Random looping 16-step sequences

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Tombola
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Post by Tombola » Thu Feb 02, 2012 7:23 am

neilbaldwin wrote:Slightly off-topic: from a friend on here I know what your 'proper job' is so I was wondering how you ended up with electronics skills? Self-taught? I only ask because I find your stuff inspiring - it's where I'm trying to get to with my DIY, in very small frustrated steps :hihi:
Totally self taught, and half-assed - taking bits of different circuits, connect them together, fiddle until they work long enought to make a video. Couldn't explain Ohms law. First project was this: http://musicthing.blogspot.com/2008/10/ ... first.html

There is so much information and help out there now - http://www.beavisaudio.com/ got me into the basics of building stompboxes, then this DIY forum and electro-music. Been doing stuff for Euro for about a year.

Always amazed at the quality and insight available - was trying to learn about the Buchla Source of Uncertainty, and this thread: http://electro-music.com/forum/viewtopic.php?t=30861 just goes through and dissects it, talking through the different bits, how they work.

The more you learn, the more you appreciate the genius of Don Buchla, Serge Tcherepnin, Stanley Lunetta, Peter Zinovieff, Bob Moog, Blacet, Ken Stone, Grant Richter etc etc, coming up with all the ideas we're still working through today. How they came up with this stuff while working 40 years ago without the internet, without overnight parts delivery, without cheap chinese PCB fab houses, amazes me.

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Post by Navs » Thu Feb 02, 2012 12:09 pm

papercutnoise wrote:Been dying to see a schematic since I first read about this on Nav's. Count me in for a pcb too :)
The schematic is here: http://cgs.synth.net/modules/cgs13v2_ga ... rator.html

I left out the comparators, LED drivers, stage switches and inverted output. It's fairly simple, but fiddly depending on how big you want your board to be.

Tom has added some nice twists like the LED display, DAC (which is great because laying out and soldering the R2R ladder was :bang: on Bitsy) and a couple of switches for manual loading of data. I really like the latter idea, but agree with Tom - the point isn't to sit there programming sequences in binary :lol:

There's a couple of things I would change if doing a Bitsy mkII, like adding the input comparators, at least for the data. I've noticed with the WB that at slow speeds, the burst pulse might be too short to get recognized, for example. I'd also add manual input buttons and a rotary/ click switch to shorten the stages to give odd length sequences.

There's more info linked here: http://navsmodularlab.blogspot.com/2011 ... order.html

The Klee & Rungler links are of particular interest.

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simfonik
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Post by simfonik » Thu Feb 02, 2012 12:21 pm

I'd love a PCB if it happens.

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Post by jimmyambulance » Thu Feb 02, 2012 4:56 pm

want.... for real....

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neilbaldwin
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Post by neilbaldwin » Thu Feb 02, 2012 6:39 pm

Tombola wrote:
neilbaldwin wrote:Slightly off-topic: from a friend on here I know what your 'proper job' is so I was wondering how you ended up with electronics skills? Self-taught? I only ask because I find your stuff inspiring - it's where I'm trying to get to with my DIY, in very small frustrated steps :hihi:
Totally self taught, and half-assed - taking bits of different circuits, connect them together, fiddle until they work long enought to make a video. Couldn't explain Ohms law. First project was this: http://musicthing.blogspot.com/2008/10/ ... first.html

There is so much information and help out there now - http://www.beavisaudio.com/ got me into the basics of building stompboxes, then this DIY forum and electro-music. Been doing stuff for Euro for about a year.

Always amazed at the quality and insight available - was trying to learn about the Buchla Source of Uncertainty, and this thread: http://electro-music.com/forum/viewtopic.php?t=30861 just goes through and dissects it, talking through the different bits, how they work.

The more you learn, the more you appreciate the genius of Don Buchla, Serge Tcherepnin, Stanley Lunetta, Peter Zinovieff, Bob Moog, Blacet, Ken Stone, Grant Richter etc etc, coming up with all the ideas we're still working through today. How they came up with this stuff while working 40 years ago without the internet, without overnight parts delivery, without cheap chinese PCB fab houses, amazes me.
Good stuff Tom, thanks for the insight. :)

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Spandex
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Post by Spandex » Wed Feb 08, 2012 3:18 pm

Tombola wrote:
Monobass wrote:very nice Tom, is this another Arduino/ATMega based project?
No, this is proper hardware - a few CMOS chips.

Problem with software is people come over and crash it when you're doing a demo!
8_)

Great project.

Do you find it often has a certain character - like the Noisering - of a particular ascending or descending seq? Cos if yr bitshifting left, yr effectively multiplying by two and any new deviation is always in the LSB. If u shift right then yr halving it - but with the option of adding a new MSB - to bump it up an order of binary magnitude. I reckon I can hear this in my Noisering... am I way off? Do u hear it too? Does it make it more musical? Cos it's nothing like random. There are, by definition, only two values that can follow any other. Keep going over this in my head :) is it right?

I've wasted literally months of my life building these kinds of circuits virtually on NM and G2. Slowly morphing seqs basically. They use very little DSP - but loads of modules. Kept hitting the limits of memory while the DSP was barely ticking over :/

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Post by JJ » Thu Feb 09, 2012 1:54 am

Great stuff! Would love to build this into my euro! :yay:

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Post by Tombola » Thu Feb 09, 2012 2:37 pm

@spandex - yes, I know what you mean - it definitely 'rises' at the start - ie going from a 00000000 to 10000000 to 01000000 and so on. However, once it's a stream of really random 0s and 1s, it shouldn't be so obvious

And you can see in the video with the 'scope that there is some very non-random stuff at the start - fast rise, slow drop off. I'm not sure if this is flaky breadboard bleed/noise, non-random Random input (I think I was using the wogglebug burst out at that stage, which is anything but consistent white noise) or something inherent in the system.

The Noisering is called a data resonator - I wonder if there's some way to use the 'decay' after a bunch of 1s like a ring or reverb at high clock rates?

Next thing I'm trying to add - don't know if it will make it to a proper prototype - is a system which takes the 8 channels of shift register output through 8x switches (2x 4016 switches, voltage controlled somehow) and into another DAC, to provide variations. This is roughly how the QRV section of the Buchla 266 source of uncertainty works, I think.

in the G2 editor you can do this by switching channels in and out of the DAC. It's quite musical, feels a bit like dropping notes in and out of an arpeggio - http://soundcloud.com/musicthing/shift- ... encer-nord

Since starting this, I've been listening to Keith Fullerton Whitman's Generator album, basically i'm trying to build that in a module...

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Spandex
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Post by Spandex » Thu Feb 09, 2012 4:33 pm

The bitswitching idea is really interesting.

With any design based around bitshifting - you're always gonna have that limiting thing of any value only having two possible "descendents". I don't think that's a criticism tho... the two possible values are always somewhat distant from the current value and i think that's what makes these devices good. Truly random distributions would be "clumpier" and maybe less interesting musically.

I guess you could look at what different switched bits might do.. it's much harder to imagine without writing stuff down :) you'd still only have two possible t+1 values at each t... maybe it wouldn't be as good?? maybe it'd be better.

Using G2 to prototype these things is an excellent idea.. might go play now.

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Post by Spandex » Thu Feb 09, 2012 6:05 pm

I've been playing... thought the best way might be to see the randomness visually... so I wrote a quick prog to render a few things.

From left to right..
1) Random (or as random as the psuedo random number generator on my machine is - good enuff for this)
2) Bitshifting. Guaranteed new bit each rotation, random choice of 0 or 1. If it was a NoiseRing it'd be Change 100% clockwise and chance at noon.
3) as 2 but with the bits switched to this order before "DAC" - 73210465
4) as 2 but with the bits switched to this order before "DAC" - 23745610

There's two views of each so u can see the randomness at different scales.

Image Image Image Image

Image Image Image Image


If I had to choose one of those for my wallpaper.. I wouldn't choose the first column. the others are clearly random-ish... but with a wee bit of structure.. they look more.. um.. natural??

What's really interesting* though is that your idea of swapping the bits round under CV control looks like it could be really good for giving the randomness particular "characters".

This is how I spent my Thursday evening. WHO WANTS TO COME PARTY AT MY HOUSE WITH THE EVER-SO-SLIGHTLY DIFFERENT IMAGES? :party: :party: YAY! GREYSCALE FTW! :guinness:

*may not actually be interesting

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Post by Tombola » Thu Feb 09, 2012 6:20 pm

Here's one version of the CV-controlled 'shuffling' in Nord
http://dl.dropbox.com/u/1543473/logicswitcher.pch2

In this case it isn't actually shuffling, just turning bits on and off.

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Post by Spandex » Thu Feb 09, 2012 6:48 pm

Nice.. I modified it to shuffle.. there's two shuffle stages in series.. one just swaps each pair of bits.... the next stage is a bit wilder.

Can turn each stage on/off independently... with both off, you get the original signal, obv.

http://dl.dropbox.com/u/3839475/logicsw ... andex.pch2

Incidentally.. i hit the memory wall again while playing with this.. was putting in a load of 8->1 and 1->8 mux/demuxers... and ran out of patch RAM when I was still under 50% of the DSP in a single slot of my fully expanded (i.e. 800% total) G2. ridiculous :)

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Post by Tombola » Fri Feb 10, 2012 5:08 am

Another proto - here's a proper Voltage Controlled switch - which shuffles the bits - i.e. puts them back in a different order.
Not totally sure about it now.
http://dl.dropbox.com/u/1543473/vc-swich.pch2

One thing I really miss on the Nord is a Quantizer with a trigger out, like the A-156 - that would be really helpful in this context

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Post by Spandex » Fri Feb 10, 2012 5:39 am

Tombola wrote:One thing I really miss on the Nord is a Quantizer with a trigger out, like the A-156 - that would be really helpful in this context
Yeah... v annoying. wish they'd kept up dev on that machine, it'd be so easy to add that feature in software.

i've built something like this on the G2 though (or maybe on the NM, thinking about it.. but the NM2G2 patch converter is excellent). I'll see if I can dig it out later.

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Post by Spandex » Fri Feb 10, 2012 9:15 am


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Post by Spandex » Fri Feb 10, 2012 9:41 am

Tombola wrote:Another proto - here's a proper Voltage Controlled switch - which shuffles the bits - i.e. puts them back in a different order.
Not totally sure about it now.
http://dl.dropbox.com/u/1543473/vc-swich.pch2
Right.. just had a looks. I can see why you're not sure.. but what you're doing there is just switching bits on/off.. so you're just introducing incontinuities. What's more, you're switching them off sequentially from one end, so you're introducing incontinuities in the most boring order tbh :) ... coming close to just dividing by two for each turn of the knob.

So your thing would turn 255->127->63->31->15->7->3->1

Whereas if you turn them off in a different order you could get

255->191->175 etc etc..

But more interesting still would be to swap the bits, as in my G2 example above (and in my slightly different, grey PNGs:)). Then you keep the full range of the DAC, but you've munged the values into a different character.

If you imagine you've got a locked loop (no new data).. suddenly your VC of bitswapping is giving you a load of "variations".. where you can always get back to the previous pattern by giving it the same voltage as before.

That's technically true of your logical AND... but the patterns will always go up and down in the same places.. they'll just have the bit mask subtracted from the value at every point.

Get swapping instead of ANDing and you're in a whole new territory of brilliantness IMO.
Last edited by Spandex on Fri Feb 10, 2012 9:50 am, edited 1 time in total.

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Post by Spandex » Fri Feb 10, 2012 9:42 am

Did i just say "incontinuities" ?

If you turn this into a module, please label the VC shuffle input "incontinuity"

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Post by Monobass » Fri Feb 10, 2012 12:27 pm

"...but on this module the incontinence goes up to ee-lev-en. it's one louder."
Thonk - CLICK HERE - Modular Synth DIY + Eurorack Accessories Store

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Post by Tombola » Fri Feb 10, 2012 1:55 pm

VERY interesting: Grant Richter talking in the malekko forum:

"The "Cybernetics" expander adds the stuff from the 266 that I originally left out. Anyway, the expander adds variable psuedo-random microsequences, big and little endian individual bit switching, random gate and trigger and a chromatic quantized output. "

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Post by Monobass » Tue Apr 17, 2012 2:43 am

on a pcb!

Image

http://instagr.am/p/Jfx71sjmSH/

(btw, that was me on Twitter Tombola)

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Post by Tombola » Tue Apr 17, 2012 3:03 am

Yes, it's very nearly working perfectly - something went wrong with the loop/random pot, but I think I know what the problem is.

Pm me if you want to beta test the v1 PCB - I have more than I need. Parts are mostly straightforward - chips are all CMOS - got them & the LED from Bitsbox, switches and resistor network ( which you could bodge around) from Rapid. Only fiddly bits are the erthenvar 3.5mm sockets and the vertical alpha pots from Banzai. I thnk the pots are going to be too short for knobs...

I'm planning to do an acrylic panel in the next week or so

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Post by Boofin Moonrocks » Tue Apr 17, 2012 3:10 am

Woah, this looks like it's gonna be a super cool project! I'm really excited to try this out once the boards are done!

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Post by simfonik » Tue Apr 17, 2012 10:10 am

Nice to see things coming along on this project.

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Post by Emalot » Tue Apr 17, 2012 1:52 pm

Tombola , you'll do Boards run??
When?
:bacon: :bacon:

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Post by Tombola » Thu Apr 19, 2012 5:30 am

Hmm....

Image

Needed a pretty ugly cludge to get this one running perfectly - one trace cut, 3 wires soldered between pins.

I'll finish the panel and make a demo video to judge whether there is any audience for a v2 PCB.

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