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Hello everyone, I was thinking how cool it would be to record a thunderstorm with a pair of earthworks M50 measurement mics seeing as their frequency response goes way down into subsonic territory. Then I looked at the price tag. Yeah I won't be taking a pair of those things out into the rain any time soon. Does anyone know what top secret Roswell technology Earthworks is using here? Do they manufacture their own capsules or is there an omni capsule out there that is equivalent? I've also thought about the old speaker-wired-as-a-microphone, sub kick idea, but I don't have any way to measure the frequency response of a speaker/microphone. At least not in any practicable way.

Hi, I've been a long -time lurker. I thought I would post up something I'm working on. I've been interested in getting a small, inexpensive Blumlein pair together for recording piano and thought I would try and see if the SimpleP48 works with two electret capsules, out of phase, on one xlr, with two sets of symmetrical capacitors and resistors. It works! I'm using PUI AUM-4537L-HD-R cardioids with 4.7uF caps and 87KOhms resistors. I'm going to try it out with PUI AUM 5241L next, which should be more suitable in terms of coping with the signal from a piano. Richard

I think the name Alice (in microphones) was created by Scott Helmke. If I remember correctly, it was based on 16mm capsule and a FET circuit. Now I see "Alice" all over in the mic DIY communities. Homero Leal calls his "Pimped Alice". Jules Ryckebusch calls his "OPA based Alice". What defines a microphone an Alice?

Hello all, I suspect that the topic of choosing the right resistor values for biasing FETs might be done to death by people as inexperienced as me, but I've searched through the messages and haven't really found anything that answers my questions. I'm trying to make some little cardioid lavaliers using AUM-5241L-HD capsules, which should be appropriate for the simple p48 circuit having an internal FET. I understand that I have to wire the sourse and ground terminals together, but I can't for the life of me figure out the calculations for the resistor values chosen in these circuits. I can use ohm's law to figure out how to bring the voltage from the power supply into the acceptable range, but when I look at the suggested resistor values for circuits for other capsules that's not what the resistor is doing. The typical application circuit on the datasheet (below) shows the same two component setup but with a 3V supply voltage, using a 3.3k resistor. Could I just insert a resistor on the drain to bring the supply voltage down to 3V and leave the rest of the circuit the same? If not, could I replace the biasing resistor with one that can bring the voltage into an acceptable range in series with a pot and find the appropriate value by tinkering? I apologise if I'm way off base, my electronics knowledge is still very limited. Thank you all!

Ricardo addresses this in his /g/MicBuilders/files/Ricardo/SimpleP48/simpleP48.pdf Basically you want the resistor to give between 5 V – 10 V across the capsule. But check that the voltage is not too high for the Vds limit of the FET in the capsule; some, like the NEC 2sk4027 FET used in some Primo capsules do not like that.

Hello all, I thought I'd share my diy wind screens. They cost probably less than 50c each to make, are suitable for beginners to felting and do a fantastic job. For the basic shape I wet felted them - basically wetting the wool with very soapy water, shaping them around the mold (a housing for a sound sleuther mic i made covered in in foil), and agitating it until it roughly felted together. Let dry, rinse soap off and let dry again. Then I took it off the mold, used a felting needle to tidy it up and fill in the thinner patches. For the dead cat style screens I loosely felted long pieces of felting wool in piece by piece until it looked like a troll doll. Overall less than two hours work each. They don't shed much at all either. If you are frugal and hate plastics like me it's a very feasible option.

I’m new to the group and impressed by the knowledge and experience here in the group! I have some questions about Primo EM23: I asked Primo about phantom 48V, and got two ‘answers’: and which of the two suggested circuits is preferred? i.e. one or two capacitors? Then about the FET 2SK118 O1 - this one is no longer available, and the replacement, suggested by Primo, is only sold in quantities of 2,500 from Mouser: any suggestions of alternative FET or where the 2N5457 can be bought by piece? In general, should the electronics be close to the mic capsule or close to the recorder, i.e. inside the XLR, when (5 to) 10 meters in between? I do mainly nature sound recordings … Cheers! /G?ran G?ran Birgersson G?teborg, Sweden

Hi everyone, does anyone know if the Ambi-Alice (GoPro mount version) will fit inside the Rycote "Baby Ball Gag" windshield? They make them to fit 20,21,22,and 25mm mic bodies. I think the GoPro mount diameter is 25mm? I can measure to make sure before I buy, but also want to make sure the basket will fit inside the windshield.

I got a chance to play with these and they are really nice. THis one is Cardiod https://www.jlielectronics.com/microphone-capsules/jli-160a11uc680/ And this one Figure 8 https://www.jlielectronics.com/microphone-capsules/jli-1660nb-38/ I wired the Cardioid one as a "two wire" by connecting the Source to Ground and using the Drain lead as my connection point for PIP power. I'm guessing they both have the same FET as the TSB2590 as they work well with a 100K Ohm resistor in the Simple P48 configuration. I put two Cardioids back to back, one facing front and one back in a quickly 3D printed holder with the Figure 8 at a 90 degree angle to both. That makes a three capsule Double MS setup. I plan on testing this and getting some samples in the near future. They sound really good. Two of the Figure 8's will make a great Blumlien pair that can run into a small PIP recorder. Jules -- Best Regards, Jules Ryckebusch 214 399 0931 Linkedin

I Just had a really cool adventure recording Humpbacks with my hydrophones. See this: https://youtu.be/XrURPtL9zuk One challenge was the failure of two of them post build. I also had a couple board failures after initial testing of the boards prior to attaching the Piezo cylinders. There were two modes of failure. Complete failure of the Opamp causing a higher than normal current draw. Second, it still worked but with a lot of noise. The light bulb went off as I realised that I was directly connecting the cylinder to the Piezo element. I connected my Oscope to the cylinder and tapped on it. I could easily generate 15-20 volt spikes that were visible on the scope. Reviewing the literature, I realized I wasn't including any input protection. Yes there are internal diodes for this in the opamp. I suspect they are fine for "normal use". I am updating the circuit as seen below: This includes a series resistor and two diodes to shunt anything to ground and the supply pins. Conveniently there is a .1uF cap across the supply rails of the opamp that will act as a low Z source for this too. I have my first boards back from PCBWay and will commence testing shortly. Love any advice or feedback here. -- Best Regards, Jules Ryckebusch 214 399 0931 Linkedin

Hello, is there any way to reduce the sensitivity of an electret microphone capsule with a built-in fet transistor? Something like a -10dB or -20dB pad? Thank you. M.

Hello, A while back I purchased a used MTG MV203 measurement mic to use as comparison/testing for any of my future projects. After researching the MTG documentation I built a rack-mounted power supply/preamp to go with the mic. Everything was working fine (PSU functioned nicely & super clean/healthy output from the mic). I moved the PSU into a new enclosure to make things more portable and started having issues with the mic. Sometimes I would get no output, sometimes very distorted, sometimes functioning perfectly. After thoroughly troubleshooting my PSU I found no issues with it at all, which led me down the harrowing road of cracking the mic body open and prodding around with my DMM. Here are pictures of the internals and my best shot at the schematic. Output was disconnected to verify the cable was not causing issues. Had to replace a 6k8 resistor that took flight when I was desoldering the adjacent mystery component. I used the component codes, DMM, and educated guesses to determine most of the components and I plan on measuring the unlabeled caps. I'm fairly confident the High Z section under the resin is two 10G resistors in series and a 0.2 pF cap (input impedance is specified at 20G and 0.2 pF). However, I am not sure what the black mystery components are. Intuition tells me they are resistors, but they must be on the order of >>10M because my DMM cannot read them. I will have to carefully remove them and employ something like this method to measure them on a separate board. Luckily I had also taken a look inside while it was working. I know from my first measurements that, when functioning, the output sits at around 65V DC offset. It now sits around 40V DC (sometimes as low as 24V) and I measure no signal regardless of sound source. Prime suspect is the 1uF tantalum cap as I understand they are prone to damage and considered somewhat unreliable. The dual diodes, MOSFET body diodes (not sure I understand why they are used here), and Both BJTs measure ok with the DMM diode mode. I'm posting this here mostly for general interest, but if anyone has suggestions on troubleshooting the circuit I would greatly appreciate any insight.

Hello, long time lurker here. Thanks for all valuable info in this group. I have an idea to build KM84 circuit with Primo EM200 capsule (theres inernal FET in this capsule). So I sketched basic schematic. I want to ask you if theres something to change or if theres mistake somewhere in schematic. I like the idea of transformer based electret mic, hope it is not totaly nonsens. Best regards Milan