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Fritz chaos circuit
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andrewF



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PostPosted: Fri May 04, 2007 2:08 am    Post subject: Fritz chaos circuit Reply with quote  Mark this post and the followings unread

i just finished this one today.
it is one of the most 'out there' modules i've ever tried and an easy build.
nothing at all like usual random voltage generators.

i'll try and get some samples and scope shots up in the next few days
but there are some on Ian's site -


http://home.comcast.net/~ijfritz/ch_cir1.htm
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Uncle Krunkus
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PostPosted: Fri May 04, 2007 3:08 am    Post subject: Reply with quote  Mark this post and the followings unread

That looks bloody brilliant. Why didn't I think of it? Rolling Eyes
Definately going on my "to do" list, which is actually wrapped in barbed wire these days. Laughing

BTW It actually a perfect Lorenz attractor. Somebody was building one of these on the G2 just a week or so ago.

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fluxmonkey



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PostPosted: Fri May 04, 2007 7:15 am    Post subject: Re: Fritz chaos circuit Reply with quote  Mark this post and the followings unread

andrewF wrote:
i just finished this one today.
it is one of the most 'out there' modules i've ever tried and an easy build.
nothing at all like usual random voltage generators.

i'll try and get some samples and scope shots up in the next few days
but there are some on Ian's site -

http://home.comcast.net/~ijfritz/ch_cir1.htm


ditto: i finshed mine wednesday, and blew all last night exploring and still felt like a was scratching the surface! particularly liked utilizing the relationship between the 3 outputs... similar but not identical modulations about 120degrees out-of-phase. try CVing 3 separate oscillators w/ the 3 outputs, panned left/center/right, nice spatial effect.

life is good.

bbob
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bubblechamber



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PostPosted: Fri May 04, 2007 5:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

this thing looks great...what did you guys use for opamps?
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fluxmonkey



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PostPosted: Fri May 04, 2007 6:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

bubblechamber wrote:
this thing looks great...what did you guys use for opamps?

i don't think it's critical, TL071, TL072 are fine
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bugbrand



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PostPosted: Fri May 04, 2007 6:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

Those lissajous sort of scope patterns on the linkpage look really amazing. I must build one.
Thanks for the link & notice - great project.

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frijitz



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PostPosted: Fri May 04, 2007 8:55 pm    Post subject: hey that's me Reply with quote  Mark this post and the followings unread

Hello. I've been thinking about dropping by, then I heard you were talking about me.

I have boards for each project available. Please e me if you would like to get one.

Oh, and it's not a Lorenz attractor at all, although both systems have the double scroll.

Hope I can figure out how this forum works.

Ian
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fonik



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PostPosted: Sat May 05, 2007 2:52 am    Post subject: Reply with quote  Mark this post and the followings unread

hello mister ian fritz, can't believe it you are here...
welcome

i am currently working on the double pulse waveform generator - i will get back to you soon, i guess!

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elektro80
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PostPosted: Sat May 05, 2007 4:00 am    Post subject: Reply with quote  Mark this post and the followings unread

Ian Fritz, welcome


salut salut salut

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Blue Hell
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PostPosted: Sat May 05, 2007 4:22 am    Post subject: Re: hey that's me Reply with quote  Mark this post and the followings unread

frijitz wrote:
Hope I can figure out how this forum works.


I just browsed throught your web site, you'll manage here Very Happy Interesting site Exclamation

Was wondering if you have any sound samples for the circuits you present - especially for the clarinet related things - but I'm also curious about analog atractor circuits as I tried to model things like it on the Clavia G2 synth. Would be interesting to me to compare digital and analog here.

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Uncle Krunkus
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PostPosted: Sat May 05, 2007 5:32 am    Post subject: Re: hey that's me Reply with quote  Mark this post and the followings unread

frijitz wrote:
Oh, and it's not a Lorenz attractor at all, although both systems have the double scroll.


How does it differ from a Lorenz attractor?

Oh, and a big - Welcome to electro-music.com! Very Happy

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v-un-v
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PostPosted: Sat May 05, 2007 6:57 am    Post subject: Re: hey that's me Reply with quote  Mark this post and the followings unread

frijitz wrote:
Hello. I've been thinking about dropping by, then I heard you were talking about me.


Cool

I'll get the kettle on! Very Happy

welcome to electro-music.com Ian! Very Happy

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PostPosted: Sat May 05, 2007 6:59 am    Post subject: Re: hey that's me Reply with quote  Mark this post and the followings unread

frijitz wrote:

Hope I can figure out how this forum works.


The straitjacket is optional! Shocked Laughing

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IST NICHT FÜR GEWERKEN BEI DUMMKOPFEN. DER RUBBERNECKEN SIGHTSEEREN KEEPEN DAS COTTONPICKEN HÄNDER IN DAS POCKETS MUSS.
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Scott Stites
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PostPosted: Sat May 05, 2007 8:32 am    Post subject: Reply with quote  Mark this post and the followings unread

welcome Ian, It's really great to see you here!!

I may be missing them on your new website (since you changed servers), - are your windcontroller samples still there?

Seriously, those were some of the most beautiful synth samples on the net - the level of expression you were able achieve was astounding!

Best Regards,
Scott
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frijitz



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PostPosted: Sat May 05, 2007 12:10 pm    Post subject: Thanks for the welcome! Reply with quote  Mark this post and the followings unread

This looks like a really interesting bunch of folks. I'm going to answer several messages at once -- hope that's OK.

Bubbles -- Op amps aren't critical for the EZ Chaos circuit. I used TL072 and LF351. The circuit runs slow, and noise isn't much of an issue in a chaos circuit. The only possible limitation would be at the low speed end, where a lot of bias current could hurt you. But any general purpose bifet should be fine.

Fonik -- Always glad to see someone working on waveshapers. This is one of my favorite areas. Are you using the double pulser from my site, or the old Electronotes one? I have several versions of this, and it has probably been my most used timbre shaper over the years. Check out the 5Pulser if you want to see a really radical shaper. I've spent a lot of time looking for a shaper that would really give huge spectral variations, and so far this is the best!
http://home.comcast.net/~ijfritz/sy_cir8.htm

Blue -- Yeah, clips are scattered around. Nothing for the clarinet, since it ended up bein basically a rounded square wave. For the chaos clips start here and then drill down.
http://home.comcast.net/~ijfritz/ch_over.htm

Uncle -- The Lorenz system is autonomous (self-oscillating) and involves a couple of multiplications. There is a circuit by Paul Horowitz you can Google for. The Double well system is an externally driven system, with a different nonlinearity. I've avoided multipliers by using zener diodes for the nonlinear response.

Scott -- thanks for picking up the "missing link". I was going to move those but forgot to finish. They are still there:
http://home.comcast.net/~ijfritz/demos.htm

Best to all.

Ian
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EdisonRex
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PostPosted: Sat May 05, 2007 2:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

This is the sort of circuit I like to see. Very simple, and very different.

If I may offer my welcome, too, it's wonderful that these forums are attracting good minds. I'm going to have to train my kids better to build circuits. Smile

It's funny, today I am sitting here breadboarding a logic circuit. My intent is to work on a analogue switch logic based "not sequencer" but I'm just sitting here looking at your schematic instead. Talk about derailing a thought. And here I was thinking about randomness.

I think I remember when Electronotes was discussing this. It's been a long time. Your circuit makes more sense and your presentation via the lissajous patterns and the simplified math makes more sense.

How nice.

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frijitz



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PostPosted: Sat May 05, 2007 3:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

Edison -- Thanks for the kind words. As always, Bernie was at the leading edge with this. I watched all the developments in chaos theory go by in the '70s and '80s, but didn't have the time to really learn much about the field.

I finally got the time and have spent the past three years or so clawing my way through several undergraduate-level textbooks and some of the literature on chaos circuits. The breakthroughs for me were realizing that integrators can be used to obtain derivatives and that you don't have to use polynomial nonlinearities obtained with multipliers to make useful circuits.

I have posted some chaos circuits and demos on my website over the past two years, but only temporarily because of lack of space. Now I have more space and am in the process of getting it all back up. Stay tuned if you missed the original posts!

Ian
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EdisonRex
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PostPosted: Sat May 05, 2007 4:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

frijitz wrote:
Edison -- Thanks for the kind words. As always, Bernie was at the leading edge with this. I watched all the developments in chaos theory go by in the '70s and '80s, but didn't have the time to really learn much about the field.

I finally got the time and have spent the past three years or so clawing my way through several undergraduate-level textbooks and some of the literature on chaos circuits. The breakthroughs for me were realizing that integrators can be used to obtain derivatives and that you don't have to use polynomial nonlinearities obtained with multipliers to make useful circuits.

I have posted some chaos circuits and demos on my website over the past two years, but only temporarily because of lack of space. Now I have more space and am in the process of getting it all back up. Stay tuned if you missed the original posts!

Ian


Bernie has always been at the leading edge, despite his insistence on using a Selectric to publish. I don't regret going to WPI instead of Cornell though, although at the time we didn't have anything like the clue they had in New York... I made a few trips up that way but I must confess they weren't always about engineering then... Geek girls were worth traveling for in those days. Smile

I'll be checking your site, but please continue to post here. I'm going through a kind of mid life crisis right now, where I want to build a modular with the parts missing from everything else I have. The problem turns out that I have to revisit all that old math I hated. It's not that scary though, 25 years later.

As mid life crises go, this isn't that bad.

Quote:


I finally got the time and have spent the past three years or so clawing my way through several undergraduate-level textbooks and some of the literature on chaos circuits. The breakthroughs for me were realizing that integrators can be used to obtain derivatives and that you don't have to use polynomial nonlinearities obtained with multipliers to make useful circuits.


This is the part that fascinates me. Do tell, please. You've already simplified a ton of math for me. Your simplicity just illuminates me. Not that I'm gonna be a raving fanboy when I try to build your circuit, but I'm impressed. Smile

I was never a fan of Bernie's complicated math. The reason I didn't end up as a musical engineer was exactly that, the (what turned out to be) over theoretical maths. I went computer science instead. Oh and social science as a dual major, but that's another story.

So please stay and keep explaining. Your site rocks - I groked the whole thing immediately, and I remember not getting the whole thing at all back when it was initially presented. I was a kid then, but at least now I get it, I didn't get it then. I guess there's a reason for a mid life crisis.

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mosc
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PostPosted: Sat May 05, 2007 9:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

welcome Ian, great to have you here.

I was an original subscriber to electronotes. I had a copy of every issue. Then I lent them to someone and I've never seen them again.

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EdisonRex
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PostPosted: Sun May 06, 2007 1:54 am    Post subject: Reply with quote  Mark this post and the followings unread

mosc wrote:
welcome Ian, great to have you here.

I was an original subscriber to electronotes. I had a copy of every issue. Then I lent them to someone and I've never seen them again.


Once again, Howard, we have parallel lives. Laughing Mine were last seen in Potsdam, NY, lent to a faculty member at SUNY Potsdam, now long gone.

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bearblock



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PostPosted: Sun May 06, 2007 6:57 am    Post subject: Reply with quote  Mark this post and the followings unread

this is awesome Very Happy

i have a lorenz attractor in my modular, the circuit by Paul Horowitz that was mentioned. it would be nice for it to have a time-base control for musical applications though - maybe could be done with vactrols? i.e. each opamp would be replaced with one opamp to sum, then the vactrol, then another to integrate... but i'm rambling.

Ian, I will have to get a couple of PCBs in a week or so when i have some more free time. Is 3080 a good OTA for the Jerkster?
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jksuperstar



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PostPosted: Sun May 06, 2007 8:51 am    Post subject: Reply with quote  Mark this post and the followings unread

EdisonRex -- WPI? as in, Worcester Polytech? (I was there from 91-95)
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EdisonRex
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PostPosted: Sun May 06, 2007 9:21 am    Post subject: Reply with quote  Mark this post and the followings unread

jksuperstar wrote:
EdisonRex -- WPI? as in, Worcester Polytech? (I was there from 91-95)


Yes, I was there from 1979 to 1984. The CS department was still in Atwater Kent when I was there and all the big computers were at WACCC in the basement of the library. I was, predictably, active in Lens and Lights, until it got in the way of my studies, and oh did it ever. I did a PQP writing a digital filter (FFTs was the main thing to learn) on a PDP-11. Those were the days, we didn't have enough CPU to do anything real time.

Glad to see another survivor from the Institute. Cool

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frijitz



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PostPosted: Sun May 06, 2007 9:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
This is the part that fascinates me. Do tell, please.


Well, first you understand that an opamp integrator is just an opamp with a cap between the output and (-) input. A constant voltage at the input gives you a ramp at the output. But looking at it the other way around, the input is the derivative (slope) of the output.

So if you have a first order differential equation, then its left hand side is the derivative of a variable, say x', and there is a bunch of stuff on the right hand side which depends on all the variables in the system, say x,y,z.

So you take an integrator and call its output x. Then its input is x', so you simply sum up all the signals that represent the terms on the right hand side of the equation and feed the result into the integrator. Presto, you have a circuit representation of the starting equation.

Then you repeat the above for all the differential equations in the system and you end up with a circuit that couples all the variables together as described by the system of equations, and therefore solves them.

Pretty simple, once you see it!

JC Sprott has looked at using simple circuit nonlinearities to obtain chaos. These nonlinearities I call "kink", the response of a diode and "step", the response of a comparator. Combining these with straight lines gives a variety of useful nonlinear responses. Sprott did exhaustive computer searches for chaos in different systems of equations with these nonlinearities. You can find most of this work on his website:
http://sprott.physics.wisc.edu/technote.htm

So I started out by poaching his ideas and putting them under voltage control, using OTAs to make variable-rate integrators as well as voltage controlled damping and gain. Then I added switches and pots to get different nonlinearities. Oh, and I also hacked an additional signal path with its own nonlinearities. So it's a big complicated system. I used it to get the scarey quadruple scroll attractor on my site and the sound clip that goes with it.

Regarding the double-well system, I was trying to find a simple system that would give lots of interesting outputs, with the idea of giving people something easy to build to get started in this area. So no fancy voltage control and a halfway clever way of combining the nonlinearity, damping and external drive to get the system down to three opamps.

I still have a lot of work to do getting the rest of my experiments up on my site, but I'm hacking away at it bit by bit.

Ian
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frijitz



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PostPosted: Sun May 06, 2007 10:14 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
I was an original subscriber to electronotes. I had a copy of every issue. Then I lent them to someone and I've never seen them again.


Woah! There must have been only a dozen or so original members. I subscribed to EN as a way to catch up on modern electronics. You know, opamps and all that. I had done ham radio stuff earlier, but got away from electronics while in school. It was a real kick for me to eventually get the the level where I could make some contributions.

I don't know if it has been mentioned here, but Bernie is still selling all his material. You can get a package with everything for something like $300. Or you can get a core package, or the Handbook or the circuit collection separately. I still use the Handbook fairly often, since my head doesn't hold all that much.

Ian
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