Nasty digital aliasing when using LFO Modulation



  • I'm working on a new project that uses a bunch of LFO's that are modulating filters.

    Every time the filters are modulated it introduces really noisy digital artifacts into the signal making everything sound terrible.

    I'm using Low Shelf EQ, High Shelf EQ, Moog LP, and SVF HP... but have tried all of them and all have the same problem. Some are worse than others but all of them add noticeable unwanted digital aliasing making the plugin sound amateurish.

    I'll put 2 screenshots below of a simple sub-bass loop showing the dry signal, and the wet signal once the modulation is added.

    Notice on the 2nd one all of the added peaks from 500hz upwards. It sounds as if there is a bit crusher added every time the modulation moves anything.

    Is there a way to get around this at all?

    Dry Signal:

    Screen Shot 2019-11-09 at 14.17.15.png

    Wet Signal:

    Screen Shot 2019-11-09 at 14.16.57.png



  • @SteveRiggs Filters in Hise are bad for modulation, except the Ladder and maybe few others (SVF maybe?)



  • Jupp the SVF and Ladder are the only ones that are meant to be modulated.

    I‘ve added some SVF replacements for the biquad filters though (check the filters.sv_eq node) that behaves better when modulated than their biquad counterparts).



  • @Christoph-Hart @ustk That's a big shame. I'll check out the new filters node but I doubt I'll be able to use it with a floating tile for the screen?

    The main things I wanted to modulate were the Low Shelf and High Shelf EQ's in the filter module (but they sound the worst), and the panner, but that also doesn't work when modulated. I was hoping that might get fixed soon so I didn't rule it out just yet. Do you think it will?



  • Well, please try if the svf_eq filter sounds better, they definitely have no zipper noise like the biquad stock filters.

    They are a drop-in replacement, and I've added a preprocessor macro (something like HISE_USE_SVF_FILTERS_FOR_EQ (or something like that) which make the CurveEq module use those instead, from there you have all the filter display possibilities you need.

    The filter modules are still using the old ones, but changing this is trivial (and actually a reasonable request since you might want to modulate these even more than the CurveEq bands).



  • @Christoph-Hart Ok thanks man. I'll rebuild later and try them out.


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