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

[Michael Zacherl]

On 6.Mar 2014, at 0:27 , Tom Wiltshire <tom at electricdruid.net> wrote:

> 
> On 5 Mar 2014, at 23:08, Michael Zacherl <sdiy-mz01 at blauwurf.info> wrote:
> 
>> 
>> On 5.Mar 2014, at 23:45 , Mattias Rickardsson <mr at analogue.org> wrote:
>> 
>>> Seems almost impossible.
>>> Could it be a major typo? :-)
>> 
>> ;-) 
>> http://www.analoguesystems.co.uk/pdf/RS110.pdf – first page, last paragraph …
>> 
>> m.
> 
> I'm not sure that document makes anything clearer. It says:
> 
> "The RS110 consists of a two channel audio mixer followed by four, parallel, resonant filters with voltage controlled frequency and a unique "insert" point in the feedback path that generates and controls resonance."
> 
> Now, I seriously doubt that there are genuinely four separate, parallel 4-pole filters on that PCB. Although that would be one way to do it, it would be very inefficient. So what exactly *are* they talking about?
> 
> My bet is a simple 4-pole Moog-style ladder (hence the talk of a "discrete" filter with "no filter chips") with several mixers doing pole-mixing to get the various responses (that's the "parallel" part).
> 
> Hasn't anyone on here got one? Can't someone just pull one out of the rack and have a look?!?

I'm not sure if I understand this either: http://www.youtube.com/watch?v=muvN_coN4sE


plus http://vimeo.com/15992747


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