Archive for the ‘diy’ Category

wow it’s been a while since I posted here

Hiya!

Wow, it’s been a while since I’ve posted here, hasn’t it? Well, it’s been that kind of year. I warned everyone that the band blog would get a lot more political, but instead, I haven’t even had time to write political posts. Take political actions, yes. (And also, write a lot of short fiction about assassins. One takes one’s stress relief where one finds it.)

But posts? No. And this isn’t one, either. This is about music stuff!

When I was Festival Mémoire et Racines in Quebec this year, I picked up a cute little noisemaker. It reminds me a little of a kokiriko, but much simpler and smaller, and played very differently. But it was radically underengineered, and the two small dowels used as spacers between clackers were absolutely not going to last – one even broke before I could get it back home.

Which is where attoparsec comes in. Matthew said he could totally make replacements out of brass for me, and that he’d actually kind of enjoy doing such a simple project to unreasonably unnecessary degrees of precision.

To wit:

Looks great, doesn’t it? The metal bits make it look so much more like an actual non-toy effects toy, rather than the Can$10 bit of fluff it is.

So… yeah! Not something I made or even fixed but something which someone fixed for me. Yay! Thanks. ^_^

hey linux networking peeps

I’m finally getting back to working on a new gateway/router server and I’m basically setting up this old-school sort of DMZ, with the rest of our servers hanging off one card, and our internal LAN/DHCP/NAT side hanging off the other. (Using ISC, which Debian seems to like.) And all of that seems to be right from the new server’s perspective, which is yay!

Except there’s no packet forwarding from the DHCP side even though it’s enabled and I’m sure I enabled it and yes the kernel thinks its enabled but it isn’t happening.

Any ideas where to start?

show this thursday!

I’m playing with Leannan Sidhe and we’re doing some of my material this Thursday at Shoreline Community College. We’re the 1pm band at SunFest 2017, at the Rock River outdoor theatre, on campus, near Building 1600.

While this is largely a campus event, there is bus service (331 from North King County, the 5 from the south, also… something like the 342 from Northgate?), and also visitor parking on the south side of campus, which it’s not expensive, and some street parking, which is free if you can get it.

Hope to see some of you there!

it’s the latest issue!

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!

Project Kohaku A-B-C

I made another thing! A magnetic (electric) Irish bouzouki pickup, the kind used on electric guitars, but with some extra features. I retconned a project name for it (Kohaku A-B-C) because it has three primary modes – “single coil,” “humbucker,” and “electric/acoustic mix,” which to be honest is kind of two modes depending upon the single coil vs. humbucker setting, but Kohaku A-B-C-D is too long and didn’t sound enough like a JDF anti-Godzilla plan.

Sounds!

Originally I was just going to do a basic wire-up with a level knob, but then I found out that humbucker pickups gave you separate access to both coils, and so can be used as a single-coil pickup as well as in humbucker mode. So that meant adding a switch. Which means it’s probably worth doing a tone knob while I’m at it. And while I was thinking about that I realised there was no reason I couldn’t also build in a tap to the extant acoustic pickup, which means I should also add a little mixer to control relative levels of the two pickups.

So I did! That was a good idea.

The two red knobs are the mini-mixer for the electric (left) and acoustic (right) pickups. Infinite relative levels! Or close enough. The two big black knobs are combined output level (left) and tone (right), the little switch is tone disable switch, the bigger switch changes the pickup mode – humbucker or single-coil.

I’ve had a bunch of those black rocker switches for a while, but I rarely use them because you need to cut a fairly precise rectangle for them to snap in correctly – there’s no screws or anything. Hearing that [CLICK] when you do it right and it pops into place and is straight and not loose at all or anything is so satisfying.

The pickup is held in place in the soundhole basically by foam and friction. Here’s the first test sitting, after I’d added the high-density foam to the pickup itself:

That was almost enough by itself, but not quite. I ended up adding a backplane and some spacer elements, as it had a tendency to rotate in place without those. The hot glue is mostly there to be cable stress relief:

The project box is an old Radio Shack room monitor transmitter – basically, a baby monitor. I don’t remember how I got it or anything. Regardless, I tested it a few years ago and it’d gone bad, so I gutted it and kept the cases for projects. I think it cleaned up well!

I can’t find a picture of a truly unmodified example, but I did find a decent picture with this mod where that modder kept the words “REALISTIC” and “FM WIRELESS ROOM MONITOR” on the box. I’d wanted to keep the REALISTIC logo, too, but I couldn’t – the knobs wouldn’t stay in place flat with the word still there, so I scraped it off with an xacto knife.

I did keep the big TRANSMITTER label though. That seemed important.

Here’s that little rectangular switch. [CLICK] into place. So satisfying. Looks factory. ♥

Here are the large-block components in place, without the wiring, and also without the tone knob bypass switch which was actually a later addition. (One that turned out unnecessary – 800K resistance and infinite resistance are pretty much the same as far as this tone circuit goes.)

The circuit itself is very simple. The larger switch controls which lead from the pickup (humbucker or single-coil) is fed into the electric pickup side of the mixer. The two mixer knobs are just straight-up variable resistance pots, as is the combined-output level control. The tone knob is based on the 1950s-1960s Les Paul-style electric guitar tone knob, only with a smaller capacitor which goes pretty well with the zouk. And the tone-knob enable/disable switch is just a ground lift on the far side of the capacitor and variable resistance pot.

Now I just need to find some way to make the controller stay attached to the face of the zouk (or any part of the zouk really) without making any change to the zouk itself. Maybe a suction cup?

I wasn’t even really thinking about that part when I started this project, past “keep it small so maybe if I want to think about it later, I’ll have the option.”

It almost looks like some kind of foot pedal, doesn’t it? The reason the controls are so large is just so they’re easier to grab without looking. I’m already controlling this thing by feel – if I can come up with some way to attach it, I think it’ll be legitimately viable as a stage device. It’s certainly no fussier than that piezo pickup I made for the octave mandolin, and I’m using that.

So – yeah! Kohaku A-B-C: much more fun than I expected. If you want to make one, Here’s where you can get the pickup bar, the only thing I bought new. The pots are all 1M variable-resistance linear pots, the single coil/humbucker switch is type SPDT and should be pretty clean since the signal goes through it, the capacitor is… 14nF film cap, because I had it and it was handy, and the tone bypass switch isn’t worth doing but if you want to regardless just use anything that’ll let you connect a wire to ground – it’s not in the signal path so you don’t have to worry about quality. The knobs were from the Radio Shack bankruptcy sale at 90% off, and since they’re going through another round of that now, maybe you can get some 90% off too. Or just use the metal posts for an industrial look, it’s not like you need the knobs.

As always, higher-resolution pictures are on Flickr. Have fun, and if you build it, let me know! ^_^

a user interface question

In an audio device with a tone knob, and an on/off switch by that tone knob, which “ON” makes more UI sense?

[poll id=”29″]

This is an honest question. I mean, I’m going to wire it up so that “ON” means “tone knob on,” because that’s how I roll, but I see this go the other way a lot.

(Also in this case “tone knob” means “low pass filter” which means “removes high frequencies” because AND THERE YOU GO. See? SEE?)

“kohaku” electric test harness nr. 1

Literally the first signals off the electric test harness for Kokahu.

Recording is from a couple of days ago. There have been meaningful additional developments since this, but this is what I’m posting now.

How many electric Irish bouzoukis are there in North America? One more than before last week.

More to come.

a late addition to an old report

Remember a long time ago – like, a little over three years ago – I built a ribbon microphone? I had all kinds of problems chasing radio interference ghosts and stuff, it was strange and messy but came out with a neat sound in the end.

Except… even after fixing the RF problems, it was kind of noisy. Not unusably so, not for direct-miking, which is how I’ve used it, but still… kinda noisy. Noisier than it should’ve been.

I rediscovered this when trying to use it in a “mid-side” type mic setup with the new RK-47, which I was doing just to see how that would work. (Tony of Vixy & Tony has been after me to try that for a while.) And because it involves playing towards a figure-eight microphone from the side – the point of least sensitivity – it required enough extra gain that the noisiness became a problem.

Since the special preamp (also a kit) was the entry point for the RF noise, and since said amp works with dynamic microphones, I tested that for noise, using an SM-58 as input. Dead silent, cranked all the way up. Result: it wasn’t the microphone preamp’s fault.

Then I remembered how the RK-47/990B build manual talked so much about making damn sure you had no solder rosin or finger oils at the high-impedence connection points in the circuit, and to just scrub those connections with isopropyl alcohol. So I took apart the ribbon microphone, redid those solder connections while I was in there, and then scrubbed the hell out of them. A downright confusing amount of old solder rosin came up when I did so.

Result? Problem sorted. Huge drop in noise. There’s still a little at the high end at probably more gain than I even need here – this may be an “only elves can hear this” moment, at least in part – but a little -3db cut starting at 14-15kHz sorts it. It might not even be true noise, it could be something like air movement – ribbons will pick that up in ways nothing else will, and I didn’t turn off the HVAC, etc.

So, yeah! Turns out that finicky bit about solder rosin and flux is real important, kind of generically, at high impedance. Good to know. (And is why I’m posting this, and why I’ll link to it from the old microphone buildout writeups.)

I still have not the vaguest idea why so much rosin ended up on those connection points. Seriously, it’s weird. That was my old stock of Radio Shack silver solder, which I’d had since I Don’t Even Know When, and not the BenzOMatic solder that gave me so many problems. I never noticed it doing that before – but then again, I wasn’t really looking. ¯\(ツ)/¯

Anyway, have a test recording I made at 1:30 yesterday morning trying out that configuration, with the Micparts RK-47/990B kit mic being used as the “mid” and the above-mentioned Austin OTA-1 ribbon microphone as the “side.” It’s intermixed with a recording made simultaneously using a pair of M-Audio Novas in a spread X-Y configuration. Both versions are mixed directly to mono, rather than spread-stereo, which is not what you usually do, but does allow maximum left-right placement in a mix.

(This may be called “T” rather than “mid-side” since mid-side includes a kind of subtractive mixing not used here? I dunno. But this is, again, just a straight mix to mono.)

The recording starts with the RK47/990B plus OTA 1 pair, then switches back and forth between that and the Novas. Remember: all of this is mono.

Kinda neat, eh?

let’s listen to an rk-47 microphone!

Build reports are nice enough. (I wrote up a little errata post yesterday, by the by.) But the real question, of course, is how does the RK-47/990B kit mic sound?

Early impressions are surprisingly good. Even with only the single microphone, there’s a sense of presence and space – even with a purely mono signal path – that I normally have to dual-mic to attain. Also, it has tremendous precision – this is a mic capable of great subtlety. And the amount of gain built into the microphone itself is crazy – this is one spicy meatball of a microphone. That’s something you won’t hear in recordings, but it results in a lower noise floor, which is always good.

Let’s start with some unsubtle differences, ones that’ll show up on laptop speakers. Because while I’ve never liked the MXL-990, they sell a zillion of ’em, and we should make a couple of direct comparisons.

Here’s a snippet of chords from “Lukey,” alternating between the MXL-990 (unaltered factory) and the RK-47/990B. It starts with the MXL-990, then transitions in-song to the RK-47, then back and forth. It ends with the RK-47. It’s a pure mono signal path until prepped for uploading to Soundcloud.

And here’s a short melody, on zouk – again, starting on MXL-990 (factory stock), then RK-47, then back to MXL-990. The last phrase is repeated to allow us to end on the RK-47; also, I wanted that ending bit to be presented on both microphones. The glissando really highlights some of the differences.

But that’s shooting fish in a barrel, as it were. The MXL-990, while popular, is not a good microphone. We should do comparisons to microphones I actually like – let’s say, the M-Audio Nova. At about twice the price of the MXL-990, it’s still a cheap microphone, just one I consider entry-level competent. But it has issues – not the least of which being it’s kind of a noisy beast as these categories of microphones go.

So let’s take the easy swing – here’s a sharply boosted noise level comparison of the RK-47 to the M-Audio Nova, at equivalent gain levels. This is not the noise you’d actually hear; I recorded a silent room at gain appropriate on each microphone for instrument recording, then cranked that recording up 32db for easy noise levels comparison.

Unfortunately, this really requires headphones, because it’s RK-47 on left, Nova on right:

NOT SUBTLE. But also, an easy shot. The Nova is noisy and everybody knows it. There are some mods out there to improve that, but they change the sound a bit in ways I don’t like, so I work with it.

comparison of waveformsSo let’s dig down a bit. Pictured here is a snippet of waveform from a bit of music played, in mono, over my studio monitors, into identically positioned microphones relative to those speakers. These two recordings were made simultaneously.

You’ll note in this highly-zoomed-in render how the RK47 waveform remains clear and unmuddled in these extremely rapid changes, while the Nova’s blurs into a bit of a mush. That’s the sort of thing I’m talking about, and also, the sort of thing you can hear in these very short snippets of horns from a jazz track. This comparison requires headphones, possibly good ones:

They’re short because they must be uncompressed for best comparison – sorry about that – but listen to them a few times and compare. Note how the edges of detail – bits which add flavour – are blurred in the Nova, but retained in the RK-47. Neat, eh?

That out of the way, let’s step up a level in comparator microphones. Oktava 012s are considered very good affordable microphones, particularly strong in their price ranges, and street for a new 012 and one pickup is comparable to the cost of this kit. With a second head (to add a second pickup pattern, as this mic has), it’s a bit more. They’re small-can capacitor instrument mics, rather than large-can, but we’re doing instrument recording, so that’s fair. The components inside – particularly older ones picked up used – can be a bit dodgy, but the design is great and the pickups are great, and you can upgrade the iffy capacitors and the suspect transistor if necessary. I have, of course, done this with mine.

Here’s the intro to “King of Elfland’s Daughter,” on the Oktava 012 (upgraded components) and the RK-47/990B kit. This recording repeats phrases, with the Oktava 012 first, then the RK-47/990B. Pure mono signal path, identical recording setup made within a few minutes of each other, but not simultaneously, as you can’t put two microphones in exactly the same place and I wanted the most equal comparison I could, modulo performance limitations. This probably also requires headphones, as the 012 is a pretty darned precise microphone itself:

44.1khz/16-bit uncompressed WAV file version here.

Once again, I’m finding that the RK-47 has a real staging advantage. There’s a sense of in-the-room presence with the RK-47 that I can make happen by dual-miking with my other microphones and mixing down, but not directly in mono.

Now, I don’t want to leave the impression that it is BEST AT ALL THINGS, because it’s not. These aren’t the only recordings I made – they’re just ones that show differences best. The first example I found was mandolin – the Nova likes my mandolin better than the RK-47 does. The specific response behaviour and foibles of the Nova work in its favour; a single RK-47 may have more presence and precision than a single Nova, but the Nova recording sounded more musical just the same. I’m sure there will be other examples as well.

In the end, I think this will probably become a heavy-use microphone in my kit. It may even become my go-to mic on the zouk – I need to do some stereo and multi-distance comparisons before I will know that for sure, but it’s looking very good. I also like what it does with piccolo and flute. I haven’t done any playing around with fiddle or drums, and one thing I want to play with is a two-mic setup with the ribbon kit mic I built, to see how those behave together – it’s a mic placement technique I’ve wanted to try for a while, but have never got round to testing. Now is probably the time.

I kind of wish I’d ordered the matched-pair version of this microphone kit. But it would’ve cost twice as much and I couldn’t know in advance I’d like it this much, so.

a bit of errata for the rk-47 build report

A bit of errata on the micparts rk-47/990B kit microphone build report yesterday:

First, I didn’t mention that the board kit includes extra capacitors, to be used either for different capsules than I chose, or to tailor the response curve of the microphone. I went for flattest response, but I could’ve had more or less high-end responsiveness by choosing which included tone capacitors to use.

Second, I said that the “omni” switch setting probably wasn’t really going to be actually “omni,” but was more likely to be figure-eight or the like. This was in response to both the capsule design, grille design, and older pictures of the circuit board which appeared to indicate that. In testing, I discovered that I was mistaken – as you can see here, levels as seen in waveforms made by holding a tone generator at the four cardinal directions remain constant. But read on, after the graphs, because there’s a catch:


rk-47 set to omni, against tone generator at 30cm, front, right, rear, left positions

And here’s the same test, with the mic set to cardioid:


rk-47 set to cardioid, against tone generator at 30cm, front, right, rear, left positions

And here’s an M-Audio Nova, same conditions, for comparison:


nova, cardioid, against tone generator at 30cm, front, right, rear, left positions

The total pickup is certainly omnidirectional. But this is not a true basket head on this thing, there are support brackets on the left and right sides, and that does affect tone! High-end harmonics definitely fall off on the left and right sides.

So while it does qualify as an omnidirectional microphone in “omni” mode, I’d have to call it flawed in that mode, and use something else – like an Oktava 012 with the omnidirectional head, which is built for true omnidirectional pickup and does not exhibit this behaviour.

Alternately, I suppose it might be usable in that mode if you’re recording someone who is a tad screechy – aim the wrong side at the performer and presto, fewer high harmonics. EVERYBODY WINS XD

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