収束ゾーンでのライフ: Life in the Convergence Zone

cartridge computing fucking rules

not sure why i said it but i did

 

i decided upon a 'testbed' cartridge instead of 'utilities' because lol what utilities are tiny, but i actually do have a use for a testbed OS cartridge to test newer versions of ubuntu against studio software, particularly new LTS releases, and also 64 bit, because yeah I'm on 32-bit still because of concerns about plugins. but with a separate cartridge (hard drive and booting system) then i can try them without fear.

THIS ACTUALLY SOLVES A PROBLEM

and i hate that

it's so stupid

(if you're just catching up, i'm using an external eSata harness to have a cartridge-slot-like multi-boot system with different SSD hard drives, which, I realised, are basically cartridges like from the old Sega Genesis and before. so i'm running with it because that's the kind of shit i do.)

(the extra storage carts are for power-users with multi-cartridge-slot systems OBVIOUSLY)

I’ve updated the Kitting Out Cheap guide to building your home recording environment on a low budget. New additions include short commentary on kit microphones, updated interface information, and pointing out that hey, guess what – USB chipsets matter!

So, hiya, Home Recording panel attendees – here y’go!

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Lots of artists (including a few I follow) livestream their drawing sometimes, usually showing their desktops so you can see what they’re working on. A fair number of them do this on Picarto, which is pretty visual arts focused, but says it’s for creators in general.

So I decided hey, maybe music? And they even have a category for it. Yay! And I’ve set up an account here on Picarto, and will stream sometimes, probably announcing on Tumblr and Facebook on the band page.

I’ve only tested it once and it was a little weird but I think it worked most of the time? The wifi in the part of the studio where I have to put the laptop is a little wonky tho’, and it cut out at least once. If people come by I’ll work on fixing that.

It’ll mostly be rehearsals/practice but might occasionally be me mixing something or writing something. I dunno! I’ll probably turn it on later today, I completely upended my planned VCON set and I’ll want to try that out this afternoon. And I’ll check the chat window every so often, too.

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hey guess what

hydrogen – a linux-based drum machine – has decided that its 151 beats per minute should be much faster than ardour’s 151 beats per minute.

i gotta tell you, this is turning into a “why do i even try” week. really is.

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After we got back, I discovered that my digital audio workstation had decided to Not anymore. No idea why; it was fine when I turned it off, it was Not At All Fine when I turned it back on.

I blame Bond, James Bond, somehow. Or maybe that turncoat Q. He used to be a supervillain scientist, you know. That bastard.

Anyway, since Ubuntu 12.04 LTS was going to fall out of support in the spring anyway, and since the problem appeared to be some sort of USB driver issue with the new sound interface, I decided I’d upgrade. That went… very badly. (See also, see also, see also, see also, there’s even more on my personal Facebook account, and none of this even covers the first half.)

But I did eventually get it working, and! I found a good use for an under-desk add-on keyboard tray. Look! It’s a LazyRack!

Hello!

Are you still there?

Targeting acquired!

I can do this because unlike my old interface, it’s meant to rack-mount, so almost everything is front-facing. Reclaimed desk space, and pushed back, all the cable ends are still out of the way! It’s great.

Also, I love these mic preamps oh my gods they are so much better. This probably won’t mean much to you listening on laptop speakers, but here’s a quick zouk sample straight into the mics I recorded last night, once I had things up and running. No processing at all, as there shouldn’t be… it’s… it’s just that these preamps (and same mics I’ve had before!) are picking up all these subtleties in the low-end that the TASCAM buried, and I’d have to dig back out with EQ and stuff. This is an absolutely raw recording and it’s all just there already.

It’s kind of like I didn’t just get new mic preamps, I got new microphones too thrown in.

I’ve written many times that you can do a lot on the cheap, and I think I’ve proven that, but I’ve also always said you’re trading time and knowledge (work) for money. I finally decided to run that trade the other way, and still ended up with a boatload of work thanks to Ubuntu. But for the improvements I’m hearing so far, in the studio? I’ll take it.

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I’ve been playing with that ‘added pressure adds bass response’ idea, for use with these piezo pickups. I made a little wooden chamber that would let me add light pressure, as with the bridge pickup design. It would be held down with a clamp for testing, but would isolate that pressure from the piezo itself.

Anyway, I made a bunch of recordings, two for control, and eight with a range of pressure in the chamber. The controls were made with the pickup taped to the front of my zouk with double-sided tape (standard attachment), and with the pickup directly clamped to the front (also a standard attachment) and come first and second in the recording. The other eight were with the pickup in the test chamber, with increasing amounts of pressure on the crystal, applied by inserting paper as seen here:

With thin cardboard and two sheets of paper

Note again that the clamp is not adding pressure to the disc in any way.

Audio samples in a single mp3, here. There is some extra noise in these recordings; I was trying the modular approach again and that’s the result. I think the TRS connectors are inherently noisy. But that’s a separate matter.

I also ran spectrographic analysis on each recording, and combined those into a single animated gif that cycles through the recordings in order. Here’s the key for both. The gif is repeating, so each frame is labelled in the upper left.

 1: taped to top
 2: clamped directly to top
 3: in chamber, no paper
 4: in chamber, thin cardboard (0.46mm)
 5: in chamber, cb+1 sheet  (+0.11mm)
 6: in chamber, cb+2 sheets (+0.21mm)
 7: in chamber, cb+3 sheets (+0.31mm)
 8: in chamber, cb+4 sheets (+0.42mm)
 9: in chamber, cb+5 sheets (+0.52mm)
10: in chamber, cb+6 sheets (+0.63mm)

You’ll note in both the graphs and the audio that bringing in the chamber at all, even with no additional crystal pressure, caused a big drop in high-end oversensitivity, and boosted the low-end. That was interesting; I have suspected for a while that the crystal side of the disc would actually be better as a source-facing element, but there are physical issues to doing that, since the wires have to attach on that side.

Adding pressure continued to boost low-end response through test 7, without inhibiting high-end response. After that, I think additional pressure began to overcome the benefits, and you see a return to a more midrange-heavy sound – though in all cases, I think it’s better than either traditional mount.

This is consistent with tests made in the bridge pickup from last week, and reminds me of a diagramme I saw of a period crystal microphone that implied the crystals themselves would be set up forward-facing.

Anyway, data! And lots of it, for lots of your crystal/piezo experimental needs.

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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:

70mm. YES 70mm I HAVE BUILT A LARGE-DIAPHRAGM CRYSTAL MICROPHONE.

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.

WRONG.

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.

And suddenly everything started working. NEAR THE BOX BAD. FAR FROM THE BOX GOOD. I AM NOT EVEN MAKING THIS UP. I DO NOT KNOW HOW A PLASTIC BOX LINED WITH METAL CAN DO THIS. THIS IS PUREST STUPID ACTION AT A DISTANCE AND I DON’T KNOW WHY.

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.

ABSOLUTELY NONE OF THAT TURNED OUT TO BE TRUE! NONE OF IT!

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.
 
 

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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 HEAVY HEAVY DELRIN SOUND

The thin and tinny base of a styrofoam cup

FAILURES, ALL OF YOU! GET OUT OF MY SIGHT!

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…
 
 

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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.

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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!

• Irish Bouzouki (mp3) – “Supervillain For I Love You (intro only)”
• Octave Mandolin (mp3) – “Thirteen” (a few chosen chordal excerpts)

Whaddya think, sirs?

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