditioning filters, and maybe could be liberated for a home brew capsule?

I wondered what the effective ¡°polarizing voltage¡± of an electret is. After all, tiny 4mm electrets whose working capacitance would only be 3 or 4 pF are used in cell phones, and their S/N is acceptable. At the other extreme there are 34mm electrets from Transound and unidentified Chinese companies. Sensitivity isn¡¯t amazing at -40dB or thereabouts. Same as a normal K-67. Apparently, the need to increase spacing between diaphragm and backplate with diameter lowers the effective ¡°voltage¡±. Around 200V for a 6mm capsule, and 60V for 34mm.

I¡¯d like to see someone put electret film on the backplates of a K-12 or K-67. Could such a high quality capsule be built with the extra layers? It would have to be built with insulated double backplates to allow pattern switching. All of the existing electrets make the backplate connection from the middle at the back instead of the side, so back-to-back cardioid construction isn¡¯t possible. All of them use plastic acoustic filter / delay plates on the rear, and none sound like the classic 34mm capsules from AKG or Neumann.

As fixed cardioids, they sound good, with their own signatures. Worth experimenting with. I have used RK-99s on acoustic bass and pipe organ with nice results. The cheap ¡°brass covered¡± 34mm capsules are good for some vocals and I¡¯m still trying them on other stuff.



and following blog posts.
P48 Phase Testing with impulses

 

I recorded a couple handclaps and snap sounds with the SimpleP48 wired with pin3 to the capsule "+" and this is the resulting waveform.?




--
Best Regards,

Jules Ryckebusch

214 399 0931
Re: Where to buy electronics parts in the EU

dimento454
 

thanks again all for the links and suggestions

@adrian- yes I buy from Nick at micbooster all the time, v helpful and excellent service
Re: SimpleP48 -- Polarity

 

¿ªÔÆÌåÓý

Sorry to contradict you on some points.
You cannot compare directly a standard externally polarized capsule with an electret capsule.

First because the former is parallel-fed, while the latter is series-fed.
Then you must consider that the traditional polarity of a true condenser is conditioned solely by the polarity of the bias voltage.
A positive pressure on the diaphragm results in a negative pulse only when the bias voltage is positive.
See what happens with the rear capsule in variable pattern mics when put in figure-8 position.

Most electret mics are built with the negative side of the electret facing the diaphragm. A positive pressure puts the diaphragm closer to the electret, which results in a negative pulse. After being reverted by the FET, it results in a positive output.
It is also consistent with the constant charge principle; when the capacitance increases, the negative voltage impaired on the diaphragm decreases.

Le 24/12/2023 ¨¤ 23:56, Henry Spragens via groups.io a ¨¦crit?:

Arjay, if you reverse the capsule connections in a normal ¡°true¡± condenser mic, nothing happens there, either.

Electrets are weird. It took some experimentation for me to figure out how an electret capsule behaves. My greatest confusion is around polarity of the signal generated. Does the electret act like a constant charge on a variable capacitor, same as a ¡°true¡± condenser? Or does the effective charge vary as the diaphragm moves into and out of the electret field?

It appears the ¡°charge¡± increases as the diaphragm approaches the electret film, so this isn¡¯t a constant charge Q = CV situation, where if C goes up, V must go down. What is the voltage, anyhow? If you measure at rest, despite the constant electric field, there is no voltage between the electrodes. And what is the charge, Q? If you put a meter from diaphragm to backplate, no current will flow. Is charge zero? Thinking in these terms wasn¡¯t getting me anywhere.

That¡¯s why I think in terms of electrons migrating. We have a bunch of electrons trapped in a plastic film, which create a negative electret field around the backplate. Bring the diaphragm into the electret field, and electrons from the diaphragm will be repelled to ground, so the diaphragm acts as if it is positively charged. Bring the diaphragm closer, and the field and ¡°voltage" increases. So does the capacitance, incidentally. Both effects increase the apparent negative ¡°charge¡± on the backplate, which causes current to flow across the gate resistance of the FET, driving it negative. As the gate goes negative, the drain goes positive.

And that¡¯s how I explain it to myself. If it turns out my Neumann, Shure, and AKG mics are wired backwards, or I¡¯ve made a stupid mistake, I¡¯ll have to revise my explanation. 8^) 

At least all my mics match, which is the important thing. Including Jules' OPA Alices with RK-12 capsules, which are outstanding mics, BTW.

Re: Where to buy electronics parts in the EU

 

I buy my cables at Thomann. Mostly "Summer Cable" or Mogami from ebay.


Am Mo., 25. Dez. 2023 um 10:26?Uhr schrieb Ralf R Radermacher via <fotoralf=[email protected]>:

Am 25.12.23 um 09:16 schrieb underwood via :
> I buy most of my stuff at Reichelt Elektronik.

They're fine. Just stay away from their cheap cables. Two strands of
wire aren't a sufficient screening and I've had the connectors literally
fall off on several occasions.

Ralf

--
Ralf R. Radermacher? -? K?ln/Cologne, Germany
Blog? :
Audio :
Fotos :






Re: Where to buy electronics parts in the EU

 

Am 25.12.23 um 09:16 schrieb underwood via groups.io:
I buy most of my stuff at Reichelt Elektronik.
They're fine. Just stay away from their cheap cables. Two strands of
wire aren't a sufficient screening and I've had the connectors literally
fall off on several occasions.

Ralf

--
Ralf R. Radermacher - K?ln/Cologne, Germany
Blog :
Audio :
Fotos :

Re: SimpleP48 -- Polarity

 

¿ªÔÆÌåÓý

For as far as i know, and you said it already, the electrons are trapped in the electret, so it is impossible for them to move. So you cannot measure anything. Not by a multimeter or something like that. But there is a charge in the electret. And the charge will not change, the rule Q=VxC is not relevant, for this is not a normal capacitor consisting of 2 plates. I consider a normal capacitor as a special case of handling static electricity.

And look what is happening in the di?lektricum of a standard capacitor. This isolator acts also with opposite charges on both sides of it. Here is also no electron movement possible, the electrons in the atoms are forced to move within the atoms themselves and are able to create a bigger capacity compared to plain air. All is about static charge. We call it static, for it cannot move dynamically.

Just my 2 cents

Henry Spragens via groups.io schreef op 2023-12-24 23:56:

Arjay, if you reverse the capsule connections in a normal ¡°true¡± condenser mic, nothing happens there, either.

Electrets are weird. It took some experimentation for me to figure out how an electret capsule behaves. My greatest confusion is around polarity of the signal generated. Does the electret act like a constant charge on a variable capacitor, same as a ¡°true¡± condenser? Or does the effective charge vary as the diaphragm moves into and out of the electret field?

It appears the ¡°charge¡± increases as the diaphragm approaches the electret film, so this isn¡¯t a constant charge Q = CV situation, where if C goes up, V must go down. What is the voltage, anyhow? If you measure at rest, despite the constant electric field, there is no voltage between the electrodes. And what is the charge, Q? If you put a meter from diaphragm to backplate, no current will flow. Is charge zero? Thinking in these terms wasn¡¯t getting me anywhere.

That¡¯s why I think in terms of electrons migrating. We have a bunch of electrons trapped in a plastic film, which create a negative electret field around the backplate. Bring the diaphragm into the electret field, and electrons from the diaphragm will be repelled to ground, so the diaphragm acts as if it is positively charged. Bring the diaphragm closer, and the field and ¡°voltage" increases. So does the capacitance, incidentally. Both effects increase the apparent negative ¡°charge¡± on the backplate, which causes current to flow across the gate resistance of the FET, driving it negative. As the gate goes negative, the drain goes positive.

And that¡¯s how I explain it to myself. If it turns out my Neumann, Shure, and AKG mics are wired backwards, or I¡¯ve made a stupid mistake, I¡¯ll have to revise my explanation. 8^)

At least all my mics match, which is the important thing. Including Jules' OPA Alices with RK-12 cap
Re: Where to buy electronics parts in the EU

 

Conrad is very expensive. I buy most of my stuff at Reichelt Elektronik. They sometimes have PUI-Audio capsules in stock.



Am So., 24. Dez. 2023 um 17:39?Uhr schrieb ilya dontsov <ilya.dontsov@...>:

TME electronics is another source. I believe they are based in Poland.

Re: SimpleP48 -- Polarity

 

I was going to write a paper on this but there is a definitive discussion of this subject by Lipshitz and Vanderkooy in?"" J. Audio Eng. Soc ., vol. 30, 1982).?
Da Dynamic Duo (L & V) wrote that in response to??which I discussed with Stan at Hamburg.? The AES paper is reduced from the?original which DID report DBLTests which showed audibility of phase on certain test signals.? But as these signals could only be listened for 10min without leaving the victim with a severe headache, I didn't think they were relevant for speaker designers.

The L&V 1982 paper was IMHO, the first proper DBLTs which reported audiblity on Music (actually Vocal) signals.? I don't agree with all their findings but sorta agree on the frequency range of max audibility.

IMnotsoHO, my DBLT panel was better than da Dynamic Duo's. :)
Re: SimpleP48 -- Polarity

 

On Sun, Dec 24, 2023 at 10:56 PM, Henry Spragens wrote:
Arjay, if you reverse the capsule connections in a normal ¡°true¡± condenser mic, nothing happens there, either.......

I hadn't realised that... I had always assumed that if you reverse the polarity of the DC to a capsule element, you would reverse the polarity of the signal from it?
I had thought that was how you use a positive - or negative - DC bias to differntiate between omni and figure of 8 patterns? -- as with
Think I must be getting mixed up a bit?....
Re: SimpleP48 -- Polarity

 

Arjay, if you reverse the capsule connections in a normal ¡°true¡± condenser mic, nothing happens there, either.

Electrets are weird. It took some experimentation for me to figure out how an electret capsule behaves. My greatest confusion is around polarity of the signal generated. Does the electret act like a constant charge on a variable capacitor, same as a ¡°true¡± condenser? Or does the effective charge vary as the diaphragm moves into and out of the electret field?

It appears the ¡°charge¡± increases as the diaphragm approaches the electret film, so this isn¡¯t a constant charge Q = CV situation, where if C goes up, V must go down. What is the voltage, anyhow? If you measure at rest, despite the constant electric field, there is no voltage between the electrodes. And what is the charge, Q? If you put a meter from diaphragm to backplate, no current will flow. Is charge zero? Thinking in these terms wasn¡¯t getting me anywhere.

That¡¯s why I think in terms of electrons migrating. We have a bunch of electrons trapped in a plastic film, which create a negative electret field around the backplate. Bring the diaphragm into the electret field, and electrons from the diaphragm will be repelled to ground, so the diaphragm acts as if it is positively charged. Bring the diaphragm closer, and the field and ¡°voltage" increases. So does the capacitance, incidentally. Both effects increase the apparent negative ¡°charge¡± on the backplate, which causes current to flow across the gate resistance of the FET, driving it negative. As the gate goes negative, the drain goes positive.

And that¡¯s how I explain it to myself. If it turns out my Neumann, Shure, and AKG mics are wired backwards, or I¡¯ve made a stupid mistake, I¡¯ll have to revise my explanation. 8^)

At least all my mics match, which is the important thing. Including Jules' OPA Alices with RK-12 capsules, which are outstanding mics, BTW.
Re: Where to buy electronics parts in the EU

dimento454
 

wow, thanks so much for the lightning quick responses. Oodles of choice there, thanks and happy xmas to all

D
Cheap mic body donors

 

The latest ZRAMO TH900 donor mics I bought from Amazon (BM-700 bodies and circuit boards with 1¡± CM-012 electret capsules) worked out of the box for once. Still ¡°outa phase¡± with a Neumann, but otherwise wired correctly.?A bit noisy by pro standards. This time, came in a glossy printed box with die-cut foam. Included a $11 metal shock mount and foam wind screen. $18 today. Deal.
?
The ZRAMO ¡°104¡± style mics are sturdy metal handheld bodies. The 16mm capsule is OK. The circuit board is good for scavenging an FET or a 3-pin XLR insert, but garbage otherwise. A definite buy at $10, today they cost $16, still may be as good a deal on a handheld mic body as there is. Prices and included items from ZRAMO vary from time to time. (USA)
Re: Where to buy electronics parts in the EU

 

¿ªÔÆÌåÓý

Season Greetings from Sweden,

From where I live rs-online.com, digikey.com, mouser.com, conrad.com and tme.eu works equally well for generic components, free shipping on many orders except from tme and speedy delivery (especially digikey - sometimes astonishingly fast!).? Digikey is often the less expensive choice but not always.
Re: SimpleP48 -- Polarity

 

" the voltage across the cap should increase (greater charge density), which causes the FET to conduct more,¡±

But the + terminal of the capsule capacitor (the diaphragm) is connected to the shell of the electret capsule. Ground. Signal comes off the negative terminal (backplate), driving the gate of the FET negative. Fet conducts less, so drain voltage goes up. Positive air pressure, negative voltage at backplate, signal inverted by FET amplifier.

Electrets behave differently than ¡°true condenser¡± capsules. The electret¡¯s polarizing field is built in, so reversing the capsule connections reverses the polarity of the output. This is true whether the FET is built into the capsule or external.

The ¡°true condenser¡¯s¡± polarizing field comes from the mic¡¯s electronic circuitry, so reversing capsule connections as seen by the capsule reverses both signal polarity and polarizing voltage polarity, and signal polarity at the FET gate does not change. What determines signal polarity is polarity of the bias or polarizing voltage relative to the signal terminal of the capsule.

For examples of electret mics with multiple patterns, see:

and:


If one were to substitute a pair of ¡°true¡± condenser capsules for the electrets, and supply polarizing voltage from the electronics, the circuit won¡¯t work. The easy way to switch signal polarity of a ¡°true¡± condenser capsule is to switch the polarizing supply from + to -. But that¡¯s a different topic.
Re: Where to buy electronics parts in the EU

 

¿ªÔÆÌåÓý

Oh yes, I have used Conrad in the past. No issues.

Also, I sometimes buy from US suppliers and use Addresspal for delivery.? Addresspal is much cheaper than the usual couriers, quick, and handle all customs issues.





-------- Original message --------
From: Jerry Lee Marcel <jerryleemarcel@...>
Date: 24/12/2023 15:14 (GMT+00:00)
Subject: Re: [MicBuilders] Where to buy electronics parts in the EU

On Sun, Dec 24, 2023 at 03:50 PM, dimento454 wrote:
online stores to buy electronic components

RS is a good supplier but does only B2B.
Digikey is not bad but often there are hidden costs.

I would suggest trying Reichelt, W¨¹rth or Conrad.
Re: Where to buy electronics parts in the EU

 

TME electronics is another source. I believe they are based in Poland.
Re: Where to buy electronics parts in the EU

 

Am 24.12.23 um 17:20 schrieb Gerard Lardner via groups.io:
Oh yes, I have used Conrad in the past. No issues.
They've just closed their last remaining shops in Germany and announced
they will do only B2B in the future.

I've boycotted them for the last 20 years. Years ago, they opened some
kind of superstore here in Cologne, kept it open until they had ruined
the dozen good local electronics stores we had before and then closed
their own store again.

Not the kind of company I like to do business with.

Ralf

--
Ralf R. Radermacher - K?ln/Cologne, Germany
Blog :
Audio :
Fotos :

Re: Where to buy electronics parts in the EU

 

¿ªÔÆÌåÓý

And there are some smaller suppliers, mostly in the west of Ireland; but prices can be high for smaller (non-industrial quantities and through-hole components.?
Re: Where to buy electronics parts in the EU

 

¿ªÔÆÌåÓý

Oh yes, I have used Conrad in the past. No issues.

Also, I sometimes buy from UK or US suppliers and use Addresspal for delivery.? Addresspal is much cheaper than the usual couriers, quick, and handle all customs issues. Check out?https://addresspal.anpost.ie/
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