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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

Hi all, I would like to create a little circuit box that merges the signals of two ambient mics (L/R) with a single vocal mic (M) before entering the preamps. So I can record stereo ambient and vocal simultaneously on my sony cassette 2 Track cassette recorder. The recorder has two decent mic preamps without phantom power. Is that possible? How would a circuit like this look like? I was thinking of using two omni primo capsules for ambient and a XLR input for the extra vocal input (potentially condenser +48V). Ideally there would be a single switch or potentiometer with which I can switch from only ambient, to only vocal mic, and some in between settings. Is there someone that could help me out with a circuit sketch? And what would be the easiest way to add phantom power to that device? The whole rig is intended to be used in the field and with batteries. I could install 9V block batteries or also 3,7V Lipo batteries as power supply. Any help is greatly appreciated! Thanks M

So ive built an Ambi-Alice based on the Instructable by Jules and used em272 capsules. I noticed my mistake (that these are omni and not cardiod capsules) and ordered some TSB2590 knockoffs off of ali. They arrived and sound fine but I get a weird electrical buzzing sound wich gets amplified if i touch the capsules, so i suspect it could be a grounding issue. I used 4.7uF Capacitors and 100k ohm resistors for the simple p48 circuit wich worked great with the em272s and should also work fine with the new capsules right? Is there a way to fix this? The instructable doesnt use the cable shielding connected to the microphone capsule, could this help or am i gonna destroy the mics by doing that? Any help would be appreciated :D

Hello, everyone. I am someone who has been receiving a lot of help from this community. Recently, I have been studying microphone output impedance. I noticed that there are various terms commonly used, such as "output impedance" and "symmetrical impedance."First of all, I am confused about the definitions of these terms. Can I assume that the two terms mean the same thing? From what I understand: "Output Impedance" refers to the impedance between Pin 2 and ground on the microphone. "symmetrical Impedance" refers to the impedance between Pin 2 and Pin 3 on the microphone. If that is correct, I would like to know whether the impedance values provided by manufacturers refer to output impedance or symmetrical impedance. Secondly, I have a question about the method for measuring impedance. From what I have studied, among the XLR pins (GND-1, HOT(+)-2, COLD(-)-3): In the case of measuring condenser microphone impedance using voltage drop, should I connect the load RL between Pin 2 and Pin 3 to calculate the impedance? Or should I connect separate loads RL between Pin 2 and ground, and Pin 3 and ground, to calculate the impedance? Which method is correct? Thank you for reading. I hope you all wrap up the year well!

Hi All, Do you know of any designs or indeed PCB modules for active noise cancelling in a microphone? I repeatedly encounter two situations recently where background acoustic noise is a significant problem when needing to use a microphone. Using a dynamic mic helps a bit, but still fails to cull enough noise. It has gotten me curious about whether there's an active noise cancelling solution. A) Commentating on a rowing competition: This involves cycling down a towpath, with a headset mic on, meaning weight and size limitations. Spectators are typically standing alongside the towpath, cheering. Bank party crews use whistles and air horns to signal to the rowers distances. So all of this noise is largely within the speech frequency band and is coming from in front, behind and to one side of the cycle commentator. B) Flying a General Aviation aircraft: To keep aircraft weight down most light aircraft don't have much acoustic dampening between the engine and the cockpit. So the cockpit is rather noisy both acoustically (and electromagnetically). To communicate with each other and air traffic control via the radios, we use headsets with microphones. The headphone side of things is usually passively noise cancelled at minimum, and many people opt for actively noise cancelled headphones. However by the looks of things, the mic side of things is less clever: it's typically a cardioid pressure gradient electret, or a cardioid dynamic. The noise is predominantly coming from the front, with a particular prominence in the lower frequency end of the speech band from the engine. It's not lost on me that most unidirectional mics tend not to be that directional in the lower frequency range. (NB: there are no certification requirements for the mic/headphone side of the comms equipment for the aircraft I fly) It got me wondering: Would some sort of active noise cancelling for the mic be possible, or is a single directional mic transducer plus a speech band-pass filter the best we can hope for? Is there a good speech processing DSP chip which can identify a speech signal, and chase the signal frequencies, filtering off other frequencies? Could we use multiple small transducers and employ beamforming? If so, are there any PCB modules doing this (e.g. from conference room boundary mics) In other words, how would you achieve real-time speech isolation in these noisy environments?

Learning more about building ultrasonic microphones, I posted a while ago about ultrasonic electret mics. I've found the advantages of them for sure, being nice and easy. learning more and more though, I'm looking for something that gets up to 100k, like the oh-so expensive Sanken CO-100k. I've measured up to 40k on the electret mics that i'm using, which is very nice. but I want more. does anyone offer capsules that have that sort of response? If not, what are the other options for achieving this high of a response? Is the only option to build them myself? As a sound designer, I'm looking to capture the largest amount of frequencies possible. Thank you again, you incredibly knowledgeable people! -Soundwich

Hello everybody. I'm going to try for the first time to build a microphone with a PUIaudio AOM-5035 capsule + SimpleP48. The choice of this capsule is due to the fact that I need 135dB SPL of maximum sound pressure. My question is: since the capsule has three pins, is it enough to add a 48k resistance to the drain and maintain the manufacturer's recommendation? I attach the manufacturer's recommended drive circuit. The capacitor, could it be a 10uF 25v DC Aluminum Electrolytic? I thank you in advance for your contribution and wisdom. Gustavo

Hi together I recently purchased a Rode NT1-a from a thrift store with a “No Tone” sticker on it. If I connect it to the audio interface and activate phantom power it doesn't work. Miraculously, after three minutes of warm-up time, the gain meters start and the NT1-a seems to be working perfectly. The sound is crisp and clear. No noise can be heard either. I opened the mic body. The circuit board and the caps look clean. The only thing I have noticed so far is that there is some dirt and dust on the capsule diaphragm. Does anyone have an idea what might be wrong? Should I replace the capsule? Many thanks! Heinz @NaturePattern

Morning all, I’m on the hunt for some piezo tubes and came across this supplier: Search physikinstrumente.co.uk They seem to have a wide range of sizes and thicknesses available and I wondered what the theory is behind the dimensions of the tube for hydrophone purposes. Is bigger and thinner always going to be better? Any insights gratefully received, Jack