Distinct distortion

[FiveseveN]

Wise denizens of the Internets, I seek your aid!
Trying to make a(nother) pedal with lots of different flavors of distortion and I still have a couple of slots left. Here's what I've come up with so far:
• classic op amp diode clipper (RAT, Crunch Box)
• maybe op amp "soft clipper" (Tube Screamer)
• LM386 (Distortus Maximus, Acapulco Gold etc.)
• cascaded CMOS (Red Llama)
• Superfuzz
• comparator fuzz

Now I'm really struggling to find other options that are distinct enough but still generally useful, e.g. crossover and wavefolding are probably too niche. I know filtering plays a major role in a distortion's character and that's kind of the issue: there's only so many ways to chop up a signal. But I'm sure there's plenty I've missed.
Also wasn't there a similar thread some many years ago?

[Mark Hammer]

Don't dismiss crossover distortion so quickly.  The old Gretsch Contrafuzz was an interesting little circuit that could be tweaked to produce en emerging fuzz (hence the name), that started out clean and got fuzzier as the note  lasted longer.  It did this by cranking the daylights out of the signal and clipping it hard enough that it would still be fuzzing long after a clean copy of the input had decayed and faded out.

Looking over the circuit, I noted that the clipped signal was seriously attenuated by R6 and VR1.  Inspired by the Boss HM-2, I got curious about incorporating some crossover distortion, so I added the pair of series Ge diodes and variable series resistance to provide some crossover distortion that could be added in when the resistance in series with those Ge diodes is reduced.  So the circuit shown here lets me blend in clipping and crossover distortion, in varying amounts.  The original Contrafuzz has fixed gain, but I added a variable gain control

I have to say that Xover distortion LOVES bridge pickups.  This isn't the greatest video demo, but it demonstrates the audible difference between clipping and crossover distortion.  Since the video is grainy, controls, clockwise from lower left are: master output volume, Gain, Xover amount, Xover+clipping distortion amount.  Because the Xover diodes have a lower forward voltage than the 1N4401 clipping pair, it is technically possible to dial back the gain enough to get mostly Xover.  Swap the Ge pair for Schottkys and you can probably get *only* Xover if you wanted and set the Gain just right.

I will also direct your attention to the soft distortion circuit in the Roland Funny Cat.  It makes clever use of envelope ripple from a poor rectifier circuit.  The soft distortion subcircuit is everything from C1 through to C5.  The gain of that op-amp is dictated by the 470k feedback resistor, and whatever the drain-source resistance of Q1 happens to be at any given moment.  The output of the op-amp feeds the gate of Q1 via R5/D1.  The other components dictate how "strict" and smooth the rectification of the op-amp's output is.  Because it has very little ripple rejection, it turns Q1 on and off very fast, at audio frequencies, yielding an interesting and very distinctive kind of distortion.  Between R7 and the SDS level control, whenever Q1's resistance is high, and the op-amp's gain is well below 5x, the circuit almost provides a kind of noise gate function; i.e., it's quiet until you start picking.

I find it a really interesting and overlooked effect/circuit.  I'm surprised no one has resurrected it.

[Rob Strand]

A good MK1 Tone Bender never goes a miss.

13:00
https://www.youtube.com/watch?v=SkzHNpQ7QCA

[marcelomd]

Cascaded MOSFETs (Box of Rock)
Cascaded JFETs (several MiaBs)
Cascaded BJTs (Big Muff)
Cascade all the things!

[idy]

octave fuzz can be added to any of those.

[jafo]

Try modulation to control the distortion: its depth, its onset, its intensity, its duration, etc. (Think of it as an analogy to tremolo, wherein an oscillator modulates volume.) Synth guys do this all the time; why should they (err, we) have all the fun?

[CheapPedalCollector]

Sziklai fuzz (I'm unaware of anyone doing this yet)
Darlington fuzz (DOD Sustainer/Attacker)
Axis style fuzz
Harmonic Percolator style fuzz

With and without clipping, they give vastly different sounds.

The old Morley power fuzz circuit is an interesting one too, the latter big boy edition with the feedback diodes is a particular favorite.

[Steben]

I still think the Bluesbreaker is the best bandwagon soft clipper ever. Perhaps simply because of the way it works with its variable hardness of the clipping according to the gain. Brilliant.

[ElectricDruid]

A transistor differential pair for soft clipping hasn't been mentioned yet. Whether it's sufficiently different from things that already are on the list, I couldn't say. Nice for a soft drive sound though.

Ultimately, I'd say four or five options are enough. You want some soft overdrive type sounds, and some crunchy sounds, and some harder distortion sounds. Four or five basic distortion mechanisms ought to cover that. After that, it's down to gain and drive levels and tone shaping (and you've got almost infinite variety there!). There's a serious danger of trying to cover everything and just building something that is too much and too complicated - unless this is purely a personal experiment, in which case, go ahead and add as many different types as you like.

A lot of the best gear is good because it simplifies things and limits the controls to the important parts of the range. As experimenters, we often tend to push things ("How about if I make this LFO go up to 20Hz?", "It might be cool to increase the gain on this overdrive..." etcetc) but actually, it's nice a lot of the time to have fairly constrained limits to work within. Those limits define the "sound" of a given pedal and if the pedal is any good, they cover all the best stuff it can do. I'm not really against limitations. I think often they're quite inspiring to push against!


 

[jafo]

Yeah, we've pretty much exhausted the possibilities for clipping to either rails or P/N junctions; differential is still relatively fresh, though.

We've also had AM modulation exhausted for decades.

Could we use a frequency multiplier on an audio input? That would let us explore FM synthesis territory. It would also let us build analog exciters easily. I'd imagine an expression pedal would be ideal to control the modulation.

Would a Chebyshev filter work on a guitar signal? That gives us static harmonic distortion (or waveshaping, really).

[Fat Bob]

Someone was talking about the MXR switched cap filter and said slowing the clock down
would create distortion. So you could digitize the signal and modulate the clock for a new
kind of distortion. I guess it is similar to Bitcrushing...