Filter FM and sideband overload

>Am Montag, 1. Februar 2016 15:23:12 UTC+1 schrieb Steve Pope:
>> SG wrote:
>> 
>> >I've already said the things I *can* say given the information you
>> >gave:
>> 
>> >(1) You're not supposed to change the filter parameters that quickly.
>> 
>> "Not supposed to" according to who?
>
>Me.
>
>> OP stated this is a requirement, that it works in analog, and
>> that there are existence proofs that it works in digital.
>
>That's why I've been suggesting oversampling twice already. With
>enough oversampling the rate of change of the cutoff parameter
>measured in sample periods can be made arbitrarily small and I believe
>that's what's important to keep this time-varying filter stable.
>
>S0lo, please try oversampling. By oversampling I basically mean that
>you operate at a much higher sampling rate internally but try to keep
>the bandwidth of the signals you deal with more limited. For example:
>Operate at a sampling rate of 192 kHz but make sure that your
>sawtooth signal you feed into the filter is band-limited (no harmonics
>above, say, 30 kHz. And after the time-varying filter you might need
>to lowpass the result again to remove inaudible harmonics that could
>get you into trouble during the next nonlinear processing step (if
>there is any).
>
>If your current sawtooth generating code suffers from aliasing, try
>looking for how to create band-limited steps (BLEPs) and compose your
>waveform out of ramps and these BLEPs. Oversampling is also very
>convenient here because it allows you to to keep the BLEP rather
>short. With oversampling you have more "headroom" in the upper
>frequencies where the step response does not have to be good or even
>alias-free. For example, with 2X oversampling you can approximate a
>band-limited step well with just 8 samples. You could create an
>8x64 BLEP table for 64 sub-sample positions of the step.
>
>Cheers!
>sg

Thanks, I've already tried oversampling as I said before, same problem,
may be I'll do that again making sure that I've done it right. I also just
tried a real sampling rate of 192Khz. Same thing, no improvement.

Yes I'm using MinBLEP for the saw tooth, no aliasing at all, super clean
even at 20Khz
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