Most interesting, versatile diode clipper/ waveshaper in distortion pedal?

[Vivek]

Most AIAB, distinction pedals seems to be content with back to back diodes

Either in feedback loop

Or shunted to ground

Or both

What's the most interesting, innovative, versatile diode clipper/ waveshaper in an AIAB or distortion pedal that you ever saw?

[teemuk]

Pritchard has presented very interesting waveshaping circuits and I'd also rank those clipping circuits with dynamically modulated threshold quite high in my personal list (diodes or without). i.e. ADA "D-Torsion" cell is principally just a "rubber zener" but its tweakability with additional control signals is very clever.

[Vivek]

Pritchard is great !

His patents are recommended reading for all.

[Vivek]

Didn't some Crate amps have modulated Rubber Zeners ?

[Vivek]

I'm in touch with a Researcher Dr. Buffa.

He posted a web site with audio going through a bezier transfer function with the bezier parameters modulated by the input signal's envelope.

I'll re - find that link and post here.

[Vivek]

https://output.jsbin.com/zotaver

Dynamic clipping characteristics based on signal envelope

[Mark Hammer]

Most AIAB, distinction pedals seems to be content with back to back diodes

Either in feedback loop

Or shunted to ground

Or both

What's the most interesting, innovative, versatile diode clipper/ waveshaper in an AIAB or distortion pedal that you ever saw?

It depends on what one is trying to achieve: a ferocious-all-the-time tone, or something that is pretty clean until you dig in.  The two objectives require different approaches.  Diode-based clipping has the challenge of depending on headroom limits, which are largely fixed, rather than gradated/gradual.

Diodes to ground will conduct partly based on the current fed to them.  This makes the current-limiting resistor in series with the signal of relevance.  Varying it dynamically might be able to do something of interest, but I can't confirm that.

[Vivek]

David Tarnowski, ADA "D-Torsion" clipping cell:
https://www.google.com/patents/US20130077801

Dirk Baldringer, Dual Drive clipping cell:
https://www.google.com/patents/US20090231011

[Vivek]

https://drtube.com/schematics/musicman/gb2.gif

Well-known circuit that has been posted here often

Rubber diodes used as clippers.

However these are not modulated.

I request someone to post link to schematic of modulated Rubber diodes.

[soggybag]

This has been on my mind since it was posted many years ago.

https://www.diystompboxes.com/smfforum/index.php?topic=36572.0

I think the issue with this circuit is that it needs to be driven at a higher voltage than you find in stompboxes.

[soggybag]

This is another one. If I understand it it clips just the high frequencies.

https://www.diystompboxes.com/smfforum/index.php?topic=22113.0

[Vivek]

another golden oldie... (US2890832)

Arbitrary function generators for synthesising functions by piecewise approximation

[Rob Strand]

Arbitrary function generators for synthesising functions by piecewise approximation

A widely quoted one is,

A.E.Crump, "Diode Function Generators", Wireless World, Dec 1967, p594 to p598

https://worldradiohistory.com/UK/Wireless-World/60s/Wireless-World-1967-12.pdf

It's about generating non-linear transfer functions using diodes.   (Not signal generators)

[Vivek]

It depends on what one is trying to achieve: a ferocious-all-the-time tone, or something that is pretty clean until you dig in.  The two objectives require different approaches.

Please please please teach me how to design circuits that are pretty clean until you dig in.

ie increase the difference of sound between :

signals below a particular level
and
signals above a particular level ?

Has anyone tried to clip "V(input)^2" in an attempt to make distortion exponential for higher signals while quite clean for lower signals ?

Or is piecemeal transfer function design the answer ?

or multiple stage clipping  ?

[Vivek]

Here is an interesting circuit from the esteemed Bernie Hutchins.

This looks interesting !! First time I saw diodes between inverting input and signal. I suppose it has 1/x corellation with gain so should really make things interesting when it kicks in.

I will try on SPICE first.

[11-90-an]

Try it on breadboard, i think...

[GibsonGM]

Sounds samples, please!

[Mark Hammer]

Please please please teach me how to design circuits that are pretty clean until you dig in.

I wish I knew.
Probably the closest we've gotten to it is the basic Fuzz Face design, which cleans up nicely at a lower input signal.

[Steben]

Saggy power amp at the edge of break up. This involves a complex reaction to the input signal amplitude. The way peavey transtube t dynamics does it or quilter is probably potential pedal material. They add dynamic crossover distortion so typical for those tube amps with solid state tech. This means with the same input dynamics you add more harmonics and compression than only clippers would. This makes for a bigger range between clean and dirt with the same input range.

A fuzz face is indeed a very nice gem of a circuit with an extreme simplicity yet it does react more to the volume control rather than just dynamics.

[amptramp]

I have one homemade pedal called Here Come the Fuzz that uses active diode clamp elements that act like a diode with only a few millivolts between complete signal passage and complete clipping.  This is my much-modified original schematic (and there may be more mods coming):



IC's 2A and 2B in the middle of the circuit act as ideal diodes because they have diodes included inside the feedback loop of an op amp.  These diodes have extremely sharp breakover from no conduction to full conduction in less than a millivolt.  They are each coupled to the circuit by a couple of pots that set the diode resistance and there is a rotary switch that selects coupling of the diodes to the T junction of a pair of 10K resistors.  They can be switched in directly or through capacitors or a series L-C network.  I may start a thread about it if anyone is interested.  As for versatile, look no further, this is it.