Synthesizer Build part-63: FASTEST ADSR IN THE WEST by Rene Schmitz.

The fastest ADSR in the West. A simple to build and fully featured Envelope Generator. I thought it was about time for another ADSR project for the website and this one worked out great and it has no trimmers to set. I even added a few extra's to make it even better.

This is an other 7555 based envelope generator like the YuSynth one from project 24. Some people seem to have problems with that one so that's why I choose to do this project now.

This ADSR will work on both +/-15V and +/-12V. At +/-12V the maximum envelope amplitude is just under 8 Volt. If you run it on +/-15V the peak envelope value will be 10 Volt. It's a very fast Envelope Generator. The minimum risetime of the signal is 1mSec or 1/1000th of a second.

Now this is roughly the same setup as in the previous 7555 ADSR from project 24 but it does work a lot better, especially when using Schottky diodes. The whole problem with the DC offset voltage left on the ADSR output comes down to the forward voltage drop of the diodes. That's why Schottky's are so useful because they have only a third of the voltage drop of silicone diodes. Now what would be even better is to have diodes with no voltage drop. To achieve that we have to put the diodes inside the feedback loop of an opamp. That's what happens in the Kassutronics Precision ADSR which I recently also added to the website as project number 67.

So this ADSR and the Yusynth 7555 ADSR have become a bit obsolete now, eventhough they work just fine for use with VCA's and for Filter CV signals. I would advise anyone wanting to build an ADSR to go to project 67 and build that one.

SCHEMATIC:

Here is the schematic for this circuit. I've redrawn it from the sketch posted on Rene Schmitz website.

The opamps are numbered in the order they are used on the stripboard. All diodes have been replaced with Schottky diodes which work much better in this circuit.

Click here for a FALSTAD SIMMULATION of this circuit.

I've added some extra's to this design. The original design only uses two opamps but I wanted to include a LED and also an inverted output so I decided to use a quad opamp, the TL074, and include an attenuverted output where you can have in inverted envelope signal with the potmeter turned fully counter clockwise, attenuation with zero signal when the potmeter is at the 12 o'clock position and a normal envelope when the potmeter is turned fully clockwise. I took the design from the AD/AR attenuverter mod from Ole Stavnshoej design (project 44). This is a great option to have when you use the ADSR with a filter. Turning the attenuverter will give the filter some very cool resonance response.

I decided to adapt the design to more run of the mill parts, like for instance I used 1M potmeters instead of the 2M2 ones in the original schematic. I changed the 220Ohm resistors to 100Ohm types and the capacitor from 2µ2 to 4µ7 to keep the original timebase intact. This is all explained in the text underneath the original schematic on the Schmitzbits website.

The circuit is relatively simple so I was able to build it up on a very eurorack friendly sized piece of stripboard. It's only 21 strips by 33 holes. Although I left the V,W and X strips on the board, they are not populated. You can use them to connect L brackets to mount the board to a panel. The three transistors on the Gate input represent the same setup as we've seen before in the Yusynth 7555 ADSR only there he had no resistors at the base of transistors 2 and 3. It works as follows: the first two transistors make up a schmitt trigger which turns any input signal into a sharp gate signal. That signal now goes through a capacitor that turns any long gate signal into a short pulse. That pulse is inverted in the third transistor stage to make it acceptable for the 7555 chip, going in at pin 2. 

Once the ADSR has been triggered the sustain level for that cycle is frozen. You can not add sustain while the ADSR is in its cycle, unlike the Digisound ADSR which can do this. Not that that's important. it's just something I noticed while testing the circuit.

The 1M resistor, in red on the schematic and in purple on the layouts below, can be added to provide for some input hysteresis. This will improve triggering on slowly changing waveforms. In the layout below, the purple 1M resistor on the left indicates where it should go if you want to include it. I left it out. Only include it if you really think you're going to need it. If in doubt, Leave it out.

LAYOUTS:

Here are the layouts I made for this project. As always they are verified. I used them to build my module. It's important to use logarithmic 1M potmeters for Attack, Decay and Release. The time based parameters. Otherwise it will be much more difficult to set these parameters accurately. It will work with linear types but get logarithmic pots for these. Sustain is a level control so that can and should be a 10K linear type potmeter.

I used Schottky diodes throughout this design because with 1N4148 diodes there's a DC offset voltage present on the output. Using Schottky diodes helps to prevent that.

Wiring diagram:

Stripboard only:

Again, leave out the purple 1M resistor unless you're going to feed this ADSR with slowly changing Gate input signals. Nor likely so leave it out.

Cuts and wirebridges seen from the component side. You know the drill by now; mark the cuts on the component side with a Sharpie or Edding pen and then stick a pin through the marked holes and mark them again on the copper side. Then cut at the marked places with a sharp, hand held, 6- or 7mm drill bit.

Here is the Bill of Materials. I altered the diode types to Schottky diodes because they will work much better in this design. I put in the BAT4* series (like: BAT41, BAT42, BAT43 etc) because they work really well and have good availability in webshops. Any Schottky diode will do though.

OSCILLOSCOPE IMAGES:

Here are some screen shots from my oscilloscope to give you an impression of what the signal looks like. All testing was done with a +/-12V powersupply:

Here's the normal envelope output. The envelope signal does have a small positive offset voltage of 400mV I noticed. But this won't cause any VCA to stay open so it's of no consequence. 

However I changed the diodes for Attack and Release into Schottky diodes and that reduced the offset to just 16mV (16 thousandth of a volt) which is the same as 0V to me. The offset voltage is the result of the fact that the 4.7µF cap has to discharge through a diode and a diode has a voltage drop over it of about 0.6V (with silicon diodes). So the lower that voltage drop the better. With Schottky diodes the voltage drop is only about 0.2V which allows the cap to discharge as good as fully.

Here's the normal output in yellow and the inverted in blue coming from the attenuverter mod I added on myself. It works like a charm.

Here you can see, in the blue trace, the attenuverter in action. I'm turning the potmeter as the trace goes from left to right.

This is the signal at a pretty high rate at almost 3Hz. No problem for this ADSR.

In yellow you can see the pulse as it comes out of the third transistor and into pin 2 of the 7555. It's a inverted pulse, triggered by the gate signal, that starts the ADSR.

This time the yellow trace is the gate signal at the input. This was measured after the 10K input resistor. The gate signal was a +/-5V pulse wave from an LFO.

PICTURES:

Here are some pictures from the build proces.

Stripboard with cuts and wirebridges done.

Finished stripboard ready for wiring up.

All wired up ready for testing

I decided to use this ADSR for my DIY Kosmo synth and not for Eurorack so I took the YuSynth ADSR and replaced the stripboard with this one. I had to widen one hole to fit the attenuverter potmeter to which I added a bi-coloured LED to fill up another hole where a switch had been. I used a 4K7 resistor to connect it to the attenuverted output socket. I also re-used the manual trigger button that was already present in the panel. I took two 47K resistors and made a voltage divider so when I press the manual trigger it sends 7.5V to the gate input. (My DIY synth runs on +/-15V mostly).

Backview of the panel:

Here's what it now looks like mounted into the synth. My ADSR module has two Gate inputs each with a Schottky diode in series with the socket (soldered straight to the socket). This is to prevent +7.5V entering the Gate socket when I push the manual trigger button.

Luckily I could re-use the potmeters, which were 1M logarithmic types with a 10K linear pot for the sustain, the same as in this project.

You can see the blue LED underneath the attenuverter potmeter. The hole I had to fill up was 6mm and this LED is only 3mm so I used hotglue and made a sort of white blob that lights up red or blue. Worked out pretty well :)

I kept the dual gate inputs from my previous ADSR because I think it's handy to have. The gate inputs have Schottky diodes on them so that when I push the manual trigger button I don't get 7,5 Volt pushed into the gate patch cable(s). It's a safety feature I advise you to copy if you are going to include a manual trigger button.

Troubleshooting tip: If your Decay and Sustain are not working then the most likely cause will be a broken Sustain potmeter. It happend to me when I built it into the panel I used for the YuSynth 7555 ADSR and it turned out it had a broken Sustain potmeter all the time.

DEMO:

Here's a video I found on YouTube of someone demonstrating this ADSR in action. He's using it on the cutoff of a lowpass filter. Sounds pretty sweet. If he had the version with my attenuverter mod it would have sounded even better LOL ;) 

So that's another one done. I thought it was about time for a new ADSR project on this website, especially since some people seem to have problems getting the YuSynth 7555 ADSR of project 24 to work right. That's weird though because I always rated that one as near perfect but I think this will make an excellent alternative especially with the extra's I added. I'm really chuffed that it worked so well. Okay, I hope you will enjoy building this one. 

If you have any questions or comments about this project then please post them in the comments below of on the special Facebook group for this website.

If you like this content and would like to support the work I do here then you can buy me a coffee. There's a button for that underneath the menu if you're on a PC or Mac. Otherwise you can use this Paypal Me link and cut out the middle man. All donations go straight back into new projects and the upkeep of the website. Thank you!!

Synthesizer Build part-62: 2164 VCF/VCA by Thomas Henry.

This is the Fonitronik Thomas Henry AS2164 state variable filter and VCA in one. THIS FILTER SOUNDS DELICIOUS!!  It's a great sounding combination. I used two stripboards that connect together with pinheaders making this a very eurorack friendly design. However this is not a beginner friendly project. You need good soldering skills for this one. Even for me this was not a 'hole in one' like a lot of the previous projects. I made a few mistakes but I found them in the end so all is well. But this project is certainly in my top 5 of best projects on this website.

EDIT: 8-April-2025  I forgot the current limiting resistor in series with the LED on the filter. I have now put in a 1K resistor and updated all the layouts etc.

This filter uses the AS2164 or V2164 chip which, in its original form, was a chip from SSM (Solid State Music). These chips were used in many late 70's polyphonic analog synthesizers like the Prophet 5 for instance. The V2164 is made by CoolAudio which is a company owned by Behringer which they use to create all the old obsolete chips for Behringer's line of vintage synths that they are reproducing.

The 2164 is not actually a filter chip. It has four independent VCA's on board and in this design two of those are used to make a great sounding 2 pole filter (12dB/Oct.).  This filter has that vintage liquidy feel to it when you add a lot of resonance. It sounds amazing.

The left over two VCA blocks in the chip are used to make a single VCA. Of course you don't have to build the VCA if you don't think you need it. You can build just the filter board if you want. However you can not only build the VCA board (using my layouts) for the obvious reason that the 2164 chip is housed on the filter board.

The V2164 chip is very sensitive to missing negative voltage. If negative voltage falls away the chip will be distroyed. There is a diode in the layout that protects the chip however.

If you buy the AS2164 instead of the V2164 then you don't have to worry about this because the AS2164 has internal protection against negative voltage cut out built in. BTW, you can buy the chip(s) from Electric Druid amongst other.

Here's the finished module (on the right) fitted into a Nifty Case. Dispite the depth it still easily fits.

Here is the schematic:

This project will run on both a dual 15V or a dual 12V powersupply. It's designed for 15V as you can see on the schematic but I built it for Eurorack dual 12V and it works fine.

As you can see it's quite a simple design and in my experience those produce the best sounds. The top part of the schematic shows the filter and the bottom part the VCA. I decided to make the two parts that make up this module on two separate pieces of stripboard so that I could make them small enough to fit flat behind a 14hp faceplate, with one board on top of the other. They connect together using pinheaders. The VCA board is connected to the 2164 chip via those pinheaders. The depth of the finished module will be around the 4 CM mark.

LAYOUTS:

Below are the layouts I made for this module. As always they are verified, I used them for my build.

Here's an overview of both boards. In the layouts you can see a Coarse and Fine control for the filter cut-off. The fine control is there in case you want to use the filter as an oscillator in full resonance, so you can tune it, but I never use a filter like that so in my own project I switched the 3M3 resistor for a 100K one and put in an extra socket so I can use that as an extra CV input with level control, So the potmeter labelled as Coarse is in my case labelled as 'Cutoff' and the 'Fine' control is now my CV2 Level potmeter. I placed it all the way down on the faceplate. 

The PTC is an other component you don't need if you don't want to use this filter as a sinewave oscillator. Just put in a 2K resistor instead. That's what I did too. There's also a 7K5 resistor which I coloured purple, in the layout. Leave that out too. If you include it you change the VCA amplifier type from a class AB to a class A type. Totally unnecessary.

I used miniature potmeters in this project to save space and I made my own custom potmeter symbols in the layout software, the little green ones.

Here's the wiring diagram for the filter part. All potmeters are viewed from the back. It may look to you that the Resonance potmeter is wired the wrong way around with ground at the clockwise position but I found out that this is the right way to do it. Resonance is usually wired the other way around in most filters. This filter, I have to say it again, sounds sooo good. I love 2164 based filters and I think this is now my favourite filter on the website. It has a liquidy watery feel to the resonance which is just amazing. Anyway..... here's the layout.

VCF stripboard only view:

Below is the wiring diagram for the Linear VCA part. The VCA has two audio inputs. One direct input without level control which is intended more for LFO signals. On the Fonitronik panel it is labelled as DC IN. In my design I did give it a level control but that potmeter is not on the layout. The top audio input has a level control and an AC/DC switch. AC is usually used for audio signals, filtering out any DC components like offset voltages that might be present. DC is used for very low frequency signals like from an LFO or envelope generator. The VCA is very snappy, it can switch on and off very fast so you can use audio rate signals to open and shut the VCA and get a sort of ringmodulator effect.

The 'initial' potmeter regulates the output volume of the VCA by adding an offset voltage to the envelope input. You can use it to open the VCA without pressing any keys so you hear continuous sound. If you close it the sound will only come through when you press a key and an ADSR signal comes in on the CV input. At first this didn't seem to work but I made a mistake. I had this VCA connected to the Gate Out of my sequencer and the audio out went to my other VCA. That didn't work well and VCA wouldn't open if I pressed a key. So I had two VCA's in series. My mistake.

(Last revised: 16-12-2024: The two potmeters with ground connections were wired the wrong way around. That is now corrected)

I know that in the schematic the 'Initial' potmeter goes through a 300K resistor and not a 100K like on the layout but I lowered it to 100K because that worked better for me.

VCA stripboard only view:

Here's an overview of the pinheaders, wirebridges, and cuts to be made for both boards, seen from the component side:

The VCA board has male pinheaders soldered directly to the copperside so the board connects to the filter board with the copperside facing the component side of the filter board.

This is a bit fiddly to solder, especially because I used a double row of pinheaders to make sure the connections are solid. I used the same method I used with the wavetable oscillator. I put some solder down between the holes where the pins sit and I put some flux on the solder part of the pins and pre-soldered them too. Then I put them in place and I only needed to heat the solder already there to make them connect to the stripboard. Do this before you solder in any components so you have enough room to work and fit the two boards together regularly to make sure it all aligns like it should. 

Be careful not to overheat the pinheaders because the plastic that holds them together can melt. When I solder male pinheaders I always connect female connectors to them so the heat can be absorbed better.

Finally here's the Bill of Materials:

You can use other types of Schottky diodes if you want, like the BAT41 or 42, 43 etc. It doesn't matter as long as they are Schottky diodes.

PICTURES:

Here are some pictures from the build proces:

The stripboards with wirebridges installed:

Here's how I soldered on the male pinheaders:

Both boards finished but without their chips. I only put those in at the last moment to prevent damaging them.

The faceplate with the holes drilled in and de-burred, with the waterslide design applied to it. You can see there are still some bits that are not completely flat but when it is dry it will all be tight.

As you can see in this picture it dried up beautifully. Now to cut out all the holes with a very sharp hobby knife and then give it a few more layers of lacquer.

Here's the end result, not yet wired up. I put in two 3 CM M3 bolts with counter-sunk heads and screwed them tight with nylon ringed locknuts. Then I put some white paint over the heads and applied the waterslide paper overtop of that. It doesn't make the screw heads totally invisible but it works. I forgot to put in a hole for the 3mm LED. I later drilled one in just underneath the top text.

While I was waiting for some components to come in the mail I wired up the backside of the panel as far as I could. I connected all grounds together with one copper wire and I also soldered all the potmeter pins that needed to be grounded to that same wire. This way I will only need one ground wire going to the stripboard to ground everything. This is how I usually wire up ground connections. Do not rely solely on the metal of the faceplate to be the ground. Remember Aluminium oxidizes and oxides are not good at conducting current.

When all components were in, I wired it all up which took me almost a whole day and then I plugged it in and.... it didn't work at all. I tried to troubleshoot it, I posted in the Facebook group about it but it wouldn't work. Then I left it for two days and came back at it with fresh eyes on a sunday morning and I found the mistakes within half an hour. I made two little errors in the layout and I soldered one wire to the wrong place and I forgot to connect the ground copperwire, which has all the socket grounds and potmeter grounds connected to it, to the stripboard. After I corrected that, it all worked fine. Strangely enough the missing ground wire connection was something I noticed later on, but even without a ground connection everything worked! I was really surprised by that.  

Btw, I normalled the lowpass output of the filter to the input of the VCA so the filter output is automatically enterred into the VCA. You can of course also choose to normal the VCA output to the input of the filter but I've tried that and I didn't like it. It's more conventional to have the filter out go into the VCA in. To replicate this all you have to do is solder a wire to the audio output of the VCF and then solder the other end to the switch connection of the audio input socket of the VCA. When no patch-cable is connected to the VCA audio input, it gets its audio from the VCF output. If you connect a cable to the VCA input that VCF connection is broken.

Here's a look at the finished module:

As you can see, the boards bend back a little because they are only connected to the panel at one end and there are a lot of wires pushing it up. To pull the other side down, I soldered a wire from the socket ground to the ground of the eurorack powerheader. These points are directly above eachother and the copper wire now pulls the boards down which looks better and helps keep the depth to a minimum. It also takes care of grounding everything on the panel.

It is still a pretty deep module. It's 47mm deep. But it will fit most eurorack cases like the Nifty Case. 

VIDEO:

Here's a cool demo video I found on YouTube by Fonitronik:

A few final notes:

I based my panel design on the original Fonitroniks panel and the labeling on that is somewhat different than on the schematic. This caused me some confusion as I only really noticed it after I had finished the panel. For instance the DC IN on the VCA is actually an extra audio input that can also take CV signals. The Linear AM on the schematic is labelled Lin. FM on the original panel. So I would advise you to keep to the labeling of the schematic and the layouts and not use the Fonitroniks panel as inspiration, like I did.

Here is the original panel of the Eurorack module:

Note how it says Linear FM at the bottom right input but with a VCA the control voltage influences the amplitude or volume of the output, not the frequency. So it should be AM.

Here's an explanation of the input options of the panel design above. They can be very confusing.

I took my panel design and added more understandable labels. It used to look like the design above here but I think this will make more sense. There's four designs for an A-4 sized waterslide paper so you have some spares should you mess up. I also added a place for the LED which is connected to the filter CV-1 input (that's the envelope input for the filter). This image is to scale for a 14hp Eurorack panel. You can save it and print it out onto waterslide paper and use it to make you panel.

Okay, that's it for this one.

If you have any questions or remarks about this project then please put them in the comments below. Comments are moderated and don't appear until I approved them which can take a while if you're in a different timezone than me. You can also post questions or show your work in the special Facebook group for this website.

If you like this content and would like to support the website and future projects, you can buy me a coffee. There's a button for that underneath the main menu if you're on a PC or Mac.

Otherwise you can use this PAYPAL.ME link and cut out the middle man. All donations go straight into future projects and the upkeep of the website. Thank you!!

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.

If you like this content you can support the website by buying me a coffee. There's a button for that underneath the main menu.