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

[rburnett at richieburnett.co.uk]

To be honest, I think you could probably get reasonably close to 
modelling the Cry Baby's response with an analogue (op-amp) State 
Variable Filter where only the resistor in the first integrator stage is 
made variable.  This would get you the desired Q variation with cutoff 
frequency.  (Normally the resistors in both integrators are varied 
together to sweep the frequency whilst maintaining a constant Q factor.) 
  I spent some time looking at this a while back, and seem to remember 
that you'd take the output mostly from the LP output of the SVF with a 
little bit of the BP output mixed in too.

This different topology obviously wouldn't model the non-linearities 
inherent in the original Dunlop design, but should get the small-signal 
steady-state response close.  And it shouldn't pick up hum because it 
doesn't use an inductor!  Who knows, it might even sound better than a 
vintage Dunlop Cry Baby! :-O

-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
> that 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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