[sdiy] Multi-output comb filter?

Corey K coreyker at gmail.com
Tue May 22 07:04:25 CEST 2018


Option 2: write out the Z-transform for your comb filter. There will be one
pole per peak, and these will be spaced at equal angles around a circle in
the complex place. Add a zero to perfectly cancel the pole corresponding to
the peak you want removed. This will in turn correspond to an FIR filter
that you can run before or after your comb filter.


On Mon, May 21, 2018, 21:54 cheater00 cheater00 <cheater00 at gmail.com> wrote:

> Good idea, but that's still going to pass some of it through. I meant
> a perfect removal.
>
> On Tue, May 22, 2018 at 6:52 AM, Corey K <coreyker at gmail.com> wrote:
> > Easiest way: place a high pass filter in series with your comb filter.
> >
> > On Mon, May 21, 2018, 21:15 cheater00 cheater00 <cheater00 at gmail.com>
> wrote:
> >>
> >> Is it possible to build a delay based comb filter that's missing the
> >> first peak? I.e. say we have a comb filter at 1 Hz, with peaks every 1
> >> Hz, is it possible to also have a comb filter at 2 Hz with peaks every
> >> 1 Hz - perhaps using multiple delays? I know when you synthesize
> >> waveforms using DSF ("discrete summation formula") synthesis, you can
> >> create a waveform at any base frequency, with the partials spaced by
> >> any constant amount of Hz, but I'm not sure how this would be done
> >> with a delay based comb filter. Note, I'm talking about synthesizing
> >> this in digital.
> >>
> >> On Mon, May 21, 2018 at 4:45 PM, Tom Wiltshire <tom at electricdruid.net>
> >> wrote:
> >> >
> >> >
> >> >> On 21 May 2018, at 11:24, Ingo Debus <igg.debus at gmail.com> wrote:
> >> >>
> >> >>
> >> >>> Am 21.05.2018 um 06:24 schrieb rsdio at audiobanshee.com:
> >> >>>
> >> >>> You’ll get a lot further realizing that a comb filter has only a
> >> >>> single input and a single output, where the constructive and
> destructive
> >> >>> interference ends up favoring some frequencies and penalizing
> others.
> >> >>
> >> >> What if you use a multi-tap delay?
> >> >
> >> > You’ll still get constructive and destructive interference that ends
> up
> >> > favoring some frequencies and penalizing others. With *many* taps (or
> >> > delays)  you could build a specific frequency response, but you’re
> basically
> >> > building an FIR filter by analog means, and it wouldn’t be cheap or
> simple.
> >> >
> >> >
> >> > _______________________________________________
> >> > Synth-diy mailing list
> >> > Synth-diy at synth-diy.org
> >> > http://synth-diy.org/mailman/listinfo/synth-diy
> >>
> >> _______________________________________________
> >> Synth-diy mailing list
> >> Synth-diy at synth-diy.org
> >> http://synth-diy.org/mailman/listinfo/synth-diy
>
-------------- next part --------------
   Option 2: write out the Z-transform for your comb filter. There will be
   one pole per peak, and these will be spaced at equal angles around a
   circle in the complex place. Add a zero to perfectly cancel the pole
   corresponding to the peak you want removed. This will in turn
   correspond to an FIR filter that you can run before or after your comb
   filter.

   On Mon, May 21, 2018, 21:54 cheater00 cheater00
   <[1]cheater00 at gmail.com> wrote:

     Good idea, but that's still going to pass some of it through. I
     meant
     a perfect removal.
     On Tue, May 22, 2018 at 6:52 AM, Corey K <[2]coreyker at gmail.com>
     wrote:
     > Easiest way: place a high pass filter in series with your comb
     filter.
     >
     > On Mon, May 21, 2018, 21:15 cheater00 cheater00
     <[3]cheater00 at gmail.com> wrote:
     >>
     >> Is it possible to build a delay based comb filter that's missing
     the
     >> first peak? I.e. say we have a comb filter at 1 Hz, with peaks
     every 1
     >> Hz, is it possible to also have a comb filter at 2 Hz with peaks
     every
     >> 1 Hz - perhaps using multiple delays? I know when you synthesize
     >> waveforms using DSF ("discrete summation formula") synthesis, you
     can
     >> create a waveform at any base frequency, with the partials spaced
     by
     >> any constant amount of Hz, but I'm not sure how this would be
     done
     >> with a delay based comb filter. Note, I'm talking about
     synthesizing
     >> this in digital.
     >>
     >> On Mon, May 21, 2018 at 4:45 PM, Tom Wiltshire
     <[4]tom at electricdruid.net>
     >> wrote:
     >> >
     >> >
     >> >> On 21 May 2018, at 11:24, Ingo Debus <[5]igg.debus at gmail.com>
     wrote:
     >> >>
     >> >>
     >> >>> Am 21.05.2018 um 06:24 schrieb [6]rsdio at audiobanshee.com:
     >> >>>
     >> >>> Youâll get a lot further realizing that a comb filter has
     only a
     >> >>> single input and a single output, where the constructive and
     destructive
     >> >>> interference ends up favoring some frequencies and penalizing
     others.
     >> >>
     >> >> What if you use a multi-tap delay?
     >> >
     >> > Youâll still get constructive and destructive interference that
     ends up
     >> > favoring some frequencies and penalizing others. With *many*
     taps (or
     >> > delays)Â  you could build a specific frequency response, but
     youâre basically
     >> > building an FIR filter by analog means, and it wouldnât be
     cheap or simple.
     >> >
     >> >
     >> > _______________________________________________
     >> > Synth-diy mailing list
     >> > [7]Synth-diy at synth-diy.org
     >> > [8]http://synth-diy.org/mailman/listinfo/synth-diy
     >>
     >> _______________________________________________
     >> Synth-diy mailing list
     >> [9]Synth-diy at synth-diy.org
     >> [10]http://synth-diy.org/mailman/listinfo/synth-diy

References

   1. mailto:cheater00 at gmail.com
   2. mailto:coreyker at gmail.com
   3. mailto:cheater00 at gmail.com
   4. mailto:tom at electricdruid.net
   5. mailto:igg.debus at gmail.com
   6. mailto:rsdio at audiobanshee.com
   7. mailto:Synth-diy at synth-diy.org
   8. http://synth-diy.org/mailman/listinfo/synth-diy
   9. mailto:Synth-diy at synth-diy.org
  10. http://synth-diy.org/mailman/listinfo/synth-diy


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