Adding dsp tone control to guitar pedals

mrahc626 · February 2, 2024, 11:17am

I have now made a couple of different audio effects for guitar and bass on the terrarium platform but have never added a tone control to these projects. What type of filtering and over what range is common. By the looks of things, tonestacks in analog pedals tend to employ more complicated filtering than just singular hp or lp filters.

Applications i have in mind which may require different approaches are:

Global tone control for a bass compressor+overdrive project
Tone control for a delay to shape the tonal characters of the echos

Let me know if anyone has any useful resources or tips regarding this design problem

alo.bu · February 12, 2024, 8:23pm

You’re probably looking for a digital low-pass filter. The simplest solution is a one-pole IIR (there’s a DaisySP class for this, I think).

Depending on the sound you’re going for, that filter could be at the output, or in the delay line (so that subsequent echos get progressively damped).

For a more subtle effect (especially in the feedback loop), you could try out a filter with a zero at Nyquist, e.g.

y[n] = 0.5 * (x[n] + x[n-1])

mrahc626 · February 21, 2024, 3:23pm

I’ve since found this which is more in line with what im looking for

https://www.ampbooks.com/mobile/dsp/tonestack/

mrahc626 · February 22, 2024, 2:34pm

For any future people with the same issue, i found these

And this in faust library

github.com

grame-cncm/faustlibraries/blob/master/tonestacks.lib

/**
 **  Guitar tone stacks (based on the work from D.T. Yeh)
 **  some values are taken from CAPS plugin tonestack 
 ** 
 **  this tonestacks.library provide the following tonestack models:
 **  bassman, mesa, twin, princeton, jcm800, jcm2000, jtm45, mlead,
 **  m2199, ac30, ac15, soldano, sovtek, peavey, ibanez, roland, 
 **  ampeg, ampeg_rev, bogner, groove, crunch, fender_blues,
 **  fender_default, fender_deville, gibsen
 **  
 **  USAGE :
 **        _:component("tonestacks.lib").model(t,m,l):_
 **  WHERE :
 **       model is on of the models above.
 **       t is treble freq control in range of (0.0 - 1.0)
 **       m is middle freq control in range of (0.0 - 1.0)
 **       l is low freq control in range of (0.0 - 1.0)
 ** 
 **  EXAMPLE :
 **       process = component("tonestacks.lib").jcm2000(t,m,l)

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tele_player · February 22, 2024, 2:49pm

Did you adapt these to use in pedals with other DaisySP stuff?

mrahc626 · February 22, 2024, 2:50pm

Not yet! idk about the faust one but option one looks doable

mrahc626 · February 22, 2024, 2:51pm

they both are derived from the same research paper so with that and these code examples im sure i can work it out. Perhaps i will share here if i get it working