I'm designing a distortion circuit :)

[Eternal Dragon]

In spite of what R.G. says (and I know he was tinkering with music electronics well before I was even born) I think it should be possible to use the diode waveshaper in the feedback path of an op-amp to make something vaguely like what the original poster wanted.

By just hooking the thing into the feedback path, the gain will be:

Infinity for small signals when no diodes conduct (sounds about right for crazy metalhead, in practice would have to be reduced by a high value shunt resistor)

Zero for large signals when the dual series diode strings conduct (to give the flat top to the waveform)

Some value of your choice for signals between one and two diode drops, when the single diode pair with resistor conducts (to get the sort of triangle-y looking parts)

By replacing the dual diode strings with that transistor/pot "Rubber diode" circuit, you could make the flat top adjustable in a similar way to what the OP wanted. Or split the waveshaper across two op-amps with a gain control in between to do the adjustment.

FWIW, my favourite solid-state clipping circuit so far is a rubber diode made with a MOSFET instead of a regular transistor. It ends up giving a smooth squashing of the waveform that's almost more compression than clipping.

I'll look into that .


I've also been thinking of old fourier and the fact that any wave can be broken up into a sum of sin waves. Anyone done any FX with that sorta stuff?? I can do fourier/laplace transforms and all that but I have no idea how to make circuits out of the equations or anything. Yer, just having a look at my options at this point :P

[Eternal Dragon]

I think it should be possible to use the diode waveshaper in the feedback path of an op-amp to make something vaguely like what the original poster wanted.

Ohhhh I get what you're saying now. Thats a superdiode . So when you do it this way it will be close to ideal hence it wont have those soft corners. I've had a look into 3 segment diode waveshapers used to turn triangle waves into sin waves for signal generators, and I guess if I used superdiodes in a similar fashion then I could get those harsh edges.

If only I had thought of superdiodes at the beginning

[Avrum]

Fourier analysis and additive synthesis is usually the domain of digital signal processing (look up the phase vocoder for doing time stretching and pitch shifting). But a vocoder is the simplest analog implementation by sampling the energies in various frequency bins (with a filter bank) and then applying those values to VCFs (preferably driven by a richly harmonic or noise source) or VCOs.

As for laplace transforms, those will help you design filters by allowing you to go back and froth between the time domain (to look at transients and impulse responses) and the frequency domain (to look at the frequency response and the transfer function).

If you want to know how your ideal distortion circuit you described above will sound at an ideal frequency in comparison to a square wave at the same frequency, you could take the fourier transform of your square wave and add it to the fourier transform of your triangular wave...assuming of course the system is linear and time invariant and the signals are infinitely periodic. This will show you what you'd hear, but it's probably just as easy (and more sonically discernable) to add the two signals and listen to it in some software application like adobe audition or matlab...or even an analog synthesizer that can sync its oscillators. Though in this ideal case, I doubt you'll get the metal sound you're looking for.

I'll look into that .


I've also been thinking of old fourier and the fact that any wave can be broken up into a sum of sin waves. Anyone done any FX with that sorta stuff?? I can do fourier/laplace transforms and all that but I have no idea how to make circuits out of the equations or anything. Yer, just having a look at my options at this point :P