Tips on sine-width modulation

Veets · 2013-10-20T16:02:36.000Z

I was asked about the details of sine-width modulation in another thread. The basic idea is you cut up a sine wave into two pieces. One half is “squished” and the other is “stretched” relative to the original wave. This is the same thing as pulse-width modulation of course. However, very few synths do this as far as I know. I have been told that the Casio CZ series from the 1980s can do this and that this is a kind of Phase Distortion synthesis. So it’s cool that the Mono can get it on the fun.

Well, how to do it. I used Wavosaur which is a free WAV editor. I started with a 200 hz sine wave. You can tell Wavosaur to make this in the Tools>Synthesis menu option. You can set the sampling rate to 40000 hz so that it is “cleaner” with regard to a 200 hz wave.

Make one cycle which is 1/200 seconds long (0.005) seconds. This is the base wave. The base wave has an “up” portion (0.0025 seconds) and a “down” portion (0.0025 seconds). Save the base wave to your hard drive. You can call it “S200.wav”.

It is easier for the following waves if you have a spreadsheet program like Excel.

For the next wave, we can make the “up” portion be one octave higher, 400 hz. You can calculate in Excel that a 400 hz wave is 1/400 seconds and that the “up” half of that is 0.00125 seconds. Copy the up portion in Wavosaur and paste it into a new file.

We now want the “down” portion to be long enough to make the whole wave 0.005 seconds. So calculate 0.5/(0.005-0.00125) = 133.33 hz. The 0.5 is in the numerator because we only want the down half. Use Wavosaur to synthesize a 133.33 hz wave and then copy the down half. Paste that behind your up portion from the previous step. You now have a sine-width modulated waveform. Save your file. You can call it “S400.wav”.

From here on out, you can do this as many times as you want. You can do another octave or two and/or you can fill in the gaps between the ones you already have. The more that you do, and the more gradually that you do them in terms of pitch, the smoother your “interpolations” will be. Also, you can consider different “rules” for how to fill in the gaps. I did equal-spacing but this is not required. Depending on how you generate these waveforms, your sounds will come out to have different tonalities.

When you are done, you upload the WAVs to the Digipro. Make sure to send them in the logical order based on the frequency content. For example, make sure the S200 goes in the first slot, then S400 in the next, then etc.

Now program the Mono’s LFO to cycle through the different waveforms at the speed you like as in the video. There is a time parameter on the Mono which smooths out the transitions, but you may also like to leave this off for a “steppy” sound. I used the triangle LFO to make it sound like a classic pulse-width modulation but you can use whatever shape you like. You can also control the depth of the LFO so that it only uses the waveforms closer to the base wave. This will give a very warm sound to your Monomachine. Another thing to try would be to have the LFO reset on every trig. This could give a sharp attack and warm body or vice versa.

FreeFall · 2013-10-20T19:19:53.000Z

And I thought I was just going to cut up some waves (visually) in a DAW. Ha! This “calculation” of waves stuff is waaay beyond me (What can I say? I’m a Graphic Designer, not a scientist).

This is actually the perfect example of why it would great if Elektron provided some sort of tutorials in regards to this more esoteric stuff, geared towards the average human being. I know this stuff is probably very simple for the brainiac programmer types, but for the rest of us, the User Wave feature will be left as is from the factory, and that’s a real bummer after seeing the great sounds you got out of using it VEETS.

It would AWESOME if Elektron actually released some single cycle wave packs. It would be a great help for those of us who are less scientific but still want to take advantage of these capabilities of the machines. To be honest it’s a little disappointing that Elektron hasn’t offered anything like this. I mean, they put out sample packs for the OT and some “booster packs” of preset Kits and Patterns for the MnM (I’m not interested) but not a single solitary pack of SCW’s or cool wavetables.

I did download a shit ton of single cycle waves from this guy ‘Adventure Kid’ (http://www.adventurekid.se/akrt/waveforms/), and I have loaded some into my MnM. But unfortunately, the way he named the wave files makes it impossible to determine what wave you have selected (all wave names begin with “AKWF”). I renamed a bunch of them so they would at least appear with a different name when loaded in the synths, but that got old real quick. He also has hundreds of ‘other’ waves with no indication as to what they are at all, so it’s just a shot in the dark as to what you spending your time loading into the MnM. It’s great that he put all those waves out to the world for free, but … (sorry to ramble on)

Regardless, thanks for all the in-depth information VEEETS. You rock for putting the tutorial and info together for everyone.

sicijk · 2013-10-20T21:25:17.000Z

Thank you sooo much Veets!

so…should the sines (after the 200Hz) look something like this?

Furthermore…the default output volume for the wave is 0 dB and i noticed that the actual resulting waveform is plenty of harmonics.
So maybe I’ll try with another batch lowering the final output.

What is your setting?

Veets · 2013-10-21T15:39:57.000Z

@sicjik, That’s it - you have it perfect! I think I went up to 800 hz and then did some intermediate values. That’s an interesting idea about lowering the output volume a bit. There might be some clipping in the Mono. I didn’t really notice it but you never know. Mine are all normalized like yours.

@Freefall, sorry if I overexplained. You could cut them up in a DAW too. In fact that is an interesting idea. Take a sine wave, trim off the end gradually in small amounts. Hmm… gonna have to try that one someday, I imagine it will sound interesting. Anyway, maybe Sicjik’s picture is more helpful for a visual representation? If you do his wave, and then cross fade with a sine wave, you will have the same idea. Once you do two, you can do more if you like.

Actually, you probably don’t really need the formulas…you could do them all by eye. I just used the formulas to make them have a certain spacing. But if you do it your way, you will have a custom version. There’s no right way, just fun ways

@phading Sure, I will work on uploading the files in the next couple of days. I’m kind of slammed this month so it might be a bit.

FreeFall · 2013-10-21T17:21:13.000Z

@Veets

Excellent. I’m gonna give it a go in a DAW then.

I actually spent several hours yesterday (Sunday) batch renaming the wave files from the Adventure Kid web site, and uploading them into my MnM. I even made a few banks that contain an assortment of wave types for “wavetable” sweeping fun!

Thanks again for your help Veets.

Veets · 2013-10-24T15:58:26.000Z

Sure thing guys. And here are those waveforms. Send 'em in alphabetical order starting with S202.wav going up to s245.wav and then lastly s200.wav. I guess I didn’t alphabetize the last one for some reason. You can also look at them in Wavosaur. Pretty simple once you take a look.

http://www.sendspace.com/file/2a35ed

FreeFall · 2013-10-24T17:51:02.000Z

Thanks for the waves Veets!

Very generous of you.

BoomTish · 2013-10-24T23:52:37.000Z

Veets delivers again Thank you

Veets · 2015-11-05T05:18:57.000Z

Hey does anyone still have these files? Someone PM’d me about them and I have searched two computers to no avail. If you have them, could you re-up them? Thx!

Veets · 2015-11-06T01:28:32.000Z

Dub comes through - here they are, for the moment anyway.

https://www.sendspace.com/file/0hnfs3

PeterHanes · 2015-11-07T02:29:52.000Z

""Veets"":

Dub comes through - here they are, for the moment anyway.

https://www.sendspace.com/file/0hnfs3

Thanks for re-posting!

Veets · 2015-11-11T16:26:11.000Z

Happy to. And big thanks to Dubathonic for the save!

funqpatrol · 2016-08-06T22:51:19.990Z

Hi guys, great tip and awesome sound! Any chance some of you could share the waves again? The links are dead. Thanks!

dubathonic · 2016-08-07T12:54:38.587Z

i’m on travel right now, but remind me in a few days if you don’t find them elsewhere, i can send them to you.

(as soon as elektron reinstates the files section i’ll upload them there as well.)

Veets · 2016-08-07T19:26:46.831Z

Thanks Dub - I hooked him up.

Safe travels D.

Veets · 2016-08-07T19:33:47.840Z

So one of my fave patches from that set is the lead sound around 3:05. In case anyone is wondering, here is how to do this (from memory). Pretty sure I set the LFO to begin with one of the “sine-ier” waves and then LFO over to one of the more “sine-widthy” waves and then LFO back. So you get a smooth attack sound which then gets some more bite and then mellows out. Add a little reverb/delay to taste.

magneteyez · 2016-08-07T19:37:41.027Z

Any chance to up the files again? I can host them in my Box account. That way they’ll be up forever (at least as long as I live ;-))

Veets · 2016-08-07T19:40:57.475Z

PM sent.

magneteyez · 2016-08-07T20:18:47.055Z

The waves can be downloaded from here:
https://app.box.com/s/joaker3btb61dm6i4htfhvm4hz22kibp

funqpatrol · 2016-08-08T13:33:22.932Z

Thanks Veets for the files here they are again: https://dl.dropboxusercontent.com/u/14949737/Elektron/s220.zip