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Rectifiers in modules
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author Rectifiers in modules
Blackened Justice
I'm sorry if my electronic knowledge is not the greatest, and I base my ideas purely on mental experimentation and not actual physical experimentation.

I don't know how wavefolders/multipliers are built, nor if it has anything to do with what I'm going to describe next, but if it does, please let me know. I feel it has something to do with wave folding, but I can't quite put my finger on it.

Anyway, the only module I seem to find in euroland that has a rectifier funtion implemented is Harvestman's Malgorithm, and I don't understand this. It seems like a great way to make complex waveforms from simple inputs, especially when done several times in a row. Let's say, you put a sine wave into the input, and you rectify it once, leaving you with something like this:

Then you add a negative DC offset to center the wave around 0 volts, and then amplify it to match the original signal's amplitude. And then run the new signal through another rectifier. This could be done several times in a row. With each sucessive rectification, the wave would get more harmonically complex.

Putting a triangle wave, however, results in sucessive frequency doublings, and inputting a saw wave would result in something that looks like a triange wave of half frequency. A square wave would obviously not work very well, unless the 5/-5 and -5/5 voltage gaps were long enough to actually get some sound out of it. So I guess it would produce very different results depending on the input wave, and I guess the harmonic enrichment would only work with either sine waves or some already harmonically rich waveforms (like FM'd/AM'd or RM'd sounds) or something like a VCS when used as a looping AD at audio frequencies and with exponential curves.

Anyway, just throwing an idea out there, I have no idea if any of this is even physically possible, just looking for some feedback.

Cheers
breakscience
You are kind of explaining half of a wave multiplier, without the dc offset? haha seriously, i just don't get it

With a wave multiplier when the threshold is crossed the wave folds back using the threshold as it reference point. If the amplitude of the wave is high enough to totally fold back past zero, then you will get similar waveforms to what you are describing here.

I hope that makes sense. But if not, you definitely want to read up on wave folders/multipliers, as it sounds like that is what you want...more harmonics.


Oh and, your method could work too...anything is possible!
I have worked out some of my wave shaping ideas in software. There are so many ways to screw with waveforms, just with simple tricks like you describe. Inverting, rectifying, amplifying, comparing, offset...very simple functions combined can have amazing results sonically.
ezekiel
Rectify, offset, rectify, offset, rectify, offset, ...

That sound like it would be a great mangler implementation. One knob per offset unit. Maybe each offset could be voltage controlled (that is, a VC adder).

Anyone with a bunch of Malgorithms and Analog Adder modules who can do the experiment and record some sounds? Or, someone with more electronics background?
neandrewthal
Sounds like an interesting approach as long as you amplify it afterward, because wouldn't it cut the amplitude by half each time?
wetterberg
I'm doing some experiments with a lovely object in maxMSP for this; pong~. I'll see if I can't grab some scope pics while I'm at it; doing multiple "wrappings" in a row is certainly interesting, at least on simple waveforms. Modulating the extra dc input really adds a nice warpiness to it.
BugBrand
You could try out ideas using the free Nord G2 Demo Software!
(always a useful test-bed for ideas)

Windows // Mac
Clavia Download Page
frijitz
Blackened Justice wrote:
Anyway, just throwing an idea out there, I have no idea if any of this is even physically possible, just looking for some feedback.

Your thinking is fine. I've worked on waveshapers for years. The Wavolver does a kind of folding, with the folding driven by an external CV rather than by the amplitude of the input:
http://home.comcast.net/~ijfritz/sy_cir6.htm

But my alltime favorite is the 5Pulser:
http://home.comcast.net/~ijfritz/sy_cir8.htm
This easily the most bang-for-the-bucks waveshaper around. Available through Bridechamber.

grin

Ian
Blackened Justice
Anyway, if this were to be implemented in a module, my suggestion would be to (as wetterberg said) modulate the offset after each rectification through a CV input, and maybe have "tapped" outputs after each rectification-offset-amplification stage. Another thing is, how many stages do you think it should have? I have no idea, maybe around 5, but then again why not 6, 7, 8, 9... What would be the number of stages after which the waveforms, even though they're visually different, are audibly the same? Maybe even an external feedback input, to create strange stuff.

I personally think it would be a very versatile module, especially with the way it handles different waveforms in very different manners. The fact that it would function as a frequency multiplier for triangles, a triangle-ifier at half frequency for sawtooths (in the first stage; then it would act as a frequency multiplier and a wave-shaper for sines and stuff I mentioned before. I think it would get very interesting with not only the dry wave-forms going into the input, but maybe post-filter (when you'd change the cutoff frequency or raise the resonance, you'd produce radically different waves), post frequency divider, or post another kind of wave shaper/multiplier.

Anyway, would anyone be interested in taking this project? I would, but my electronics skills as of this moment are pretty much non-existant.
Karl Jeffers
I just tried this in the G2 demo software.
It rocks SlayerBadger!
Pure waves, drumsounds, filtered waves, it all sounds very good.
I want one!
Blackened Justice
Could you post some sound samples, please? I really have no time right now to check out the Nord G2 demo, but I'd like to have an idea of how it sounds like.


Is there anyone interested in doing a module like this? Or at least teach me how to do it myself?
Luka
sure
just get the cgs wavemultipier pcb
http://www.cgs.synth.net/modules/cgs29_wave_multiplier.html
felix
Blackened Justice wrote:
Anyway, the only module I seem to find in euroland that has a rectifier funtion implemented is Harvestman's Malgorithm

I've never looked at its rectifying behavior on a scope, but however it does it, it does it well! It's one of, if not the preferred choice of distortion on the modular for me. Turning the input level down enough makes it almost act like a gate of sorts and you get these awesome bursty distorted sounds - especially if you're modulating a filter before the input of the Malgo.
Karl Jeffers
Luka wrote:
sure
just get the cgs wavemultipier pcb
http://www.cgs.synth.net/modules/cgs29_wave_multiplier.html

This looks to me like a ringmodulator.

I will post some sounds in a few days.
kkonkkrete
Blackened Justice wrote:
Another thing is, how many stages do you think it should have? I have no idea, maybe around 5, but then again why not 6, 7, 8, 9... What would be the number of stages after which the waveforms, even though they're visually different, are audibly the same?


Bear in mind that the entire range of human hearing is <10 octaves. Each stage doubles the fundamental, so it probably does not make sense to have more than a handful of stages. Tones with fundamentals above 10kHz all sound pretty much the same in terms of timbre.

Also, you might want to have a look at the Serge Wave Multiplier. The bottom section is based on repeated full-wave rectification + offset. IIRC, it has three stages. As rectification is one of the first things that EE students learn (half-wave rectification is just a single diode!), it's probably not that surprising that this has been in synths since the early days. Still, lots of potential for experimentation if you have VC offset between stages, or feedback as you mention.
Karl Jeffers
I am not able to record the G2 demo software, but I have the patch.
nP
In case someone gets bored and wants to fiddle around with a fairly messy implementation of the general idea, go to http://falstad.com/circuit/ and import the attached schem.

edit: New versions added.
daverj
the two diodes on the left half of each bridge (going to ground) should be removed.
nP
[x] Copy and paste considered evil.

It's just meant as a little toy to show what the "wavefolding" does and far from being a usable schem wink
ersatzplanet
Karl Jeffers wrote:
I just tried this in the G2 demo software.
It rocks SlayerBadger!
Pure waves, drumsounds, filtered waves, it all sounds very good.
I want one!


I love this piece of software. I really wish that since the G2 is out of production that Clavia would develop the demo into a full featured product. Allow it to connect to as many outs/ins as your system uses for instance. I have done Volta like things with it and it works great but is limited to just two channels. Make more modules and they have a update path. They have the thing 90% towards a viable software product that they could sell - such a wasted possibility. It is just SO EASY to patch things up on it.
-James
Blackened Justice
Hello again, I've been fiddling with the idea of making one of these for myself, I posted a topic in the DIY section requesting help in drawing the circuit schematic, but I was hoping for some opinions from people in general. Here is the link to the thread with all the details: https://www.muffwiggler.com/forum/viewtopic.php?t=10349
jjclark
Rather than offsetting each time, you could just use AC coupling. This would make for a simpler circuit.
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