Filters from the dsp node section
  • When looking for filters in Audulus, you've probably noticed these filter nodes from the dsp section, but they are a bit odd with no resonance control and an alpha setting instead of cutoff frequency. Why using them, when there is a filter with resonnance and cutoff control in the fx section, and even better a full filter module in the library? They are all 12 dB/oct filters, so what?

    Actually, the filters from the dsp section are not 12 dB/oct but 6 dB/oct (1 pole). That explains why these filters have no resonance control, they are non resonant filters by definition. 6 dB/oct filters are extremely useful for tone shaping, wave shaping or as a slew limiter. Indeed, the lp node from the dsp section is identical to the slew limiter module from the library, but it can work at audio rate and the module can not.

    As for the alpha setting, I think I found the formula to convert it to a cutoff frequency. Attached to this post is a converter that you can use to get the frequency you're looking for. Then you can delete the converter from your patch (cpu saving).
    alpha-frequency converter.audulus
    9K
  • I think it might be worth noting that the slew limiter in the library will provide a linear response, but the LowPass node gives a pleasing log/exp response.image
    Screen Shot 2017-04-10 at 8.44.09 AM.png
    958 x 629 - 74K
  • @RobertSyrett - yes, but the slew modes go between equal slew time between each note no matter how far apart they are to more slew time the farther away the notes are.
  • @biminiroad ahh, I did wonder what that mode button was for.
  • @RobertSyrett - yeah, the "more slew for farther apart" is how analog ones work I think? You'll notice it a lot when doing octave jumps, especially 2 octaves apart.

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