JH's wavefolder (link) variable distortion

[Paul Perry (Frostwave)]

http://home.debitel.net/user/jhaible/jh_wavefolder.html
Can't see that Juergen Haible's wavefolder B has been mentioned here before.. looks pretty intersting for putting 'hair' on your notes!

[MartyMart]

That looks really great !
And I have some TL072's ( same as a 353 ) and a ton of 1N4148's  !!

Thanks Paul, perhaps I'll vero a version this week ....... !
unless it "has" to run at +/- 15 volts.....

Marty.

[troubledtom]

looks cool!
  peace,
          - tt

[DiyFreaque]

On the subject of wave folders, there's also Ken Stone's stuff.  His CGS Metal Shop Wave Multiplier so blew me away, it was the very first module I built for my synth.  It is, from what I understand, a very close representation of the middle section of the Serge Wave Multiplier that JH mentions in his article.  The CGS29 also has an extra 'Grinder' section, which is a lag based distortion unit to throw high freq hash into your signal, which it certainly does.  In any event, I have nothing else in my arsenal that will do the things this module does - just watching on an oscope what this thing does to a triangle wave is mind-boggling.  I think it could do amazing things with a guitar, and also bass, though it would probably need some signal adjustment.

http://www.cgs.synth.net/modules/cgs29_wave_multiplier.html

Along those lines is a simpler, yet very effective circuit, the CGS52 Simple Wave Folder.  Simple is right when describing the topology of the circuit (take a look at the schemo!), but simple would not describe what it does - it sounds very cool as well, and this circuit can be chained up for more and more complex sounds.  Again, signal adjustment may be in order, but this might be a fun one to play with on the breadboard with a guitar.

http://www.cgs.synth.net/modules/cgs52_folder.html

Both of the circuits shape the output wave according to the amplitude of the input signal, so, like JH's,  it would 'follow' your guitar's signal, in a manner of speaking.  The CGS29 has an internal CA3080 based VCA so that you can control the number of folds with something other than the input signal.  On both, the DC offset control creates a very cool shift in the sound - very hard to describe - sorta like PWM, only different.

Cheers,
Scott

[puretube]

here`s a very early 1:
http://www.pat2pdf.org/patents/pat2689300.pdf

[amz-fx]

The problem with all of the synth wavefolders is that they were designed for an input signal with a constant amplitude, and a much higher amplitude than that which comes out of a guitar!   Signals with voltage levels different than the optimum for which the circuit was designed will perform differently, or not at all.

The solution, if you want to use one of these, is to put a compressor before the wavefolder and crank up its output volume.

regards, Jack

[Mark Hammer]

I was just about to post that before I scrolled down and saw your note.  That means I can only describe your post as genius, pure genius! 

The amplitude issues pose a constant problem to adapting synth modules/processes to guitar signals.  I guess it is easy for newbies/novices to forget, or not even know, that VCOs often pass through such filters and such BEFORE they pass through a VCA where an envelope is mapped onto the note.  The note coming out the speaker may decline in volume but what the filter sees does not; the VCO is constantly feeding the filter, even when you don't hear anything.  We hear a note go "pung!" on a synth, hear a guitar string go "pung", and assume that the two are similar sorts of signals.  Sadly the guitar signal you would feed to such a waveshaper would likely fall well below the critical amplitude needed to hear any effect almost immediately.

For a while in the late 70's and early 80's, Elektor had tons of waveshapers in their circuit collections.  I have a binder chock full of them. Almost all involve wacky variations on cascaded rectification stages.

[Nasse]

http://hem.passagen.se/robin2/im/hyperfuzz.gif

Dunno if i have money this christmas for the scanner, still don´t have it . I found some old eti magazines when cleaning house, and two fuzz circuits that I knew I put somewhere but almost thought i had lost them.

[Mark Hammer]

I have that article, and a scanner.  The board layout is kind of a strange one, that provides almost no choice about where to put your switch, pots, or battery.

[Ge_Whiz]

Experimenters should be reminded that Tim Escobedo's 'Tripple Fuzz' is a great, simple little circuit for turning waveforms inside-out.

[petemoore]

  Yes they specified much higher voltage than a pickup for guitar alone will put out.
  They also said something about intended Sine or Triangle wave input...
  Gaining input is just that and probably not too hard to exp with.
  I wonder what the expected folded outcome would sound like. I imagine [from the reads] it's similar in some ways to an Octave [unruly if the input is too complex], because it's intended to 'triple' or at least produce harmonically rich output compared to input.
  That said ,I have no idea what a wavefolder on guitar or other instrument would sound like.

[Vsat]

Actually these "wave-folding" shapers EXPECT to be fed a variable waveform level ... preferably something with a low harmonic content like a triangle or sine (rather than saw) for most obvious effect. A guitar signal should work quite well provided it is amplified up to 10V p-p or so. The Serge Wave Multiplier (the mystery middle section)  has a CA3080 which acts as a VCA to control the signal level going into the folder, normally supplied direct from a VCO. As the p-p level increases,  more "folds" are generated in the output waveform. The maximum number of folds  is limited by the input signal level, the thresholds used in the  folding circuits, and how much supply voltage the op amps can stand.
Cheers, Mike

[amz-fx]

I was just about to post that before I scrolled down and saw your note.  That means I can only describe your post as genius, pure genius!

Great minds think alike!   

For a while in the late 70's and early 80's, Elektor had tons of waveshapers in their circuit collections.  I have a binder chock full of them. Almost all involve wacky variations on cascaded rectification stages.

Sounds like ground for further experimentation...

regards, Jack

[Processaurus]

I've made Jeurgan Haible's Waveshaper A and B, B is great for guitar, its a unique sounding fuzz, with quite a few different sounds to offer.  Suprisingly some of them are  subtle.  At the most extreme you get a crazy filter sounding sweep as notes decay and the wave unwraps itself.  Odd phaserish sounds are possible too.  To interface the circuit with guitar you need a ton of gain, I started with an opamp stage with a gain of up to 100x, followed by a soft clipping stage with a switch to add in more gain (another 10x) for Mufflike sustain.   The wave folder section likes to see a sloped waveform, so the softer the clipping you can get the more you hear the wave folding.  Finally I changed R61 to 10K to add another 10x gain.  Thats a total of 10,000x gain available.  Just enough. 
I ran it off 9v with the Max1044 charge pump for the -9v supply.  Unfortunately the circuit draws about 25mA, half of which comes through the Max chip, and is close to the current rating for that IC.  Also I had to ground the IC right where the power to the circuit comes in, to get rid of a little whine at super high gain (in spite of the frequency multplier on the charge pump).

It works well with effects like tremolo or a volume pedal in front of it, or like Jack was getting at, a limiter (like the famous ross/dynacomp) followed by a volume pedal, so you could control the waveshaping with the volume pedal.

A couple ideas for future builders is to maybe try LEDs (if you can come up with 16 red LEDs) instead of Si diodes in the ladder, or better yet, make kind of a logarithmic ladder that starts with Ge diodes, then Si, then finally LEDs, so the wavefolding happens in a wider dynamic range.  A tone stack would be nice too, as the circuit by its nature adds quite a bit of high end garbly gook.  Also you could try adding a DC bias (or an LFO, envelope, etc.) before the wavefolder diode ladder to make one side of the waveform get folded asymetrically.

Be the first on your block to have one!

[Paul Perry (Frostwave)]

A couple ideas for future builders is to maybe try LEDs (if you can come up with 16 red LEDs) instead of Si diodes in the ladder, or better yet, make kind of a logarithmic ladder that starts with Ge diodes, then Si, then finally LEDs, so the wavefolding happens in a wider dynamic range. 

Maybe presistort the signal, before it gets to the wavefolder.

[Processaurus]

Maybe presistort the signal, before it gets to the wavefolder.

Interestingly the wave folder doesn't affect square waves at all, because all the folding happens too fast as the signal crosses zero.  A heavily filtered distorted signal though, muddy even (like a big muff with the tone knob turned all the way down), would be a different story.

Doesn't your Sonic Alienator do some wave folding effects by switching bits around? The perfect Chrismas gift for the little bit crusher inside all of us.

[Paul Perry (Frostwave)]

Doesn't your Sonic Alienator do some wave folding effects by switching bits around? The perfect Chrismas gift for the little bit crusher inside all of us.

Indeed it does, but ask Santa for some solder & DIY!

[SeanCostello]

here`s a very early 1:
http://www.pat2pdf.org/patents/pat2689300.pdf

This patent seems to implement "wrapping" or "foldover" distortion, rather than the "mirror" distortion of the Serge unit where the signal starts reflecting back. Useful for adding octaves to a sawtooth oscillator.

Foldover distortion can happen in digital systems in fixed point math, when saturation arithmetic is not turned on. I was developing a quick & dirty guitar distortion algorithm this summer, and performed a bit shift operation to increase the gain of the input, but without saturation arithmetic being turned on. The result was an INSANELY distorted signal, where picking harder would basically turn a guitar note into vaguely pitched noise. Using a saturating bit shift brought the signal back into the standard distorted realm.

The Serge wavefolder stuff produces sounds that closely resemble FM. If you FM a digital sine oscillator with a base frequency of 0 Hz, you get similar effects. Set the base frequency to 0.1 Hz, and you get a chorused version of the waveshaping. However, when you FM an oscillator with real-world inputs, sometimes the phase gets stuck in a weird place, so the decay of a note sounds really tinny and thin.

Sean Costello

[Tim Escobedo]

IMHO, the biggest downside to a synth waveshaper, when used for guitar, is that they end up being very high parts-count fuzzboxes. Perhaps there's something about the inherent dynamic and harmonic complexity of a typical guitar signal that "evens out" after such extreme distortion, which is what waveshaping is.

Not to say they're useless. I just personally found the Serge and J Haible circuits to be overkill, unless you really need specific things like CV inputs and/or particular transforms.

[moosapotamus]

Those plots on J. Haible's wavefolder page look kind of like Zach's description of what the Machine does. Is that kind of the idea, or am I mixing apples and oranges?

~ Charlie