waveshapers/wavefolders for guitar in 2009?

[Mark Hammer]

Waveshapers and folders strike me as being really more directed at waveforms/signals that are much more stable and consistent than what a guitar string provides, the idea being that manipulation of a wave, in real time, would add some animation to an otherwise "stagnant" signal.  As well, insomuch as a great many waveshapers rely on diode arrangements to divide incoming signals into components that can be manipulated in some way, it is assumed that the signal has to be above some critical level, and not fall below that.  Unfortunately, guitar strings decay quickly.  One can maintain a constant high level by means of compression and overdrive, but there you've already altered the harmonic content of the signal.

I have one of the Korg PME 40X "Waveshaper" modules, and it's not really much more than a fancy fuzz.  I mean, it does provide different fuzz characters, but they are not dynamically controllable, and not the sort of thing that elicits a "Wow, where has this been all my life?" reaction.

[nocentelli]

you can get away with +/-7.5v rails when using 1.5v dropout op-amps (TL072, etc ...).
onset of full-swing range is about 10vPP (seen at the input side of the 100r resistor)
that's a voltage gain of x100 when starting from 100mV single-coils...

Thanks! I read somewhere that synth signals from the standard Eurorack +/-12V systems tend to be between 5-10v; I will be using humbuckers (plus other signal boosting stuff - see below) so a single opamp might work ok if it can dish out 7.5v.

the other challenge here is current levels drawn from input source buffer/amplifier
sims show +/-10mA at onset of full swing range and getting worse from there
I can see a design alternative yielding about 1/3 the required input for onset of full-swing range
that's at least more manageable on the gain side of the equation (x33 gain relative to 100mV input)

OK, now I'm a bit lost at this part...

Waveshapers and folders strike me as being really more directed at waveforms/signals that are much more stable and consistent than what a guitar string provides, the idea being that manipulation of a wave, in real time, would add some animation to an otherwise "stagnant" signal.  As well, insomuch as a great many waveshapers rely on diode arrangements to divide incoming signals into components that can be manipulated in some way, it is assumed that the signal has to be above some critical level, and not fall below that.  Unfortunately, guitar strings decay quickly.  One can maintain a constant high level by means of compression and overdrive, but there you've already altered the harmonic content of the signal.

I have one of the Korg PME 40X "Waveshaper" modules, and it's not really much more than a fancy fuzz.  I mean, it does provide different fuzz characters, but they are not dynamically controllable, and not the sort of thing that elicits a "Wow, where has this been all my life?" reaction.

I will be using a guitar as the "signal generator", but my chief interest is trying out a waveshaper it to add some different flavours to the EHX SuperEgo synth pedal I have: This is an upgrade of the old EHX Freeze pedal and can generate an infinitely sustaining drone from whatever note or chord is played into it. It has level controls for the synth and dry outputs, with TONNES of level available (I usually have to keep the wet level at around 3 o'clock for unity with the bypassed signal), so being able to boost it to 7.5v p-p might not be absolutely essential for this purpose..... However, I might want to also use it with direct guitar for some occasional graunchy fuzz nastiness, and I might also like to use it in the FX loop of the Superego so I can have clean guitar alongside waveshaped guitar synth drone, and I'm guessing the synth level control is post-return rather than pre-send so it probably does need to be able to deal with guitar output level signals.

[Eb7+9]

I might want to also use it with direct guitar for some occasional graunchy fuzz nastiness ...

well, uh ... yeah

what I posted above are the parameters needed to get full wavebending action

you might need up to 10vpp of signal to get three full "folds" on each signal lobe ... dun't matter if it's from your guitar or voice
you need to bring the level up to that amount of signal swing if you want what you see produced in the video happen with your source

for a signal with 100mV amplitude that translates into a gain of at least x100
that's LOTS of gain ... (you can/should try)

the other important constraint is how much current the input diode string is going to draw at THOSE signal levels
you need an op-amp that won't sneeze at 10mA output draw ... chances are many op-amps will be ok with this
and still produce an un-distorted wave shape driving the Buchla wave-bender diode network input

but I'm just pointing that out now in case someone runs into problems and wonders why

now, on the flip side, we know this pre-clipping might not necessarily be a bad thing either
but I like to separate the mechanisms in case I want to have control over each later ...

the first idea is to try a version of the circuit where there is no clipping anywhere
(ie., by using a high-gain/high-drive input amplifier)

afterwards, you can try introducing some dynamic curtailment and see what that sounds like
there's quite a bit to experiment with here

as a first try you could use an un-beefed (straight) op-amp driver ...

http://www.lynx.net/~jc/Buchla100hz200mVpp.png

for the  front-end amplifier in the schematic I'm posting you'll want replace the 10k fixed resistor (R18) by a 10k variable one,
providing a DRIVE control
and you'll want to stick a volume pot at the output of the last op-amp,
providing a VOLUME control

[iainpunk]

holy s#it, why haven't i seen this thread before, i have been playing with a wavefolder fuzz on and off for about 5 years now.


i found that using single-fold wave folder bits gives more flexibility and a deeper, more accurate fold. the down side is that you need to stack multiple single fold bits in series to get it to do multiples, but the amount of folds can be up to 1+2ⁿ where n is the number of stages, if designed correctly. a gain of 3 in between stages gives the most accurate folding in my experience
i find that the best sounds are had with single stage wavefolding. also, don't compress it before hand, the playing dynamics have huge effect on the sound, almost like an envelope filter sometimes, which is almost the only thing it has going for it in the conventional sense.
depending on the input amplitude and pre-gain, they can sometimes react extremely poorly to chords, but the amount of pre gain can make the clean signal poke out above the folded waves, making it a bit more like crossover distortion, in this operating mode, chords do work, but youll get a JaMC like fizz in the back ground

i currently have an experimental 2 stage folder on my breadboard, which i am in the process of enhancing for bass use, by making it even more ''''bouncy'''' shaping the EQ both up front and after the folds

ill be happy to answer more questions, or share design concepts and ideas.

cheers

[sergiomr706]

i currently have an experimental 2 stage folder on my breadboard, which i am in the process of enhancing for bass use, by making it even more ''''bouncy'''' shaping the EQ both up front and after the folds

ill be happy to answer more questions, or share design concepts and ideas.

I d really like to see your bass implementation, as a bassplayer myself always keen on playing with these mutated effects. Thanks a lot

[iainpunk]

currently its just a breadboard setup, and i havent physically drawn the circuit yet.
its a simple gain of 16x opamp, followed by two wave folder stages, the first one has red leds and 4148 diodes in series for a higher forward voltage, the second stage has single 4148's. this is then followed by a bridge-T filter which has a wide, shallow scoop around the 560Hz point which basically accentuates the bass's natural low end and the ''bouncing overtones'' while not filling up to much of the mix like bass over drives often do. a cool thing about wave folding is that it retains a part of the input instrument's character. the last thing is an output buffer and volume control.

if i were doing this for a guitar, i'd put in more gain upfront, and add traditional clipping after the wave folding stages to delete some of the guitar's normal character in favour of normal distortion characteristics mixed in with the wave folding character. ow, and i wouldn't scoop the mids, maybe ill even boost the mids.

these aren't what i'd normally do for bass distortions, but it just fits the 'bouncy' nature of wave folding. its a bit of a special case. most of the overtones a wave folder generates are non-harmonic distortion, which sounds, well, different, synth-like, nasty, spunky....
hope this helps a bit
cheers