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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. :) |
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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?.... |
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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. |
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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.
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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)
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Re: Where to buy electronics parts in the EU
¿ªÔÆÌåÓýSeason 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. |
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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. |
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Re: Where to buy electronics parts in the EU
¿ªÔÆÌåÓýOh 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 online stores to buy electronic components RS is a good supplier but does only B2B. I would suggest trying Reichelt, W¨¹rth or Conrad. |
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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 : |
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Re: Where to buy electronics parts in the EU
¿ªÔÆÌåÓýAnd 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.? |
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Re: Where to buy electronics parts in the EU
¿ªÔÆÌåÓýOh 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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Re: Where to buy electronics parts in the EU
¿ªÔÆÌåÓýHi D. , I'm in Bray, near Dublin. I use Radionics (Irish division or outlet of RS Components) CPC Farnell (.ie website, prices in euro) Mouser (.ie website, prices in euro) Digi-Key (.ie website, prices in euro) Or Aliexpress, if you are not in a hurry and willing to trade low cost for occasional poor quality? |
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Re: Where to buy electronics parts in the EU
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Show quoted text
On Dec 24, 2023, at 09:06, Adrian Hicks <mail@...> wrote:
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Re: Where to buy electronics parts in the EU
Hello Cork! I'm not so sure about capsules, but Farnell operate all over the EU so they should sort you out in the south. Have you spoken to Nick at micbooster? They'll ship and I'm not sure what the threshold is for getting hammered since that god-awful act of suicide was commited over here. If it helps, I could post stuff in order to try to alleviate charges.? On Sun, Dec 24, 2023, 14:50 dimento454 <damiandrohan@...> wrote: Greetings from Cork, and happy xmas to all. I'm a complete noob and just getting started with some very basic (very very basic) builds. Can any members recommend online stores to buy electronic components - wire, jacks, solder, resistors, boards, capsules etc in the EU? |
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Where to buy electronics parts in the EU
dimento454
Greetings from Cork, and happy xmas to all. I'm a complete noob and just getting started with some very basic (very very basic) builds. Can any members recommend online stores to buy electronic components - wire, jacks, solder, resistors, boards, capsules etc in the EU?
I used to buy various bits from the UK, pre-brexit, but customs now makes it v expensive. thanks so much D |
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Re: SimpleP48 -- Polarity
Slightly off topic, but I discovered an interesting observation on this polarity issue, with my RF bias mic experiments...
I built an LDC mic based on my notes here: https://www.amx.jp137.com? and noticed that the polarity was inverted from my iss.4 Rode NT1, which I used as a reference mic. So I reversed the connections to the capsule to correct the problem.? Except that it didn't .... it made no difference at all ?? It took me a little while to realise that the polarity of this type of mic (which uses the varying imbalance of an RF bridge to amplitude modulate an RF ocsillator ) is dependant on the capacitive value of the capsule. The polarity of the demodulated signal depends on whether the resting capsule capacitive value is bigger or smaller than the 'bridge balance' capactior. Not on the polarity of the capsule connections. If the values of the capsule and the bridge balance capactor are identical - or almost identical - then that introduces a very unusual situation. Application of an audio stimulus? to the capsule will cause the bridge to become unbalanced both sides of the centre balanced 'null' point, and theoutput signal will repeatedly change polarity. Which sounds very strange ! As I say, not exactly 100% pertaining to this thread, but I found it an interesting phenomenon on mic polarity.... |
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Re: SimpleP48 -- Polarity
¿ªÔÆÌåÓý?Something about capacitors and electrets. As i see it. For a normal capacitor, 2 plates with an insulator in between, the physical law says Charge is the product of capacitance times voltage. Thus as the plates move towards each other, capacitance is growing, so the voltage must go downwards. There must be a relation between both plates, voltagewise spoken.That is for a normal capacitor.? The voltage is externally supplied. But in an electrets, the charge is trapped in one of the plates and does not relate to an external voltage source. Thus there is no relation with a second plate.So this law Q=C.V does not work here. Here it is that the voltage wil rise when the plates move towards each other. Just the opposite of a standard capacitor. The charge in the electret just repels the electrons in the opposite plate, so the voltage difference is going up. This is how i can explain it for myself. Maybe i am wrong, in that case correct me. ennjava schreef op 2023-12-24 05:16:
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