Monday 22 March 2021

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.

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:

Print only:

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 Hfe transistor tester on your multimeter (if it has one). You can also get dedicated transistor testers for cheap on eBay that'll do the job nicely too. Just test them and pick the ones that have similar readings.
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:

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: 

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.

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  1. thank you so, so much for this. i was literally just scratching my head trying to lay this one out for my first try at doing a stripboard diagram.

    1. Thank you Phil! I'm glad you discovered this article just when you needed it =) Let me know if you have any questions about it.

  2. I'm on 12V, do I have to reduce R5/6 to 12K, R21/22 (and alike) to 18K, R13 to 220K?

    1. No you don't need to change anything. It'll work fine on 12V as it is.

  3. Hi Eddy, fabulous site
    Watching my Metalizer vid reminds me I still need to service my scope!!!

    1. Hi Simon! Service your scope? I didn't know you need to service them ^___^

  4. Hi, do you think it would work with 2n3904 / 2n3906 transistors ?

    1. Hi. I think it'll work fine. There might be a difference in the number of foulds you get in the signal but I don't think it'll be a big difference. Try it, and let me know what you get please. Would be interesting to add to the article.


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