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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

Hello, I've drafted up a DIY design that I think could work to drive an electret capsule like the TSB-2555B through the use of a DC-DC converter (IEB0105S12) to derive a stepped up voltage from the 5V supply rail of a USB soundcard. The generated voltage of the microphone is fed into an amplification circuit from the OPA-Alice circuit. Presented below is the proposed amplification scheme: Similar to the aforementioned OPA-Alice circuit, the amplifier to be used is planned to be the OPA1642. The USB soundcard to be integrated to the design utilizes a CM108 IC with an input range of 2.88 V pk-to-pk and a default input signal gain stage of 20dB (gain of 10). I am relatively new to the design of microphone circuitry and this design is heavily inspired the by videos and instructables from DIY Perkz and DJJules. I would like to ask for advice regarding the design choices made and the validity/viability of the proposed design.

Ever since I built a few pairs of Jules' hydrophones, I have been interested in new ways to make recordings with things other than traditional diaphragm microphones. I have been thinking about building a set of contact mics using Jules' circuit and a flat piezo disk. One of the things I want to record is a passing train. Then I got to thinking...I also having been tinkering with electric guitar builds and I have a few cheap pickups from kit guitars where I replaced them with better ones. Rails are steel. Like guitar strings. What about putting a pickup on each rail. Run them through direct boxes and into my Mixpre and record a passing train?

Hi all - Any recommendations for cheap-ish electret elements that go up to 40kHz? Thanks!