Fritz chaos circuit

Luka · Joined: Jun 29, 2007 Posts: 1003 Location: Melb.

ian there is a quote in this thread way back on the 2nd page from you which states

frijitz · Posted: Sun Apr 04, 2010 9:13 am Post subject:

macumbista · Posted: Wed Aug 04, 2010 7:09 am Post subject:

macumbista · Posted: Fri Aug 06, 2010 7:15 am Post subject:

macumbista · Posted: Sat Aug 07, 2010 7:17 am Post subject: sound files!

OK, here's two examples of what I've got.

Modules used in these recordings:

Thomas Henry XR-2206 VCO (Bugbrand PCB layout)(VCO range)
Thomas Henry XR-2206 VCO (Bugbrand PCB layout)(LFO range)
Ian Fritz EZ Chaos (Uncle Krunkus stripboard layout)

In the first example, chaos01.mp3, the triangle waveform of the LFO drives the EZ Chaos. The Z (marked NL on schematic) output of the EZ Chaos drives the 1V/Oct input of the VCO. Both Drive and Rate pots are set about at the middle, and the Damping is totally turned down. As you can hear, it maintains a very steady modulation. The changes in modulation pattern only come from my manually adjusting the LFO.

(Incidentally, the X output of the EZ Chaos gave slightly different but still repeating modulations, while the Y output seemed to drive it to the rails.)

In the second example, chaos2.mp3, the poti settings and routing remain the same from chaos1.mp3. However, I have routed the Y output to the Linear FM of the LFO, and the X output to the Exponential FM of the LFO. The modulations become much more chaotic in this setup. Through the clip, I adjust the depth of the LinFM, ExpFM and the general rate of the LFO. Better, don't you think?

So my question is: does chaos1.mp3 sound right, or should I review the circuit again for errors?

Best from Berlin!

chaos01.mp3

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chaos02.mp3

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macumbista · Posted: Sat Aug 07, 2010 1:08 pm Post subject:

Block diagram.....

feedback.png

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andrewF · Posted: Sat Aug 07, 2010 5:52 pm Post subject:

I'm guessing you dont have an oscilloscope handy - the easiest way to observe chaotic behaviour, bit hard to be certain otherwise.
Your samples do sound pretty nuts tho.
The EZ-chaos will not be chaotic at all settings, there are some regions of periodicity.

The Jerkster is the chaos module I seem to use the most, it is very tweakable and goes from mildly batty to chainsaw wielding psychopath in just a nudge of the drive pot. Last month I did an entire performance with only the Jerkster controlling everything, all I did was tweak the Jerkster every now and then, or vary the frequency of the signal driving it.

macumbista · Posted: Sat Aug 07, 2010 7:01 pm Post subject:

Hey Andrew... the non-feedbacked patterns sound to me like a non-linear transfer function, but don't sound chaotic at all in the sense that the transfer function remains almost identical for every cycle of the LFO at any frequency tested.

My understanding of chaotic synthesis comes from the Slater article mentioned in this thread. This involves feedback between at least two--but in my experiments up to 8--cross-modulated VCOs with a non-linear function in the feedback loop. The results tend towards certain attractors, but every cycle is distinct from the previous one, even if after 3 or 7 or 15 cycles later you might return to a common origin.

Assuming that my EZ Chaos circuit functions as it should, the benefit I see out of it would be the ability to make chaotic patterns from a single LFO through the feedback. Normally I would have to use 2 or more LFOs to get the same kind of chaotic oscillations.

However, by itself I don't hear chaos coming from this circuit, only non-linearity. It's the feedback that makes it chaotic for me. Looking at it on the scope is one thing, but hearing it is the proof.

macumbista · Posted: Mon Aug 09, 2010 12:43 pm Post subject:

In case anyone else is curious, the cross-coupling mod as well as some tuning instructions can be found in the manual available for the Elby Designs version of this module:

http://www.elby-designs.com/panther/ed108-chaquo/ed108.htm

frijitz · Posted: Wed Aug 11, 2010 3:58 am Post subject:

wmonk · Posted: Mon Jan 10, 2011 3:57 pm Post subject:

Question about the ChaQuo BOM. It says to use tantalum capacitors for C50 and C51. Is there a specific reason to use tantalum capacitors here? Smile

frijitz · Posted: Mon Jan 10, 2011 8:27 pm Post subject:

RSFC · Joined: Sep 02, 2010 Posts: 63 Location: space lab

I just built a jerkster. Is it supposed to operate in audio range without any CV input? I mean it sounds like it functions I just expected that it was more of a modulation source and put out low fequencies but in my tests so far I find I am using it more as a weird oscillator.

frijitz · Posted: Wed Jan 26, 2011 11:47 am Post subject:

frijitz · Posted: Sun Sep 04, 2011 9:11 pm Post subject: Web page for ChaQuo

ChaQuO now has its own page at my website:
http://home.comcast.net/~ijfritz/projects/ChaQuO.htm
I've included the demos I've posted before on this thread along with a few new ones.

Very Happy

Ian

Dan Lavin · Posted: Mon Sep 05, 2011 2:16 pm Post subject:

I need to put this on facebook so I can "like" it. Thanks Ian! Great selection of samples!

billy pilgrim · Joined: Feb 12, 2008 Posts: 36 Location: nyc

Ian,

I am about to start building the Jerkster and I'm confused by differences between the 2 schematics on your site; the one with the general circuit blocks looks to have the ota inputs inverted compared to the fully fleshed out one. For example the 2 feedback loops return to the inverting input of the 1st OTA on the "general circuit block" version and the non inverting input on the fully fleshed out one. Am I reading it incorrectly ? Any advice greatly appreciated........billy

frijitz · Posted: Thu Sep 08, 2011 7:56 pm Post subject: Re: Jerkster OTA polarity ?

billy pilgrim · Joined: Feb 12, 2008 Posts: 36 Location: nyc

I'll do that, thanks for checking it out.

Sharp eye, Billy. The inputs of all four stages are reversed (it runs OK either way). I have a note that I did that, but I don't remember why. Possibly so that the NL circuit would drive a summing node. I'd recommend using the version on the projects page.

asterisk · Joined: Sep 17, 2011 Posts: 17 Location: burlington, VT

hi,
im building a euro version from ian's double well chaos PCB.

i want to use multiturn pots for the drive and damping so i have some fine control.
im having a hard time finding a 1M multiturn pot for the damping.
would it be okay to just use 100k multiturn pots for both the drive and the damping?

thanks.
*

asterisk · Joined: Sep 17, 2011 Posts: 17 Location: burlington, VT

just confirmed from ian that you can use 100k multi-turn pots for both the damping and the drive pots.

however, since the damping pot is changing from 1M to 100k, you need to change R7 to 470 Ohm.

ill post more when the module is all together with face plate and wiring all done...

asterisk · Joined: Sep 17, 2011 Posts: 17 Location: burlington, VT

so ive just finished up making the Double Well Chaos circuit from the PCB and it doesnt seem to be working correctly.

i was careful with my soldering and wiring and everything but its not working.
the rate pot and the damping pot dont seem to be doing anything at all. the drive pot just a little bit.

ive already done the test settings outlined in the Chaquo manual and elsewhere on the forum and it didnt behave as expected. im not getting any chaotic regions or settings at all. i think the only thing im getting at all is the drive input echoing out the outputs or something like that.

any tips about how to troubleshoot this circuit so i can get it to work?
i dont even know where to start or what problems to look for.

thanks!

andrewF · Posted: Mon Jan 09, 2012 10:27 pm Post subject:

For some settings and types of inputs this circuit doesn't do much. So have a good 1/2 hour trying different input signals and pot settings.

check the op amp power pins are getting the expected voltages. Check everything that goes to ground IS going to ground.

asterisk · Joined: Sep 17, 2011 Posts: 17 Location: burlington, VT

i did your first suggestion with no luck. tried lots of settings for about an hour.
the default setting outlined earlier in this thread and in the chaquo manual and everything in between. not much happening at all.

ill try your other suggestions though. that seems like a good place to start to find out if something isnt soldered correctly or whatever.
there might be a possibility that i forgot to ground one of the jacks. would that mess up the circuit?

v-un-v · Posted: Tue Jan 10, 2012 4:14 am Post subject: