[sdiy] Replicating a Wah spectral response with DSP and 0-5vdc pot control ??

[rburnett at richieburnett.co.uk]

It can surely be done JP. Some examples of the "bandpass" frequency 
responses of the Cry Baby are already on the Electrosmash website. The Q 
factor changes with frequency and the filter resonance becomes sharper 
as the frequency is swept lower. This is a bit unusual and will surely 
be a defining characteristic to the Cry Baby sound. There's other bits 
of filtering going on too which will also shape the tone. So don't 
expect a textbook state variable filter to get you that sound without 
some tweaking. There's also potential non-linear behaviour that Andy 
mentioned if you drive it hard enough.

As for cost, I'd say developement wouldnt cost much in dollars but will 
take considerable time tweaking algorithms and doing side by side 
comparisons of the sound. Things like ARM Cortex dev boards and tools 
are dead cheap these days.

If you actually intend to do this, and make your own DSP guitar pedal, I 
think one of the hardest parts will actually be getting the noise floor 
low enough and free of any unwanted tones that it can be used anywhere 
in a guitarists signal chain. It doesn't take much "block processing 
whine" to be unusable ahead of a high gain distortion pedal!!!  But then 
the Wah effect is so simple you could probably get away with just 
processing one sample at a time.

I'd start by writing some C code to do some offline processing of a few 
WAV files and see how close you can get to that iconic Wah sound.

-Richie.


On 2024-07-01 01:09, Jean-Pierre Desrochers via Synth-diy wrote:
> Just a thought tonight..
> 
> Would it be difficult to use some kind of DSP to replicate
> the adjustable band pass frequency effect of a specific Wah Wah brand
> I would be controled by a simple 0 to 5vdc linear pot control ?
> No more scratches nor induced HUM in the normaly used inductor
> in such a design.. ?
> 
> That could be a very interesting design to use
> For many guitar players like me..
> I don't have the skills to do such DSP programing,
> but I'd like to know if it would be an expensive project
> (R and D speaking).
> 
> 
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