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Hi all, I've been using polarised aluminium electrolytic caps in my designs as per the advice of members here and also how they are used in schematics like the Alice, etc. This has been going great, though I'm currently working on a pencil mic and to fit into the tiny space my circuit board (and also the mic body) has gotten very long, so I was hoping I might be able to shrink down some of my largest components — great big capacitors. I have already been following the guidelines for minimum component spacing from PCBWay, and this has helped, smaller component footprints would help further. My understanding is that aluminium electrolytic caps are a great combo of cheap, able to reach large values, and stable in a large range of conditions. I briefly looked into MLCC's, but quickly found multiple sources saying that these are not stable enough to be suitable for precision audio circuits. All of the evidence I've found so far tells me that the polarisation of electrolytic caps is a limitation rather than a useful design trait, but I wanted to double-check with you folks whether there is some secret usefulness to the polarisation when it comes to the subtleties of microphone building. If polarisation is required, that limits my choices. In light of that, is there an alternative kind of cap I could be using in my designs that is more compact, perhaps with the trade-off of being more expensive? I only need a handful and I'm not mass-producing these, so components in the range of dollars instead of cents is not a big deal in this case — I'm much more concerned about making a smaller PCB. The only values for electrolytic caps that I'm using in this design are 47uF and 4.7uF, so even if there is an alternative for the smaller value that will help a little. Cheers, Zander.

Today I stumbled upon an interesting project that might also be of interest to some mic builders. It appears that Stuart recently detected a rare sine wave in the magnetosphere, during one of the strongest geomagnetic storms in the current solar cycle. The following article contains lots of useful information about his DIY methods (IMHO). I dropped it to Heinz_Files.: ...Earth Magnetometer Project... A interesting video on the topic: Timelapse of Aurora Borealis with Sonification of Solar Wind...

I purchased a Rode VXLR+ recently and was very disappointed by the noise introduced by this adapter. I compared a Rode SmartLav+ connected via a TRRS to TRS adapter to the VXLR+ versus a SM58 dynamic mic. With the gains set so that both mics had the same response to a sound source, the SmartLav+ via the VXLR+ had a much higher background hiss, to the point of being unusable. I got a similar noise level when I connected a 2.2k resistor to the VXLR+ instead of the SmartLav+. This SmartLav+ works fine plugged directly into a Zoom H1N. I have read several good reviews of this adapter and a few who have found it very noisy as well. Zach Poff has published the schematics for the VXLR+ here https://www.zachpoff.com/resources/testing-xlr-adapters-with-plug-in-power/ I assume the noise is coming from the zener D1. I measured the capacitance of C1 and it did measure 10uF. I have not tried to measure its esr. I changed C1 to a low esr 100uF tantalum capacitor (KEMET Part Number: T520B107M010ATE070). This has a wider body than the original, so you need to offset it towards the center of the PCB so it does not touch the side of the case. The noise level of my modified VXLR+ is now below the self noise of the SmartLav+. I have also since made some recordings of birds with this adapter connected to a AOM-5024L. Perhaps my VXLR+ was just a bad one due to variability in zener self noise and capacitor esr. However I am surprised how little effort has been made to filter noise from D1. A simple additional RC filter could make a big difference without making any significant difference to the cost. David Walton

Welcome to the annual beg-a-thon for funding our space on Groups.io! The yearly cost is $220 USD. Every year we've gotten more than enough from members to pay that bill... and usually a little surplus. The surplus from last year is $28.73. So a few of you very kind folks kind of jumped the queue and already sent me money... right now we are at a total of $149.39, including last year's surplus. So there's another ~$70 to go. Thanks, -Scott -- ---- Scott Helmke ---- scott@... ---- (734) 604-9340 ---- "I have ceased distinguishing between the religious and the secular, for everything is holy" - Joe Henry

Hey, it's that time of year again! I'm out of town for a couple more days, so I don't have access to my usual pitch and all that stuff. But basically the group costs a couple hundred dollars a year to run, and usually it's paid for by donations. So it's on your radar now... when I get home I'll look up the amount, see if there's any surplus from last year, and all that stuff. As always thanks, not just for the support but for the fantastic content we have on this group. Thanks, -Scott -- ---- Scott Helmke ---- scott@... ---- (734) 604-9340 ---- "I have ceased distinguishing between the religious and the secular, for everything is holy" - Joe Henry

I hope this is OK to ask here as it isn't exclusively a mic question but a general electronic question that might be applicable to some mics. Consider a fet input with a high impedance, that is connected to a exposed bare wire or RCA type plug, because it needs to be unplugged from the source. This could be for a piezo pickup with an input impedance of 5-10M or it could be for a condenser mic with an impedance of 1G Do I need to protect that bare fet gate from ESD it might encounter in the world? here's a schem to illustrate: https://halfshavedyaks.xyz/forumimages/fetbuffersm.png I have naively added diodes but I'm not sure if they will actually lower the input impedance which obv I don't want. The real-life behaviour of diodes at high impedances is beyond my current level of understanding. I'm also not sure if 1N4148 are big enough to offer much protection. Nor am I sure if R1 offers any protection. Could any of the experts here talk me through what would be wrong with the attempts at ESD protection in this schematic?

Two decades ago I was an active DIYer and built a couple binaural heads, some PZMs, and other projects. About the time Panasonic was discontinuing the WMxx (61? See, it's been that long), I ordered a bunch of capsules to play with, I think from JMI, but it might have been a group buy that Bob Cain put together. Now I have a use for a 9mm electret capsule, and I've got this package with some TS-94A capsules, and also some TSB-9445A and TS-52B. What I don't have (at least not on any hard drives I have spinning, or useful results from that once search engine, now ad flyer Google) are spec sheets for those capsules. I remember enough to put together a 9v battery, a ??K resistor, and a DC blocking cap, but I'd like to get the resistor value close on the 1st try. Does anyone have spec sheets for this old Transsound capsules, or a link to them? Thanks much, Mike

Has anyone here tried either of these dynamic mics from AliExpress? Fifine K669D Maono PD100 They look like solid bodies, I'm curious if they come apart easily and how good they would be as donor bodies. https://www.aliexpress.com/item/1005005510482582.html https://www.aliexpress.com/item/1005004887926822.html

Pondering how to choose SimpleP48 resistors, it suddenly occurred to me that we can use the techniques in FETbias.doc so I've updated that in my Files/Ricardo directory. It's so obvious with hindsight that I beg yus guy's pardon for my stupidity. Measuring at 9V is perfect cos we want 5 - 10V Mea culpa, mea culpa, mea maxima culpa.

I’ve been looking around to try to find some sources of material to enable me to learn about how amplifiers work. I’ve only got the most rudimentary electronics knowledge so end up floundering very quickly. I bought The Art of Electronics a while ago and have had a cursory browse through it. I was also recommended this paper by an old work colleague. https://1drv.ms/b/s!Ap5IR9dQ9eMPgfxAOWdiIkU-1cGvcQ "Audio power amplifier design" has also been recommended to me. What do you guys think / recommend to enable learning about these things? It seems that a lot of you are well versed in the ways of coercing electrons

Is there a way to connect a 3 pad electret (ground/source/drain) to the Linkwitz 2 wire solution? Thank you!