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That looks better. Yes, it might be by putting a variable resistor between R18 & C9 (R34 & C16), such that the maximum compression is fixed. You would have to experiment a bit to find a good value.

R25 and R40 do not really regulate a threshold, but more of an amplification factor: the lower these are, the more the amplifiers around Q5/Q6 and Q10/Q11 respectively, will amplify and the faster the peak detectors will pass the signal to the JFETs. Ofcourse R33 and R51 (attacks) determine how long the signal has to be of high amplitude before the JFETs get to act on it. Ok. so Q1 seems to work as intended.

Not sure which resistor you are referring to with "Sense resistor". Could you please give me the designator Rxx?C3/C4 being 4.7nF should be fine. The filter seems to work since -vlf is indeed only the low-passed signal, ie. high frequencies stripped away. Maybe check that vbuf and collector of Q1 have opposite-phase signals of same size. Also try with separate 100Hz/10kHz signal on the input and see if the signals get split properly before arriving at Q4. Sorry, kinda hard to debug remotely. Good luck!!

Check out this article: https://en.wikipedia.org/wiki/Phase-shift_oscillat...The frequency scales directly as 1/RC.

To the ground of the circuit.

It might be that the input impedance of the USB audio interface is to low, thus loading the circuit to much and quenching the oscillations. You might try a Hi-Z buffer in between the chaos oscillatir and the USB audio interface. A simple non-inverting opamp buffer might help.

Very nice project!So how do they sound, as compared to regular commercial earphones?

Plus sign in circle is the 9V battery plus. Indeed, it is wise to breadboard this first. That will give you the chance to test everything and tweak a little. Good luck!

No, that's what R25 is for. R16 and R17 have to be the same value so to make it that the JFET behaves somewhat as a linear voltage controlled resistor. Get a copy of The Art of Electronics. The JFET-as-a-resistor circuit is well described there.Good Luck!

You're very welcome! Have fun!

Yes, all same-named tags should be connected together. Don't know how experienced you are in building pedals, but I strongly recommend to build, test and tweak-to-your-taste this circuit stage-by-stage on a solderless breadboard first. Good luck!

Ah, yes those 3 tags are just there to name those nodes in the circuit. vbuf should mirror your input signal. vc hf and vc lf are the control signals to the FETs.

Can't! Gave it away.

Thank you! Now build a bunch, hand them out to family and friends, and have a Godot Competition.

Thanks! Yes, or encased in clear polyester resin.

You are absolutely right. Typo. Edited schematic & thanks for capturing that!

While writing a reply to your question, I noticed I made another mistake in copying the circuit from my lab notebook. Extremely sorry for that :-/ (bashes head into keyboard). Edited schematic. So here goes for the explanation:The transistors Q6-Q8 are DC coupled and all in common-emitter configuration (emitters to supply for PNP, to gnd for NPN). DC biasing is provided by R20-R22. Now, imagine the base voltage of Q8 rises a little bit, then its collector voltage and thus Q7's base voltage will decrease. This increases the collector voltage of Q7 and thus the base of Q6. In turn, the collector voltage of Q6 will decrease. Thus the amplifier is inverting. R21 and R22 divide the collector voltage of Q6 by about 3 and feed this back to Q8's base for the biasing. So if the base voltage of Q8 …

While writing a reply to your question, I noticed I made another mistake in copying the circuit from my lab notebook. Extremely sorry for that :-/ (bashes head into keyboard). Edited schematic. So here goes for the explanation:The transistors Q6-Q8 are DC coupled and all in common-emitter configuration (emitters to supply for PNP, to gnd for NPN). DC biasing is provided by R20-R22. Now, imagine the base voltage of Q8 rises a little bit, then its collector voltage and thus Q7's base voltage will decrease. This increases the collector voltage of Q7 and thus the base of Q6. In turn, the collector voltage of Q6 will decrease. Thus the amplifier is inverting. R21 and R22 divide the collector voltage of Q6 by about 3 and feed this back to Q8's base for the biasing. So if the base voltage of Q8 is about 0.6V, expect the collector voltage of Q6 to be around 3x that or 1.8V. This is assuming the drop across R20, who's job it is to isolate C6 from the base of Q8, is zero, which it isn't due to base current of Q8, so DC voltage at the output will be a somewhat higher than 1.8V. C6 together with R21 and R22 form a low pass filter, so no high frequencies get negative feedback, or stated otherwise, high frequencies are not suppressed by negative feedback. Total gain is very high: Collector of Q8 sits at 0.6V below supply. Likewise for Q7 (above ground), so both Q8 and Q7 have around 0.6V/4.7k=0.13mA running through them (ignoring base current of next transistor). This gives a transconductance of gm= 5.2 mA/V (recall you get about 40mA/V of transconductance per mA collector current). This gives Q8 and Q6 an unloaded gain of about 5.2mA/V*4.7kohm = 24, give or take. Similarly, for Q6, assuming 2V across R19, the collector resistor of the last stage, we get a gain of 80. Total gain of the 3 stages, should they not load each other, would be a whopping 24*24*80> 46000, for in total 0.63mA of supply current (measured at 4V supply). However the stages load each other a bit, so total gain is going to be lower, but still enough to pick up all kinds of noise from the environment, using a short open lead antenna.The oscilloscope screenshot shows the collector voltage of Q6 at 4V supply.Now hope I didn't make any errors here! :-/ Cheers!

Thanks! Curious now: which problems?

So funny!! Bravo!

This is beyond beautiful!!!

Thanks!!

Cool project and looks really neat! Did you notice any improvement in air quality. I guess I want to ask: how well does it work?

Thanks! Liked your Solar System Spiral Earrings! :-)

Hi Frederico,Thanks!Indeed, that's a typo, should read Q7 and Q8.Unfortunately no BOM, since I drew this right away in Xfig.One word of advice: build it on a breadboard first, so you can adjust the component values to your liking. The JFETs characteristics make quite a difference, so you might want to tune a little.Good Luck!

Hi Frederico,Thanks!Indeed, that's a typo, should read Q7 and Q8.Unfortunately no BOM, since I drew this right away in Xfig.One word of advice: build it on a breadboard first, so you can adjust the component values to your liking. The JFETs characteristics make quite a difference, so you might want to tune a little.Good Luck!

Hi Frederico, Thanks!Indeed, that's a typo, should read Q7 and Q8. Unfortunately no BOM, since I drew this right away in Xfig.One word of advice: build it on a breadboard first, so you can adjust the component values to your liking. The JFETs characteristics make quite a difference, so you might want to tune a little.Good Luck!

Hi Frederico,Thanks!Indeed, that's a typo, should read Q7 and Q8.Unfortunately no BOM, since I drew this right away in Xfig.One word of advice: build it on a breadboard first, so you can adjust the component values to your liking. The JFETs characteristics make quite a difference, so you might want to tune a little.Good Luck!

Hah! You found a typo! During breadboarding I used 100k and later went to 50k, because the increased resistance messes a bit with the DC setting at the emitter of Q2, due to base current. Just use a dual 50k but breadboard first, you might want to adjust C3 and C4 or other values here and there. Good luck & thanks!

I tried out different models of BC547C, as these differ somewhat per manufacturer. The one I settled for was that model that came the closest to the experimental outcome. Note in the code in my previous post, only one model is actually used.IC stands for initial condition, here initial voltage on the capacitors at t=0. This code was part of a loop to build a bifurcation plot. For each itteration of the loop, a resistor value was stepped and the simulation repeated, taking of in the state (capacitor voltages) in which the previous one ended.

Thanks. It should work right out of the box. This is my simulation code that works with ngspice:*** RC Chaos Generator **** Supply vcc 1 0 5.0V* CircuitR1 1 2 5kR2 4 7 15kR3 2 6 30kR4 6 0 47kR6 2 3 5kR7 3 4 10kR8 4 5 10kC1 3 0 1nF ic=1.290847C3 4 0 1nF ic=0.676498C4 5 0 1nF ic=0.645246C2 6 0 360pF ic=0.607691Q1 2 5 0 BC547CV2Q2 7 6 0 BC547CV2.model BC547C NPN(Is=32f Xti=3 Eg=1.11 Vaf=100 Bf=720+ Xtb=1.5 Br=6.313 Isc=138f Nc=2.053 Rb=1.3k+ Ikf=500m Ise=230f Ne=1.583 Nk=1.05+ Ikr=.187 Rc=.4216 Cjc=5.25p Mjc=.3147 Vjc=.5697 Fc=.5 Cje=11.5p+ Mje=.3333 Vje=.5 Tr=10n Tf=410.7p Itf=2.204 Xtf=66.65 Vtf=10).model BC547CV2 NPN(Is=7.049f Xti=3 Eg=1.11 Vaf=24.76 Bf=543.1 Ise=78.17f+ Ne=1.679 Ikf=94.96m Nk=.5381 Xtb=1.5 Br=1 Isc=27.51f Nc=1.775+ Ikr=3.321 Rc=.9706 Cjc=5.25p Mjc=.3147 Vjc=.5697 Fc=.…

Thanks. It should work right out of the box. This is my simulation code that works with ngspice:*** RC Chaos Generator **** Supply vcc 1 0 5.0V* CircuitR1 1 2 5kR2 4 7 15kR3 2 6 30kR4 6 0 47kR6 2 3 5kR7 3 4 10kR8 4 5 10kC1 3 0 1nF ic=1.290847C3 4 0 1nF ic=0.676498C4 5 0 1nF ic=0.645246C2 6 0 360pF ic=0.607691Q1 2 5 0 BC547CV2Q2 7 6 0 BC547CV2.model BC547C NPN(Is=32f Xti=3 Eg=1.11 Vaf=100 Bf=720+ Xtb=1.5 Br=6.313 Isc=138f Nc=2.053 Rb=1.3k+ Ikf=500m Ise=230f Ne=1.583 Nk=1.05+ Ikr=.187 Rc=.4216 Cjc=5.25p Mjc=.3147 Vjc=.5697 Fc=.5 Cje=11.5p+ Mje=.3333 Vje=.5 Tr=10n Tf=410.7p Itf=2.204 Xtf=66.65 Vtf=10).model BC547CV2 NPN(Is=7.049f Xti=3 Eg=1.11 Vaf=24.76 Bf=543.1 Ise=78.17f+ Ne=1.679 Ikf=94.96m Nk=.5381 Xtb=1.5 Br=1 Isc=27.51f Nc=1.775+ Ikr=3.321 Rc=.9706 Cjc=5.25p Mjc=.3147 Vjc=.5697 Fc=.5+ Cje=11.5p Mje=.6715 Vje=.5 Tr=10n Tf=410.7p Itf=1.12 Xtf=26.19+ Vtf=10)* PHILIPS pid=bc547c case=TO92* 91-07-31 dsq* Simulations.controltran 100ns 5mswrdata out v(2) v(3) v(4) v(5) v(6)exit.endc.endPlotting column 2 and 4 of the resulting out.data using Gnuplot results in below image.Please post an "I made it" if you get it working. Good luck!

Thanks! Will post some recordings soon. Just have to set up the stuff to record here...

Indeed there was. Somehow a part of the text got disapeared.Thanks for catching that!

Cool! Planning on making an ebook reader cover following your method!