Synthesizer Build part-61: TRIPLE SLOTHS chaotic voltage sources.

The triple sloths by Nonlinearcircuits is a chaotic modulation source. It has 11 outputs that produce slowly changing voltages that follow a chaotic path. Great for generative patches and ambient music.

The module will fit in a Eurorack Nifty Case. I also made a layout for Kosmo sized modules.

This is a module I wanted to build for a long time and I finally got 'round to building it. This module produces random control voltages. We have 3 boards, Torpor, Apathy and Inertia. Torpor has the fastest changing voltages. It takes about 15 to 30 seconds to travel around 2 strange attractors, if you watch the plot on an oscilloscope set to X-Y display. Apathy takes about 60 to 90 seconds and Inertia takes about 30 to 40 minutes. Sloths cycles but it never repeats itself! It evolves.

Torpor and Apathy both have a potmeter. The potmeter doesn't change the frequency as you would expect but it changes the tendency of the waveform to be attracted to one or the other attractor. It nudges the waveform in a different direction you might say, that's why I labelled the potmeters 'Nudge'.

Inertia doesn't have a potmeter or a CV input. It just does it's own thing.

Torpor and Apathy have CV inputs, Most of the time a CV input signal will be added on top of the output signals of the module but it can also have the effect of changing the path of the voltages.

You can use an output from one stage to input into an other stage to get even weirder voltage paths.

We have an X, Y and Z output for each stage. Each of these outputs are taken from a different part of the circuit and the Z output is simply the inverted version of the Y output. The two extra Z outputs at the bottom are made up like this: V (Z3+) = Vz Apathy + Vz Inertia - Vz Torpor if greater than 0 otherwise it's 0V.

V (Z3-) = Vz Apathy + Vz Inertia - Vz Torpor if smaller than 0 otherwise it's 0V.

Beware that the voltages summed together can add up to + or -10V so attenuation on those signals would be a good idea.

The X outputs are the lowest in voltage. They stay between +/- 2.5Volt. It will cycle around the 0V line.

The Y outputs vary around +/- 5Volt. They will stay positive for a while and then go negative for a while.

The Z outputs are the same as the Y outputs only inverted.

With testing the Sloths on one board, I found the X output voltages of the Apathy and Inertia circuit much higher than +/- 2V. So I tried putting in voltage dividers but when I then mounted the board behind a panel the X voltages were suddenly too low. Really puzzling. 

I ended up taking out the 1K resistors to the X outputs of the two problematic circuits and putting in 10K trimmers on the copper side. That solved the problem because I can now dial in the voltages from the X outputs. I connected pin 1 of the trimmer to pin 1 of the TL074 (the signal source). The wiper of the trimpot went to the X output strip and pin 3 of the trimmer went to ground which is the strip below the output. See picture below.:

LAYOUTS:

Below are the layouts I made for this module. As always they are verified. I used them to build my module. We have a stripboard for each of the three stages and one for the extra two Z-3 outputs that mix the Z outputs from all 3 modules together.

Here is the overall layout showing all boards (Kosmo size layout further down). 

[EDIT] on Nov. 6th 2024 I made a slight alteration to the layouts. I routed the LED output through the left over opamp so that is doesn't pull down the voltage of the Z output.

There's not much room for the 1µF capacitors but it doesn't matter if the underside of the caps stick out above the resistors a bit as long as the leads are not touching other components. I put in higher value resistors as current limiters for the LEDs because the 470Ω ones recommended in the schematic made the LEDs shine awfully bright. I thought 1K8 would be better, and they are. All non inverting inputs (+) of the opamps in the TL074 are grounded so the strips that connect pin 3 to 12 and pin 5 to 10 must not be cut underneath the chip.

Here's the Torpor board:

Here's the Apathy board:

Here's the Inertia board:

And finally the extra Z outputs board:

You tap the Z inputs from the Z-outputs of the three boards.

I didn't make any layouts with just the cuts and wirebridges because these are such small boards that you can easily see where the cuts need to be made and where to put the wirebridges.

Do be aware that the Apathy board has an extra cut in it above the TL074 chip. All boards differ from eachother slightly so do pay close attention when working on them.

Here is the Bill of Materials. There are some very high value resistors needed for the Inertia board and I used Bi-polar capacitors on all boards so you need to order these new instead of putting them together by putting capacitors in parallel. I did leave room to do that at the top of the stripboards but it's easier to just order Bi-polar caps. I did have to make my own 100M resistor by putting ten 10M resistors in series and I used three 33M resistors in series to make the 68M resistor. My local electronics store didn't have them. I only had the 2 Watt versions of those so they took up a lot of space. I should have just used six 10M resistors in series for that one too. For the 1µF caps I ordered ten 1µF WIMA MKS box capacitors with 5mm distance between the legs. They are not polarized and work very well here although they are a bit bigger than round 1µF bi-polar caps, but it fitted well enough.

KOSMO SIZE LAYOUT:

Here's a layout I made later just in case you want to build this for a Kosmo sized setup. In that case you can have all three Sloths on one piece of stripboard and it gives you a little more space to place the capacitors too. Again I made a slight alteration to the previous version in that the LED output is now routed through the left-over opamp so it is buffered and can't pull down the Z output voltage.

This layout is also verified. I've just finished building this version too.

Use the extra Z outputs board posted above to add to this main board.

Sloths one board with extra Z outputs board. Cuts and wirebridges.

SCHEMATIC:

Because this is a kit that Nonlinearcircuits is selling to create income, I'm not going to post the schematic here. Instead I'm going to link to it on the Nonlinearcircuits website, because I don't want to negatively impact their revenue.

The link opens the Triple Sloths page and if you scroll down you'll find a green button marked 'build instructions' and if you click that you can download the PDF which also has the schematic in it.

--- CLICK HERE ---

If you do not want to build it on stripboard you can order the complete kit from nonlinearcircuits instead, with PCB's. That module will be 8hp wide. The one I made is 14hp wide because I needed more space to put three stripboards vertically behind the panel. The kit does require you to solder SMD parts unless you get a singel 4hp Sloth module which is through hole.

You can have a look at the schematic for the Torpor circuit in this Falstad simulation I made:

--- CLICK HERE ---

DIY BI-POLAR CAPACITORS.

If you are having trouble finding bi-polar capacitors, you can make your own. Below here is the schematic for a bi-polar cap made up of polarized capacitors.

The equivalent value of a cap made like this is the same as the value of one of the polarized capacitors, provided you use two caps of the same value. So for instance if C1 is 100µF and C2 is 100µF then the equivalent value of the bi-polar capacitor you created will also be 100µF because each of the two caps is used for one phase of the signal. One for the positive side and one for the negative side.

It might be a good idea to use Schottky diodes for D1 and D2 because of their lower voltage drop and I can not guarantee this method actually works. I just thought I'd mention the option but I haven't tried it myself.

 

Bi-polar capacitors are used a lot in audio speaker cross-over filters, so that is one place where you can start looking if you want to buy them new. I tried to Google them and had no problem finding them online. Just use the search terms: bi-polar, bipolair or audio capacitors.

OSCILLOSCOPE SCREENSHOTS:

Below are some screenshots I took during testing. You can see the random voltages at work. Yellow is X and blue is Y. You can see that Y has a higher voltage than X. The last one shows what happened when I put a triangle wave on the CV input of the Torpor module. The signal was added on top of the voltage. The first three screenshots below were are from the Eurorack version with the separate boards.

Here are some screenshot I took when testing the Kosmo sized stripboard with all three Sloths on one board. These are taken from the X outputs of the three boards.

This is over a timespan of 2 minutes. Yellow is Torpor, blue is Apathy and purple is Inertia. You can see the voltages are not all within +/-2V so I experimented with putting in voltage dividers but that didn't work out well.

This one is the same as the one above only with a timespan of 4 minutes.

Again you can see here that the voltage of the Apathy and Inertia X outputs is much higher than the Torpor X output. I don't know why this is the case because I checked and double checked. I switched IC's etc. but I couldn't find anything wrong.

Here's a series of three screenshots with the X,Y and Z outputs of each circuit after I put in the voltage dividers but before the board was mounted behind a panel. Here's the Torpor:

Apathy X,Y & Z:

Inertia X,Y & Z:

You may notice that there's not much difference over time in the waveforms, especially the last two but that occurs over time and in very small amounts. Try experimenting with feeding slow LFO signals into the CV inputs of Torpor and Inertia. You can use one output of Sloths to go into the CV input of another Sloths.

Z3 plus output:

Z3 minus output:

PICTURES:

Here are some pictures I took when building the Kosmo version:

I made the 100M and 68M from 10M resistors in series. I put small pieces of heatshrink tubing on the soldered ends where the resistors connect to eachother to prevent accidental short circuits. Then I hotglued the resistors in place. 

I didn't have a 39µF bipolar cap so I put in a 22µF (in the Inertia part) and added two polarized 10µF caps with diodes attached like I showed earlier in the article. I'm not sure if it has an influence. The capacity meter doesn't pick up the extra capacity because of the diodes but at least it is working normally.

With the 100M resistor made up of ten 10M resistors in series I added a center tap point that I connected to a copper strip that was not in use. I wanted to add a switch so I could half the resistance to make the Inertia part of the circuit work a little faster if I wanted to. That didn't work out though. It did go faster after closing the switch but the output voltage also shot up way too high. So do not replicate my experiment.

Here you can see how I mounted the Z outputs board. It is just floating. The main Sloths board is mounted by putting two sets of copperwire through the ground strip at the top and twisting and soldering them together and then soldering them to the ground connection wire or the sockets. The socket grounds are all connected together with one copper wire going through all the ground lugs of the sockets.

Here's a look at the finished panel mounted in the synth:

Below are some pictures from building the Eurorack version.

Here you can see the 'Inertia' board with the 100M resistor I had to make from ten 10M resistors in series. I made the 68M from three 22M resistors. These were big 2 Watt resistors. In hindsight it would have been better to have used six 10M ¼ Watt resistors in series.

Here are the three boards together. I soldered powercables to them for testing. When they were mounted behind the panel each board got power from the board beside it with simple daisy chained wire connections. You could use pinheaders but you'll need the extra high version.

One thing I noticed when testing, which is important to know, is this: I connected the Torpor module to my bench powersupply and it would only produce sinewaves but they weren't random. This turned out to be a fault in my powersupply. When I connected it to my synthesizer powersupply it worked normally.

Here you can see the backside of the module. Three boards tucked in together with the extra Z outputs underneath. The two outer boards are connected to the faceplate through the potmeter that is soldered straight to the stripboards. The Inertia board has no potmeter and it is mounted inbetween the two others and secured with hot glue.

Wiring these stripboards up was very time consuming. It took me almost a whole day. Because there is almost no access after the boards are mounted behind the panel, you have to solder the wires to the boards first. Put in all the sockets and ground them all. Then put in the boards and solder the wires to the sockets. To save space I soldered three wires to a Female Eurorack powerconnector and soldered the wires to the Torpor board. The other three boards get their power from the board to the left of it with again three wires. Be careful that non of the components touch the copper strips of the neighbouring boards. I put in gaffa tape and hot glue to protect some areas from short circuits.

Here's the finished module with the faceplate made with the waterslide paper method. Again I made a mistake. I forgot the two CV inputs. Well, there was room enough to put them in they are just not labeled. I called my module Sloth, not Sloths for no reason really :-D

Btw, these knobs are temporary. The ones I'm going to use are slightly larger but they are still in the mail.

When you start designing your panel layout make sure to offset the sockets a little from the potmeter positions. Don't put them straight underneath the potmeters because the stripboards will touch them. Put them slightly to the left. I did make that mistake and I had problems getting the boards to fit. 

And like I said before, don't forget to put in the CV inputs. ^_____^

DEMO VIDEO:

First a little demo I filmed myself with the following patch: Sloths Torpor X output goes into the 2hp Tune quantizer which turns the voltage into random notes following a chromatic scale then the 1V/Oct signal from the 2hp goes into the Digisound 80 VCO and from there into a 2164 Lowpass filter which has the cutoff controlled by Sloths Torpor Y output. Although that didn't come out very pronounced.

Here's a little demo of the Kosmo sized Sloths in action with the Torpor and Apathy X outputs controlling the filter cutoff of the TH State Variable Filter and the Lowpass Gate.

Here's a cool video I found on YouTube explaining how this module works:

TIP: lead the output of one of the sloths (the faster one like Torpor Y output) into the signal in of a Sample and Hold to get random stepped voltages like the Turning Machine produces.

Okay that's another one done.

If you have any comments or questions about this module then please put them in the comments below or in the special Facebook group for this website. Beware that comments are moderated and don't appear until I approved them.

Synthesizer Build part-34: TRIPLE WAVEFOLDER.

A wavefolder with three folding stages which produces amazing sounds and it's very easy to build too!

I came across this project on YouTube when I watched a video by YouTuber Adamski A. called "DIY analog synth project part 18 - The Wavefolder".

So I set about building it and it came out very well so I asked Adam for permission to write an article for my website, based on his project, to which he very enthusiastically replied in the affirmative so here it is; The Triple Wavefolder.
Like I said, it's a very simple design and in my experience those work the best. This wavefolder produces sounds that I would describe as sharp or hard and accurate. In some settings it almost resembles a Harpsichord or an electric piano. They can be real speaker rippers too. If you watch Adam's video (see link above) you can listen to the wavefolder in action. The latter part of the video is full of sound samples in different settings. I also made a little demo video myself which is at the bottom of this article. The sound is very different from that of the filters we've become so used to, with their resonance and cut-off frequency. It sometimes almost sounds like an FM synthesizer. That's why this is a very useful addition to any modular set-up because diversity in sound is what we all want don't we?
Now, I built the Yusynth Wavefolder after first building this because I thought that this triple wavefolder was more of an experimental thing and the Yusynth one would be the official implementation to go into my synthesizer. But the Yusynth one only has a single folding stage and eventhough that sounds amazing too, I found that this one actually sounded even better. So I made a panel for it and mounted it in my synthesizer. The voltage it runs on has an influence on the number of folds you can get so changing the value of the 22K resistors going to the emitters of the transistors influences the behaviour of this circuit.

This wavefolder works best with Triangle or Sawtooth waves or even Sinewaves but Squarewaves pass through almost unchanged. That's convenient because squarewaves are best used for conventional filters because of their harmonic content.

Adding CV control to the parameters:
This wavefolder has in it's original form only three controls; the input level or 'Amount', the Dry/Wet control and a Saturation control. As an experiment I added voltage control to two of those, the Amount and Saturation by means of two self-made Vactrols connected between pins 2 and 3 of the respective potmeters.
These vactrols are made up of a bright white LED, a Light Dependent Resistor (LDR) and a 2K2 current limiting resistor connected together with some heat-shrink tubing that seals it off from any light from the outside.
These Vactrols both have their own level potmeter too so you can dial in the effect it has very accurately. I've had questions about what LDR's you should order for these and I really can't tell you. I had mine in stock for ages. A while back I ordered a batch of 5 x 10 LDR's from China. 5 different values with 10 of each value. They all have a dark-resistance of at least 100 Mega Ohm and a full light resistance around 1 Kilo Ohm or lower. That's all I can say. You can also buy Vactrols ready made like the VTL5C3 which should work fine here.

Even better than a Vactrol, at least for the Amount parameter, is to use a VCA on the Wavefolder input, That way you can control the level and thus the Amount by sending a Control Voltage into the VCA. This works much better and it's what Adam also demonstrates in his video. (See the 'Metalizer' project elsewhere on this website. That is in principle a quadruple wavefolder with a VCA on the input.)

In the video demonstration the vactrols didn't have that much effect but I had forgotten that the potmeters for Amount and Saturation need to be set a good way counterclockwise for the Vactrols to take full effect. And in that sense you could in principle do away with the CV Level potmeters because the Amount and Saturation potmeters have that function too for Control Voltages. But you must not forget that this module was built first and foremost as an experiment that I didn't think I would publish. 

Anyway, you could decided to leave the CV inputs out alltogether, it's up to you.

THE GAIN CONTROL:
The other thing I addressed was the fact that the Amount control is also the Amplitude or Volume control so turning it up increases the volume and turning it down decreases it. For that reason I added a Gain potmeter to the output opamp which increases the volume by a factor of 2 to 22 times!! This option is a game changer for this wavefolder especially with this much Gain! This gives you the possibility to really boost the sound output and it sounds awesome I can tell you. You can really boost the lower and mid ranges of the Amount potmeter to match the high output level when Amount is fully open. I even found that opening up the gain helps to level out the output amplitude across most of the Amount potmeter throw without really clipping the output. But even if it does clip, it adds a very musical sort of distortion to the sound. It's never unpleasant to listen to.

Here's the schematic drawing of the Triple Wavefolder by Adamski A. I have re-drawn it and added the Vactrols to it. I mention on the schematic that you can also use BC transistors instead of the 2N transistors I used, but that will influence the sound or the number of folds you get because BC transistors have a greater multiplication factor. You can of course experiment with that by setting up the circuit on a breadboard first. (Btw, the BC548 and BC558 can also be BC547 and BC557 types.) The CV-Level control potmeters are not included in the schematic. This is because I added the CV control as a bit of an after-thought to see how it would work out. Like I mentioned before you don't have to include the Vactrols and CV level controls. I leave that up to you.

(Last revised: 11-July-2020: Changed GAIN potmeter from 20K to 100K.)

Here's the stripboard layout. It's verified because I used this for my own build. All potmeters are viewed from the front side with shaft facing you!
(Wiring diagram):

(Last revised: 11-July-2020: Changed GAIN potmeter from 20K to 100K.)

Print only. Note that pins 5 and 10 of the TL084 are connected underneath the chip!!:

Bill of Materials.

15V vs 12V and de-coupling:
As you can see a very simple and easy to build project and it sounds amazing so I can really recommend trying this one out. The circuit is meant to work on a dual 15V powersupply but I tested it on 12V and it works just fine but changing the voltage does influence the number of folds you get so it sounds a bit different but it still works fine, trust me =)
I did not include any de-coupling capacitors in the schematic because I didn't use any but if you need to have those included just put a 100nF from plus to ground and a 100nF from ground to minus and place them as near to the TL chip as possible. Should you have problems with hum, you can also add a few electrolithic caps (22µF or 33µF) on the plus and minus rails like the other caps and you can also try putting Ferrite Beads in series with the plus and minus power supply input, or if you don't have them, a few 10 Ohm resistors. There's plenty of room on the stripboard for that. But you only need to do that if you're having problems with hum or noise in the audio output.

Here's a picture of the finished panel:

Here's a look at the stripboard: I see from these pictures I added an extra opamp to the output but because I actually built this module a while ago I can't remember why I did that. Probably to have more room to experiment with the output and add the Gain potmeter. Anyway, it works the same so you don't have to include that.

And, to close off this article, I made a video demonstrating the different settings and the sounds they produce. As you can read in the article, I recently changed the GAIN potmeter from a 20K into a 100K one giving a total gain of up to 22 times. This gives the option of boosting the middle range of the Wavefolder which sounds really awesome!!

Here's a video that's also posted in the "Sample and Hold" article. It's a triangle wave going through the Triple Wavefolder and then through the Steiner-Parker filter, fed by random notes from the Sample and Hold connected to the CV-2 input of the VCO.

Okay that's an other project done. I hope you enjoyed it. Check out Adamski A. 's youtube channel. It is full of awesome synthesizer projects and electronics tutorials. It's an enormous source of inspiration for anyone interested in building synthesizers.

As always, any questions or remarks, please put them in the comments below or post them on the new EB Projects Facebook Group.