[sdiy] Good 24db/oct HP-LP-BP-Notch filter Schematics ??

[Tom Wiltshire]

On 6 Mar 2014, at 06:34, Andrew Simper <andy at cytomic.com> wrote:

> On 6 March 2014 02:40,  <blacet at blacet.com> wrote:
>> As far as I know, the state variable filter design is the only one that
>> has simultaneous outputs as you require. This is a 12dB design with two
>> stages, although with enough feedback/Q, the apparent slope is much
>> greater.
> 
> You can make 4 pole SVFs that contain 4 integrator stages and produce
> H4 L4 H1L3 H2L2 H3L1, and you can then sum and difference H4 and L4 to
> create allpass and notch.

Do you have any references for that, Andrew? I'd like to see how that's done. I've tried searches for "4-pole SVF" but can't find much.

In summary then, the RS110 is either:

1) A 4-pole SVF design

2) A 4-pole LPF with pole-mixing providing simultaneous outputs

Thanks,
Tom