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.

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:

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. But it all worked out okay. For the 1µF caps I ordered ten 1µF WIMA MKS box capacitors, 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 room 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.

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.

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 bipolar 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 but normal 1N4148 should work fine too.

 

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.

PICTURES:

Here are some pictures of the boards during testing and the finished product:

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.

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 cool video I found on YouTube explaining how this module works:

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.

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