Archive for the ‘studio’ Category

when last we left our intrepid crystals

Okay, up front: I have built a working crystal microphone! It wants a fair amount of equalisation added to it, but that’s okay because I can do it in the digital audio workstation. (Normally there’d be some circuitry in the microphone to do that, but in this case there’s not. Reasons.) And, happily, it’s picking up the kind of range you’d expect out of one of these old mics. It may be boosting the midrange pretty hard – harder, I suspect, than traditionally – but it’s picking up a good chunk of the spectrum.

It also really should be used with a pop filter (I didn’t), because it has the biggest damn mic diaphragm you’ve ever seen:


So enjoy some old-school crystal microphone test recordings, made with a mic built from cardboard tubing, wires, piezo cristals, and old styrofoam cups(!), and I’ll tell you how everything I did last time got thrown out before I eventually got this to come together.

It’s 1944 Forever Faux BBC Radio: NO equalisation
Faux BBC Radio: WITH equalisation
Constant Sorrow: NO equalisation
Constant Sorrow: WITH equalisation

Okay, so, right. When last we left our intrepid crystals, I had a nice little circuit in a nice little modular box, so I could test about 90 kinds of resonating bodies without having to solder everything to everything, and maybe I could keep the most interesting ones and use them in different situations.

But it had a lot of noise – I mean, like goofy amounts – and wasn’t boosting signal the way I thought it should be. I just chalked all that up to being in a test harnesses, and all that.


I still don’t understand what was going on. I thought I’d built the circuit wrong, but taking a known good one and putting it into the modular box made it misbehave as well. Removing the plugs and soldering directly didn’t help either – just as much noise, just as little signal.

Eventually I figured out that if I had the circuit in the modular box, it would be full of noise and lacking amplification. But it could be the box, she said, desperately clinging to sanity, that doesn’t make sense! Besides, I’d taken the circuit out of the modular box, and set it nearby, and that didn’t help.

Then for unrelated reasons I moved the circuit further from the box. A lot further – like, up to head level.


Given that behaviour also improved when I shortened the cable leading to the piezo pickup, I suspect there is Something about My Cable Stock, and for now, I’m just going to leave it at that. But really, I don’t know.

That case is now Gone. It can be Someone Else’s Problem Forever.

I had also mentioned in comments a couple of places that I had a Really Cool Idea for a suspension harness to hold up the resonating element, which I’d chosen to be the base of a styrofoam cup, as it tested best overall. I was so pleased with this idea that when it utterly failed I was a whole ‘nother layer of So Very Angry.

Anwyay, the idea: take some nylon mesh, the kind used for pop filters. Stretch it across the resonating body. Adhere it to the styrofoam’s outer ring using – hm, This to That says hot glue. OKAY!

Then take that same foam and nylon assembly, and stretch the outer nylon across the microphone case’s front opening. Hold the nylon in place on the outside of the can with a rubber band. It’s perfect! The nylon is acoustically transparent, so will have no effect on sound, and being so lightweight, it won’t dampen responsiveness! It’s GENIUS!

We’ll cut away that middle mesh as soon as the glue is stable

Another can! This one make of shipping tube and aluminium tape.


Well, okay, it was pretty transparent in terms of frequency blocking, I guess that part was true, but even at nearly slack, the amount of response damping just… okay, when I was testing this, I was still testing it with the EVIL CASE OF EVIL, so that was probably part of it, but the amount of signal reduction just depressed me. SOUND SOUND WHAT IS SOUND NONE FOR YOU.

I don’t have any pictures of that setup, which is again because SO ANGRY. So there y’are.

After that, things started turning around. That’s about when I realised how light the styrofoam disc resonating body was. It’s made of sides of two styro cups, flattened a bit and adhesed together with very permanent double-sided tape and cut into a circle, and weighs practically nothing. It is, in fact, so light, that…

…the wire connecting it to the circuit board could maybe be used to hold it up. As long as we can hold the wire in place, that’s worth a try, right? And I’m taking everything apart anyway, so let’s try it:

Piezo crystal is on back of that foam

Circuits just kind of hanging out the back, lol

Foam pushed into the can. Giant resonating disc in front. Hit it.

And it worked. FINALLY SOMETHING ON THIS PROJECT WORKED it was such a relief – on Friday, with things just exploding everywhere, I was pretty damn crazy because seriously it was one of those escalating-personal-chaos-field days, and physics just took a holiday or something and it took a few days to hammer it back towards reality.

So then it was time to make a more proper kit. First, of course, cut some foam more precisely, so the resonator would stay held firmly in place, making sure you leave enough room for all the circuitry bits.

I used some of the leftover delrin plastic to make a back cap for the microphone can. This let me use a standard XLR connector, which I really wanted to do – wire nuts and twisting may’ve been okay in 1938, but with the amount of RF flying around the Lair (and off me!) I really can’t do that. It has to be shielded, too – more copper tape solved that problem just fine.

I still need to build a proper hanging system, so it can hang the way these are supposed to. It’s not as cool looking as the carbon microphone, I’ll just acknowledge that up front. But it’s nice and compact – relatively speaking – and it works.

Another variant will be to replace the styro with that clear Boeing plastic. When I was running tests, the signal level on that was… not real high. But neither was the signal level for anything else, and in the breakthrough moment when I figured out that somehow the plastic case was A Problem, I was using the clear Boeing resonator. And of all the things I tested, that had the best sound. So I think that’s worth another go, and I do have a spare circuit.

(I think. I think I have a spare circuit. I also have more and larger pictures, like usual, over here on Flickr.)

But even if that works, and if I prefer it, I’ll keep this one. It does have a very old-time-radio sound – newer than the carbon mic, but still… old-time.

Plus, the damn thing functions. After this past weekend, that counts for a lot.

This is part of a collection of posts on building microphones and microphone-related kit, such as mic pre-amps.

confused by background radiation

A really weird thing is happening with the crystal mic. I do NOT understand this.

The same circuit board taken from another box and put in this box is much noisier. Like, 15-20db noiser. Both boxes are metal or metal-lined, and I’ve checked – repeatedly -the metal lining on this one is grounding.

This is true even with no crystal element attached.

Also, any board put in this box is quieter – less signal. This makes even less sense.

I’m so confused.

This is part of a collection of posts on building microphones and microphone-related kit, such as mic pre-amps.

presumably the crystal gems would use this kind of microphone

Apparently, I’m really into old-fashioned microphone technologies at the moment, and really, I’m just fine with that. I’ve had this boundary-microphone idea in my head for a while – I even ordered a bunch of parts to build it – and that idea and crystal microphone technologies go together!

Okay, first, crystal microphones were an actual thing. Popular from the mid-1930s through the early 1950s, they were used on-air and in music recording. They’re still in use in certain applications, much like carbon microphones are, but more widely – if you’ve heard of a “piezo buzzer” or “piezo instrument pickup”, that’s exactly the same technology, only applied to a different goal.

The underlying physics: there are crystals which, when flexed, will produce electricity. The charge is positive or negative, depending upon how the flexing is done. Sound waves are enough to do it, which means bing! Microphone technology! This is Neat. And, yes, I have a sample mp3 below.

Hey, that 60s and 70s Skiffy fascination with crystals had to come from somewhere.
(Speak clearly into the pinky ring, Zed.)

It works the other direction, too – current one way will flex the crystal one way, current the other way will flex it back. You can make speakers out of this, and that’s been done. This is also how piezo buzzers work – cycling AC power through a piezo-effect crystal.

I’ve built a couple of piezo-based pickups before, using the Cortado kits, so that seemed like a good place to start. I’m not bothering with a second board-construction write-up; the first one is here, if you’re curious.

But building the carbon microphone driver circuit as an external box made me realise that I should build this mic using an external driver circuit as well, so I can experiment without taking apart the box every time. So I used the housing from a dead laptop power supply I’d recycled a while ago.

The best part was that the AC mains connector slot was almost exactly the right size to hold the XLR connector. I just had to file away a bit at the narrowest points. And, of course, I had to line the whole thing in conductive metal tape, for RF shielding, and ground it.

The Now-Modular Cortado. Piezo lead on the right, XLR to board on the left.

Looks almost professional!

TRS: Tip is outer disc, ring is crystal disc, sleeve is shield ground

Standard balanced XLR mic-level output

This lets me plug in anything crystal or crystal-signal-level-like and use this amplifier on it, just as with the carbon microphone, but for carbon-technology elements. In this case, I’ll be plugging in a piezo disc. But since that’s just the crystal, the real question becomes, what resonates it? What vibrates in the presense of the sound, causing the crystal to flex?

My initial idea for materials involved a lightweight, rigid plastic. I’d also thought briefly about metal, but decided that would be too heavy, and I was right about that. The bad news is, that also turned out to be true for the plastic – it takes too much energy to make it move, so it doesn’t move very much just from soundwaves, and the signal levels were really low.

This is the best I got, using the lightest of the “heavy” plastics. That recording was made talking into a small, clear rigid plastic sheet – I think it’s some sort of acrylic, but I don’t know. It came from Boeing! But does not fly.

I love distant-shortwave-sound of this recording, but that hiss isn’t an added effect – it’s amplifier noise from boosting the signal high enough to hear properly. So, obviously, that won’t work as planned – unless I need exactly this effect, of course.

Still, I’m thinking I could put it in front of a guitar amp or something else VERY LOUD. It’s modular, so there’s no huge reason not to keep it, and I have like 50 of these piezo discs. It also works as a gigantic contact microphone/pickup.

So I started working my way down material weights until I found something too lightweight.


The thin and tinny base of a styrofoam cup


More and larger pictures on Flickr, as usual.

The lighter I got, the more response to sound I got, and the more signal – to a point, of course.

It turns out that the best weight is way closer to the styrofoam cup bottom than to any of the plastics I’d hoped would work out. A pair of thin foam dinner plates did actually rather well – I’d thought it was just one thicker plate, but no, it was two plates! – and I’ll try that again with a better (by which I mean actually shielded) test harness pickup, and plates that don’t have divided food sections.

And also, that styrofoam plate with the last 15mm or so of the “cup” still attached worked pretty darned well, without the echoy effect of a “cup” microphone. Some people want that; I am not one of those people. (But again, modular! And I have 50 of these piezo discs, I could make one anyway.)

This gets closer to the original construction materials used in the original crystal microphones, so really, I have no business being surprised here. I was just hoping that with improvements in crystal technologies that a heavier plate would work. But it’s just not generating enough signal output.

And that’s really kind of putting the kibosh on my whole boundary-microphone idea – at least, using this technology. Nothing strong enough to deal with the requirements of a boundary microphone – they’re quite large – is going to react enough to sound to give a decent amount of signal. Unless there’s some unexpectedly light and strong foam.

At least, not with these discs.

Maybe NASA has something I could, you know, appropriate. And I wonder if I can find that crystal material in, oh, one big giant sheet, and stick that to something strong enough. It has to come from somewhere

This is part of a collection of posts on building microphones and microphone-related kit, such as mic pre-amps.

Collection: Microphone Buildout Projects

Building microphones is fun and seems to be of interest to readers, so here’s a collection post for posts about that! These posts discuss building both microphones, and, when applicable, their matching microphone driver circuits and/or pre-amplifiers.

Building a Carbon Microphone:

Related posts:

Building a Crystal Microphone:

Building a Ribbon Microphone:

Building a Large-Diaphragm Condenser Micrphone:

Other microphone and preamp customisation/modification posts:

not just a display piece

Laying down timing tracks for the new album, finally. I did four and a half tracks yesterday – this is a quick process. None of these recordings will make it onto the final, but it’s a helpful step.

For the moment, the new microphone is living as a display piece in the corner of the room, on the shelf with all the other microphones. Every time I see it, I consider more places I might actually use it on this album. XD

This whole thing got started by looking up how to fake bullhorn vocals, like I needed for the new single, Pee Police (on Bandcamp, YouTube, and Soundcloud). Universally, people said the best way to do it was use a real bullhorn. I mean yes, I’d wanted to build a carbon microphone for a long time. But in terms of actually doing it, this was the prompt.

If you want a specific sound made by a specific thing, the best way to do it is have that thing. $19 in parts later, I have it!

“Starship on Fire” is so far the most likely track to get some carbon mic vocals in the mix. Since it’s told – sung? – from two different viewpoints at once (past character, present character implied), one of those viewpoints having this kind of effect makes storytelling sense. I will at very least try it, and see how it sounds.

I’m going to use the Korra On the Air icon for all the LJ and Dreamwidth crossposts that mention this microphone forever, aren’t I? Yes. Yes, I am.

It’s a long weekend for a lot of people reading this, so – yay! Go have some fun.

a mic of constant sorrow

I’ve been trying to build a carbon microphone. Why? Well, partly, because I can, and partly, because if you want that “telephone” sort of sound, the best way to do it is to use a telephone element rather than fake it later (see also: BULLHORN), and partly because I want to be able to sing into a can, like them fellers at the radio station.

A Microphone of Constant Sorrow

And this should be – electrically, at least – very simple. Small power supply – battery is fine – resistor or two, capacitor. Done. Very simple circuit.

But it isn’t working, and I have absolutely no idea why, and I’m highly frustrated. I’m going to try a higher-voltage circuit, which I’ve been avoiding for no good reason other than it shouldn’t help, but I’m starting to think the carbon element I got new-old-stock off eBay isn’t up to snuff.

Anybody else built one of these monsters before? I have actually managed to get extremely-low-volume recordings out of it a couple of times – far too low level to be useful, I’m afraid – so I don’t think the element is actually dead. But honestly, I have no idea.


A WAV of Constant Sorrow

t0000000bs: let’s try that preamp again with russian aid

Yesterday it was Polish jokes about Soviet technology; today it’s trying a Russian-made TUNG-SOL tube in that ART TUBE MP mic preamp I played with last week. I got advice from Ben Deschamps that I should, because the ART preamp ships with whatever was cheapest that day, and swapping tubes around can make a big difference.

And, hey, I think in this case it rather does. I’d apparently had a best-case low-bidder tube before, so bringing in the Russian didn’t make a big difference in noise level. But the amp’s tonal differences are certainly highlighted.

I should note: I also realised I could bypass the mic preamp stage in my TASCAM completely by going to line-level inputs, as opposed to leaving it in the mic input port at zero gain, like last time. The effect should be similar, but may not be. Regardless of which change mattered the more, I really think you can tell a difference between the preamps now, even in mp3.

The Russian-made tube gives the ART TUBE MP a lot more of what I think of as a “guitar amp” sound. That’s 100% unsurprising, now that I’m typing it out, but it’s still interesting to hear it.

The way that this preamp “likes” mid-bass is emphasised more, I think, as is its noted disinterest in the finer points of higher harmonics. That part of the sound reminds me of the AKG microphones I have, but with more interesting sonic effects down in lower frequencies. I suspect it would get on well with cello, as the AKG200s do.

I don’t know that I’d call the ART “warmer” at the high end – I might call it “less precise” – but it’s certainly a difference regardless. I should try this with the AKGs, later, to see if their similar areas of interest lever each other up a notch, or clash in some unfortunate way. Pleasantly, I have pairs of those, too.

For the recordings linked below, I’m switching between the two basically identical M-Audio NOVA large-can condenser microphones set up side by side and played into simultaneously. The levels are as close as I could reasonably get; it was a bit harder this time, as there were audible differences, and I’m using a bit of light compression as would be used in real life.

Unlike before, since the difference between the two preamps is more obvious, I’m also including a 50/50 mix between the two inputs during one of the repeats in each of these. That produced some interesting qualities, I think, on the octave mandolin.

In both recordings, ART MP tube pre-amp starts; TASCAM follows. Tell me what you hear on your speakers!

Whaddya think, sirs?

wifi progress, and a new show

Short notice show! I’m playing with Leannan Sidhe at Shoreline Community College’s Black Box Theatre on November 6th. It’s part of the Express Yourself Showcase. I don’t know what the rules are for audience admission – as in, whether it’s students and faculty ID required – but if you’re around, come watch the fun! There are lots of groups performing.

We’ve made some progress on the Lair’s wifi situation, particularly on the lowest level. We’ve gone from really quite a mess to something a lot more reasonable. To wit, enjoy some signal-to-noise ratio maps:

Minionland and Chudville had Really Bad Wifi

Minionland and Chudville have Much Better Wifi

Colder colours are noisier, blue is pretty bad, unevenness is generally not good. I’m showing signal-to-noise maps rather than raw-signal-strength maps because as long as you have enough signal to use, S/N ratios are much more important than raw signal power. A full-strength signal that’s 30% garbage is useless; a weak but audible signal that’s clean is just fine. So.

There’s less yellow super-hotspot area now, but you’re not going to get much throughput improvement between those strong green levels and the yellow. The evenness of field should help with reliability, of course – that’s lots and lots of yellowish green, which is pretty solid.

And most of all: no more blue. Blue in this software means problematic levels of noise. I was seeing S/N headroom numbers as low as 20db, and regularly in the low 20s; that’s not disastrous, but it’s not good. Now we’re reliably in the 40db range, which is a huge improvement. dB is logarithmic, so that’s not twice as much headroom, it’s 100 times the headroom. It’s a lot.

To get here, we’ve done a few things. One, we got seriously started on the RF noise suppression in the wiring through liberal use of filter units and ferrites. There’s still lots to do, but it’s a start.

Two, we moved the primary lower hub so that it’s as close to above the downstairs repeater as I could get without tearing into walls. (The location indicators on the display are wrong; it’s the software’s best guess, and it’s inaccurate sometimes.)

Three, I built a reflector for that primary hub to spread the signal around better on the ground level, the non-CHUD half of which is shown above. (The CHUD half is a secret.)

Also, we had to repurpose a functionally-useless AirPlay receiver as a second repeater, one level up. That repeater is not shown. It’s so that the main level would have somewhat reasonable coverage from the lower network, which is useful for people going up and down stairs.

So, yeah, there’s that update. It’ll be a couple of days before the next set of line filters arrive – I burned through most of through my useful stock – but that will hopefully help with the noise a bit more.

Then I’m going to poke some at the upper network – officially the “west” network, though both “up” and “west” are true – to see if I can get some better south-end coverage out of it. It’s unlikely, but I’ll try. Mostly, I’m happy not to have done it any measurable harm by adding yet another transmitter to the lower network.

Will this solve all our problems? I doubt it. I’ve already found that we shouldn’t be using our upstream provider’s DNS servers. Our servers don’t use it, why should our workstations? So I’ve gone back to using our own, and that’s already helped. But the big job, I suspect, is getting IPv4/IPv6 concurrency sorted. We’re running some IPv6 now, on workstations, and I’m pretty sure some of the stacks are… not entirely ready. And I’m not sure what to do about that.

So much overhead in running a lair, I tell you.

If you’re looking for the Grammy Awards Long List nominees, thank you for listening, and for your consideration.

accidental discoveries

I have this big tall sound baffle I call “the monolith.” It was the first one I made. I play into it, and have people play into it, to minimise bounce when recording.

After Bone Walker was recorded, I moved it back towards the wall a bit to free up more space. Around then, I also noticed the monitor speakers sounded a little weird, a little… hollow? It was hard to describe. Failing to add two and two, I wondered if my monitor amp needed more work or something, but put it aside to think about later.

A couple of days ago I helped somebody with a sound engineering homework assignment on standing waves. Which made me think about this.

Today I finally did some math and HEY putting the monolith were I had originally put it, just because it seemed like a good place? Totally fixed a room mode problem*.

Let’s put that RIGHT BACK WHERE WE HAD IT then, shall we? And never move it again. Perhaps I will nail it down, as a reminder.

*: Two near-double nodes! One pair at 203 and 207hz (not actually so bad), another pair at 274 and 276hz (fairly bad). Moving the baffle back to the old location disrupts both.

resetting the art

Every so often I need to cut through clutter and reset things. My clutter tolerance threshold is actually pretty damn low – most people wouldn’t’ve called my studio cluttered, but it hit that NOPE! point for me and I had to reset it.

I know a lot of people thrive in clutter, particularly creative people. That’s never worked for me. I wish it did, I’d spend less time resetting studio spaces.

On the plus side, it was a good time to change around art. I rotate pictures and such in and out so I don’t get too tired of them. Korra and Toph survived this round, and even got frames, and the Utena art I found at ECCC finally made it onto the wall. Plus I built a little shrine to our favourite Russian Jaeger pilots. 😀

Bigger pictures at Flickr, like usual. Mostly useful for the panoramas, of course.

the usual shot

the far side shot

the shrine, in sepia, because the colour came out weird

underlighting makes everything into art deco

Plus there were actually a couple of things that needed repair, like one of the lamps turned out to have some bad insulation (if “missing” counts as “bad,” which I think is true in this case) so I fixed that and its stuck switch.

And those horizontal lines on the sound baffles? Those are part of the new wall anchoring system. I had a baffle come down while trying to put a speaker away, and that sucks, so I fixed it. Plus, that let me put like three support legs into the closet, opening up more space and getting rid of distracting visual noise. Here’s an comparison to the previous reset, with the above panorama cropped to match.


It’s not a big difference, but people other than me notice it when they walk in, so it’s enough for that. Other than the art, it’s mostly corners and shelves, really. And the closets. Those got a good straightening out. Really, if anything actually needed it? It was the closets.

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