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frijitz
Joined: May 04, 2007 Posts: 1734 Location: NM USA
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loss1234
Joined: Jul 24, 2007 Posts: 1536 Location: nyc
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Posted: Thu Nov 29, 2007 9:36 pm Post subject:
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so you did nothing to the circuit except change to a 12v supply?
I have been interested in non-linearity for a long time and I see that you have mentioned many times that diodes have non-linear properties. So is it possibe to add chaotic elements to circuits by replacing resistors with diodes? Or do you really need to approach this from a math standpoint?
I ask because I am wondering if there are ways to take MORE pre-existing circuits and push them toward chaos.
thanks for all your work into chaos circuits. I only hope my skills catch up to my interest in this field. _________________ -------------------------------------------- check out various dan music at: http://www.myspace.com/lossnyc
http://www.myspace.com/snazelle
http://www.soundclick.com/lossnyc.htm http://www.indie911.com/dan-snazelle |
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Tim Escobedo
Joined: Nov 27, 2007 Posts: 3 Location: California
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Posted: Thu Nov 29, 2007 9:42 pm Post subject:
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Wow. That's a pretty neat bug/feature. I can't even begin to account for that behavior. If only I knew about it earlier.
I'm curious. What kind of op amps are you using? I almost universally use plain low powered TL06x chips. Occasionally TL07x series. I noticed the SK quad filters were 5534 I think. I have in the past treated op amps rather generically. |
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frijitz
Joined: May 04, 2007 Posts: 1734 Location: NM USA
Audio files: 54
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Posted: Fri Nov 30, 2007 8:42 am Post subject:
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loss1234 wrote: | so you did nothing to the circuit except change to a 12v supply?
So is it possibe to add chaotic elements to circuits by replacing resistors with diodes? Or do you really need to approach this from a math standpoint? |
No significant changes. The feedback network is the same, except for 450p instead of 500p for the small cap. (A larger cap actually gives a more dramatic chaotic behavior.) The CV input is not connected. The freq control has a bypass cap, but it doesn't make any difference. The bypass cap at the Vcc/2 supply is left off, but that doesn't make any difference either. The audio coupling cap is 0.1 instead of 0.01.
In general, chaos only occurs under special conditions, so just throwing some nonlinear element into a circuit usually doesn't result in anything interesting. That's why I was so surprised to see chaos in this circuit. Most of the work I have done with chaos is based on systems that have been studied previously.
Ian |
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frijitz
Joined: May 04, 2007 Posts: 1734 Location: NM USA
Audio files: 54
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Posted: Fri Nov 30, 2007 8:53 am Post subject:
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Tim Escobedo wrote: | Wow. That's a pretty neat bug/feature. I can't even begin to account for that behavior. If only I knew about it earlier.
I'm curious. What kind of op amps are you using? I almost universally use plain low powered TL06x chips. Occasionally TL07x series. I noticed the SK quad filters were 5534 I think. I have in the past treated op amps rather generically. |
Yeah, i didn't expect the chaos at all. At first I thought I was just having trouble with my scope triggering. But triggering off the input signal straightened me out on that.
I used an LF351 (similar to TL071). I also threw in an older slow opamp (BB3500, similar to LM307), but other than the slower slew rate it worked the same. So I don't think there is any major contribution from an opamp pole or anything weird like that.
The signal is different from anything I have seen before. As the input signal crosses zero from below, the opamp slews very rapidly upward, usually clipping. Then the decay of the waveform is much slower. So the opamp clippping may be an important part of the systems nonlinearity. Not sure about that at this point.
Ian |
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frijitz
Joined: May 04, 2007 Posts: 1734 Location: NM USA
Audio files: 54
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Posted: Fri Nov 30, 2007 7:05 pm Post subject:
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I've looked at this interesting circcuit a bit more. After reducing the input drive to +/-50 mV there is still nonlinear behavior. As the driving frequency is increased there is a resonance when f = f0 (the main resonant frequency) then around f = 2f0 the period of the output signal doubles and there is another resonance at f = 2f0. So the resonance occurs twice at the same output frequency but for input frequencies of f0 and 2f0. I'm surprised nobody has noticed this before. I have checked all the wiring and the component values very carefully. Well, perhaps it's the larger supply voltage.
Ian |
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frijitz
Joined: May 04, 2007 Posts: 1734 Location: NM USA
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loss1234
Joined: Jul 24, 2007 Posts: 1536 Location: nyc
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StephenGiles
Joined: Apr 17, 2006 Posts: 507 Location: England
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Posted: Sat Dec 01, 2007 4:20 pm Post subject:
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Our dog was quite alarmed at the noise! |
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gmeredith
Joined: Jun 28, 2006 Posts: 82 Location: Tasmania, Australia
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Posted: Sun Dec 02, 2007 9:58 pm Post subject:
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Hi Frijitz,
You seem to really be developing something here! If you can figure out just what makes the chaos, it would make a great bend for the Casio SK Phat Philter he he
Did you build the filter straight from Tim's schematics, or from my Phat Philter plans? I'm trying to find out what the difference must be. What op-amp are you using?
I did come across an anomality while designing the board. I found that a TL071 op-amp has a dead zone when you turn the cutoff 100K pot below, say, 1 quarter. it just seemed to mute. Other op-amps didn't show this behaviour.
I had the input attenuated a fair bit for line level input, so I didn't have it overloaded to see what it would have done otherwise. Interesting.
Cheers, Graham |
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frijitz
Joined: May 04, 2007 Posts: 1734 Location: NM USA
Audio files: 54
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Posted: Sun Dec 02, 2007 10:31 pm Post subject:
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Graham -- As discussed some above, I have looked at a number of variations of the circuit, including different opamps and supply voltages. I RE'ed your layout, and it seems to me basically the same circuit as the original. There is no chaotic behavior when the diode is replaced by a resistor. So the diode is actually doing two things, I believe: (1) it acts as a tunable resistance in the twin-T network (as intended) and (2) it acts as a nonlinear circuit element, thereby inducing the chaotic behavior. It would take some fairly tedious numerical analysis to show that the chaos is expected, but it really doesn't seem all that improbable (in hindsight!). If you have the means, you might try driving it a bit harder to see what happens in your setup.
Ian |
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loss1234
Joined: Jul 24, 2007 Posts: 1536 Location: nyc
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Posted: Thu May 08, 2008 10:23 am Post subject:
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ian
i have been building this circuit and I wanted to know if you bothered using the VR bias (when you used a 12v supply)
in other words, on tims original schematic he shows a SINGLE supply being split in half and then fed into the 1m vr resistor going into the +input. did you emulate this with 12v or just skip it and use bipolar?
one thing i noticed (and most likely why tim included the trimmer) is that the circuit distorts very easily, and not in a very pretty way either. is this the key? just overdriving that input? i can tell already that this has a much stranger response than my other filters.
thanks
(scope is coming this week!) _________________ -------------------------------------------- check out various dan music at: http://www.myspace.com/lossnyc
http://www.myspace.com/snazelle
http://www.soundclick.com/lossnyc.htm http://www.indie911.com/dan-snazelle |
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frijitz
Joined: May 04, 2007 Posts: 1734 Location: NM USA
Audio files: 54
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Posted: Thu May 08, 2008 12:55 pm Post subject:
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loss1234 wrote: | i have been building this circuit and I wanted to know if you bothered using the VR bias (when you used a 12v supply)
in other words, on tims original schematic he shows a SINGLE supply being split in half and then fed into the 1m vr resistor going into the +input. did you emulate this with 12v or just skip it and use bipolar? |
Both. I used 0/12V (and 0/9V) with the split, and I used +/-12V without it.
I dropped working on this, as the Threeler was much more interesting.
Ian |
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loss1234
Joined: Jul 24, 2007 Posts: 1536 Location: nyc
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Mikmo
Joined: Dec 01, 2005 Posts: 150 Location: Copenhagen - Denmark
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Posted: Thu Sep 04, 2008 12:44 pm Post subject:
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Sorry to revive an old thread, but did anybody design a PCB for this filter?
If so i would really like to see / buy it.
Thanks
Mikael _________________ Stay Cool
Mikael
http://www.mikmo.dk |
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fonik
Joined: Jun 07, 2006 Posts: 3950 Location: Germany
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Posted: Fri Sep 12, 2008 5:37 am Post subject:
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frijitz wrote: | Both. I used 0/12V (and 0/9V) with the split, and I used +/-12V without it |
i have to confess: i don't get it from the schematic
if i use the split i get a virtual ground labeled Vx, right? where does this apply to the circuit? what does Vr mean? why is the attenuator wired to the ground symbol when i split the supply?
i would have expected the following:
using the split, the attenuating pots are wired to virtual ground Vx. same applies to the 1M resistors at the positive OpAmp inputs. freq control potentiometer goes from +V to ground (actual the virtual -V)...
maybe i am a little bit dumb, but i don't understand the schematic here, so any explanation is appreciated. _________________
cheers,
matthias
____________
Big Boss at fonitronik
Tech Buddy at Random*Source |
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Uncle Krunkus
Moderator
Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
Audio files: 52
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Posted: Fri Sep 12, 2008 5:47 am Post subject:
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Where is the schem? _________________ What makes a space ours, is what we put there, and what we do there. |
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jnuaury
Joined: Feb 28, 2008 Posts: 161 Location: chicago
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frijitz
Joined: May 04, 2007 Posts: 1734 Location: NM USA
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Posted: Fri Sep 12, 2008 7:36 am Post subject:
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fonik wrote: | frijitz wrote: | Both. I used 0/12V (and 0/9V) with the split, and I used +/-12V without it |
i have to confess: i don't get it from the schematic
if i use the split i get a virtual ground labeled Vx, right? where does this apply to the circuit? what does Vr mean? |
I don't see any Vx on the schematic. It's an odd circuit, but it goes chaotic under a variety of conditions.
Ian |
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fonik
Joined: Jun 07, 2006 Posts: 3950 Location: Germany
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Posted: Fri Sep 12, 2008 11:33 am Post subject:
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right. i misread the Vr in the split circuit for Vx, due the serife font
however, i would have expected the attenuating potentiometer on the audio input to go to Vr then. isn't Vr the virtual ground here? _________________
cheers,
matthias
____________
Big Boss at fonitronik
Tech Buddy at Random*Source |
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frijitz
Joined: May 04, 2007 Posts: 1734 Location: NM USA
Audio files: 54
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Posted: Fri Sep 12, 2008 1:03 pm Post subject:
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fonik wrote: | however, i would have expected the attenuating potentiometer on the audio input to go to Vr then. isn't Vr the virtual ground here? |
Right. That's just how Tim's circuit is. The circuits I did with unipolar and bipolar supplies were not equivalent to each other. But both showed chaos. Whiteboard it up and try it!
Ian |
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fonik
Joined: Jun 07, 2006 Posts: 3950 Location: Germany
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Posted: Fri Sep 12, 2008 4:23 pm Post subject:
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frijitz wrote: | fonik wrote: | however, i would have expected the attenuating potentiometer on the audio input to go to Vr then. isn't Vr the virtual ground here? |
Right. That's just how Tim's circuit is. The circuits I did with unipolar and bipolar supplies were not equivalent to each other. But both showed chaos. Whiteboard it up and try it!
Ian |
thank you ian. i will do that. again you gave me some good answers today (as always) - thank you very much. _________________
cheers,
matthias
____________
Big Boss at fonitronik
Tech Buddy at Random*Source |
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alcofribas
Joined: Oct 03, 2008 Posts: 22 Location: Eastern France
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Posted: Sat Nov 07, 2009 5:49 am Post subject:
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Geocities has been dead for a while now, can somebody post that mysterious schematic again?
Thnx
Alcofribas |
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andrewF
Joined: Dec 29, 2006 Posts: 1176 Location: australia
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crochambeau
Joined: May 18, 2008 Posts: 31 Location: earth.
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