Synthesizer Build part-41: METALIZER by YuSyth.

A module out of the wavefolding stable only this one sounds really sharp and metally, hence the name. It's quite an easy build too although it does need two pairs of matched BC547 transistors. It's more or less a quadruple wavefolder with a Voltage Controlled Amplifier on the input which is controllable with two attenuated CV inputs.

This Yusynth module was something I hadn't come across before because it is not on the YuSyth main website, at least not in his projects menu which is where I normally look. Someone posted a link to this module on Facebook and I thought it would make a perfect little project.

Yves Uson (YuSynth) designed this Metalizer for the Arturia MiniBrute and MicroBrute and he says it's now one of the most characteristic features of those two monosynths. I think this will be a great addition to any modular system. It's like a Heavy Metal guitar pedal for synthesizers =)

When I started building this project I went about it much too hasty and I had made about six or seven mistakes when I first tried to test it. I had forgotten cuts, misplaced wirebridges, used the wrong transistors in the wrong place, the whole shabang. But luckily, over time, I've become quite good at troubleshooting and I recognized the mistakes pretty fast when going through the schematic and comparing it with the layout. The final mistake was a cut I had forgotten that connected the -15V to the base of transistor Q2 which generated a enormously loud buzz. I detected that by using the 'Highlight Connected Areas' function of DIYLC, the layout making software I use. Once I cut that copper strip the module sprang to life. It sounds pretty cool  It's much like the other wavefolders on this website but this one has more harmonic distortion and much more complex waveforms. It sounds buzzy-er, gritty-er more metal like, sometimes more ring-y if you know what I mean. 

If you read the 'Triple Wavefolder' article you might remember me speaking about having a VCA on the input to control the input level and with that the number of folds the waveform undergoes. Well, this Metalizer has a built-in VCA on the input that is controlled by the CV-1 and CV-2 inputs. Also, the audio level doesn't change if you turn the 'Wave Folding' potmeter which is a problem that the triple wavefolder does have.

Btw, it is not possible to have a clean signal come out of the module. In other words, the effect is never truly off. Even with the folding-potmeter set to minimum there's still a good bit of wavefolding going on so if you want to be able to have a clean output you can include a bypass switch or a Dry/Wet potmeter, but you'll have to figure out how to do that yourself. It's not included in this project. However it's very easy to do.

Tip: this Metalizer is particularly useful if you make drone like, continuous sounds with your modular synth. Having it produce a constant noise and modulated by a slow sine or triangle wave from an LFO can produce some very cool results especially if you are into more heavy, distorted sounds. You can also vary the frequency of the VCO going into the Metalizer by connecting the VCO to a slow LFO signal too and have the two interact that way. Enough ways to experiment with this awesome module.

Like the other wavefolders, this module works best if you feed it a Triangle- or a Sinewave. 

The module is meant to work on a dual 15 Volt powersupply but will work fine on a dual 12 Volt supply.

The build proces was quite straight forward. One of the things you need to look out for is the 680nF capacitors. Those are values that are not often used in synthesizer projects. I think this is the first one on this website that uses 680nF. The only ones I had were some very big ceramic ones but I didn't have enough so I had one capacitor that I made up out of two caps mounted in parallel. I didn't account for the size of those capacitors in the layout but if you order new 680nF caps they will fit fine in the space allocated to them in the layout. The new ones are much smaller than the old stock I had. I later found out that the exact value of those capacitors is not that critical. You can use anything between 560nF and 1µF as long as it's non-polarized.

You might think 'I'll put a level potmeter on the input so I can control the volume' but don't do that! That function is already covered by the built in VCA so keep to the design as shown on the layout and schematic.

LAYOUT:

Here is the link to the schematic in the YuSynth article. It also has PCB layouts, if you want to make your own PCB for this module, and it has the panel design which I more or less copied for my own panel.

Here's the layout, wiring diagram. I've added a Eurorack connector just in case you want to use that. The metalizer will work fine on dual 12 V too. You'll need to flow the 3 ground positions underneath the connector together with some extra solder.

Stripboard only:

THINGS TO LOOK OUT FOR:

Beware, the first two pairs of BC547's need to be matched. Q1 and Q2 is one pair and Q3 and Q4 the other. I matched them with my transistor curve tracer on the oscilloscope but you can use the method I used with the TB303 filter and the ARP2600 filter. That's the Ian Fritz method. You'll find a description of that method in the aforementioned articles.

An other thing to keep in mind is this: if you look at the output of this module when there is nothing connected to the input you're going to see a very noisy squarewave-like waveform on the scope. This is normal. As soon as you plug in the input everything will be back to normal. It doesn't help if you connect the input to ground with the built in socket switch, if there's no cable connected to the input. I tried it but it makes no difference. It's just a design flaw but harmless although you will hear this noise if you have the output connected to the audio in the rest of your synthesizer. So when no input is used the output must be disconnected or the Metalizer channel of the mixer must be muted. You know what I mean, right? Or you can use it as a quircky noise source ^____^

Here's a picture of the oscilloscope screen, probing the output without anything connected to the input. You can see how noisy the curve is:

ABOUT COMPONENT VALUES:

The potmeter values in the circuit are not critical because they are just used as voltage dividers here so you can use any value you happen to have lying around. I would advise to keep them in the 50K to 1M range though. That should work fine. The value of the 680nF capacitors can also be varied. Values between 680nF and 1µF will all work fine as long as they are not polarized so if you use 1µF caps they can't be electrolytic capacitors. They must be non polarized. The output capacitor of 10µF is an electrolytic capacitor but its value can also be varied. Anything between 4,7µF and 10µF will work just fine. Make sure the minus pole is towards the output socket.

Luckily there are no trimmers in this circuit so there's nothing that needs tweaking or tuning. 

Here's an overview of the cuts and the wirebridges. Mark the cuts with a Sharpy (water proof felt pen) on the component side of the print first. Then stick a needle through the marked holes and mark them on the copper side. Then cut them with a hand-held 7mm drill bit. 

Cuts only, viewed from the COPPER SIDE:

Bill of Materials:

Here are some pictures of the finished product: Note the enormous size 680nF caps I had to use because I didn't have anything else in stock. However, going by the Falstad simulation at the bottom of this article, the value of those capacitors does not have a big influence on the shape of the waveform. I tried inputting 370nF caps and the output waves were practically the same as with 680nF caps.

Here's a little demo video that I made of the very first test of this module. So this was the first time I had it switched on and connected to a VCO. Also, I only had one hand free to turn the knobs and play some notes on the keyboard, having the camera in my other hand:

Here's an other demo video I found on YouTube (not by me) which shows the Metalizer in action with a sequencer attached. The Metalizer is the second module from the left, marked "Metawave" (the one lying flat on the table):

Here are some screenshots of the oscilloscope showing the characteristic waveforms that come out of the Metalizer. They are very spikey sharp waves with loads of harmonics. If you put a conventional Lowpass Filter after the Metalizer you're going to get mid to high frequency sharp sounds out of it that sound pretty cool but there won't be much variation when you turn the 'Folding' knob on the Metalizer. In my opinion it's better to use this on its own, not in combination with a filter unless those sharp sounds are what you're looking for. They sound very musical. Almost like an FM synthesizer. The waves in the pictures below were all generated by putting a Triangle wave on the input and then probing the output.

I made a Falstad simulation of the Metalizer and when you run it you can see it produces exactly the same waveforms as on the oscilloscope: 

  --- CLICK HERE TO OPEN SIMULATION ---

Okay, that was article number 41. I will take it easy for the coming time because I have run out of some essential components and materials like the powdercoated aluminium strips I use to make my panels from and some electronic components. I'm even out of Hook-up Wire. I used a shielded cable with 8 wires inside as a source for hook-up wire. I had 68 meters of it and it's now all gone. That means there's over half a kilometer of wire in my synth now, LOL. So I need to replenish my stock and I also just acquired a VC340 Vocoder (such a cool piece of kit!) so I need to take it easy on the wallet too, LOL. You know how it is with this hobby, LOL :)

If you have any questions or remarks about this project please put them in the comments below or post them in the special Facebook Group for this website where we have a very cool little community willing to help you with any questions you might have.

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.

Synthesizer Build part-28: WAVEFOLDER (Yusynth design).

Here's an alternative way to create awesome synthesizer sounds! It's a pretty easy project to build too.

After first experimenting with a wavefolder design I found on YouTube I decided to build the Yusynth version because I wanted this option in my synth. This circuit produces some awesome and very divers sounds and waveforms.

This is a really good sounding wavefolder with a VCA on the input so there will be no changes in audio level when you turn the 'Shape' knob. It has a different approach to wavefolding than the Triple Wavefolder and the Metalizer circuits which you can also find on this website. The addition of the diode ladder and the clamping diodes on the output opamp give this wavefolder a very distinctive sound which I personally really love. See the demo video further down the article.
The build was pretty straight-forward and it doesn't need to take up much room in your modular set-up either. This is a beginner to medium difficulty project but you do need to have a scope available to calibrate the circuit. A 20 dollar cheap one will do nicely. Make sure you use multi-turn trimmer potmeters for this. That will make it easier to calibrate later on. You can use normal trimmer pots if you have no multi-turn ones but it won't be as accurate. The schematic says to used matched pairs of diodes in the diode ladder but when I measured them they were almost all the same voltage drop. So as long as they come from the same batch I think you needn't bother with matching. The two transistors Q1 and Q2 need to be matched also but you can use the transistor tester in your multimeter. I recently built an adapter to change the pinout of my power supply bus system so I can test modules on dual 12 Volt and I'm happy to report the wavefolder works just as well on 12V as it does on 15V without any changes.

Here's the schematic I used from the Yusynth website:

Here's the (verified) layout I made for it and which I used for this project. These layouts have been updated on June 12th 2023. I made some cosmetic changes to them and colour-coded the wirebridges and removed the coloured bands from the resistors so the values are easier to read.

Wiring diagram:

Stripboard only. Beware that some stripboards are sold with 56 instead of 55 holes horizontally. The layout is 55 holes wide:

Cuts and Wirebridges seen from the COMPONENT SIDE! As always, mark the cuts on the component side with a waterproof Sharpie and then stick a pin through the marked holes and mark them again on the copper side where the pin sticks through. Then cut the marked holes with a sharp 6 or 7mm handheld drill bit.

Bill of Materials:

This wavefolder works best if you feed it a triangle- or sine-wave from an analog VCO or waves from a Wavetable Oscillator. This is convenient because an analog filter works best with square-waves and ramp- or sawtooth-waves, they have the most harmonic content and triangle- or sine-waves don't work that well in a filter. So with the wavefolder we have a use for those triangle and sinewaves. Ramp- or sawtooth-waves will sound good too through the wavefolder but square-waves pass through the wavefolder unchanged.
Here's a video demonstration of the type of sounds I'm getting from this module using a triangle-wave only. There's also a very low frequency LFO ramp signal going into the CV input.:

CALIBRATING:
To calibrate this Wavefolder you will first need to set the two trimmers in their middle position. Turn the Shape potmeter all the way counter clockwise and Range all the way open (fully clockwise). Connect a sinewave from your VCO to the input and a scope to the output and turn the 1K trimmer (above the two transistors) to get the best looking sinewave possible.  It will probably not be a perfect sinewave but try to get the top and bottom part to look the same. Once you set this, turn the Range potmeter all the way counter clockwise and turn the 50K trimmer so as to just mute the signal, so the level is 0 when the Range potmeter is turned all the way left (counter-clockwise).
That's the calibration done.

Here are some pictures of the finished product:

This is what your soldering should look like:

Finally, here's a video I found on YouTube demonstrating the Wavefolder:

Okay, that's an other one done. A very worth while addition to the synthesizer. I can really recommend it and all you need to build it are some very common parts.
As always, please put any questions or remarks in the comments below.
Thanks for checking it out. See you on the next one!