[sdiy] Gain staging in 4-pole VCFs

Tom Bugs admin at bugbrand.co.uk
Fri Nov 9 12:43:55 CET 2018


I remember reading David Dixon's mention and think I found it: 
http://synth-diy.org/pipermail/synth-diy/2010-October/028382.html
Interestingly he states a gain of 1.414 - whereas Tony's doc gives 1.47

Best, Tom


On 09/11/2018 09:51, Neil Johnson wrote:
> Hi,
>
> Rutger Vlek wrote:
>> I just remembered something I read years ago on the Oakley sound website regarding gain staging inside filters (usually those with >2 poles). It was regarding the COTA filter (cascaded OTA), where Tony only briefly explains using integrators with varying amounts of gain throughout the filter. Hereby (I presume) generating a very smooth combined saturation curve, where each stage contributes its share (much like guitar distortion pedals with several stages of saturation involved). He refers to a famous filter that inspired him for doing this, and I'm curious which one (the design choice sounds like one Dave Rossum would make...). Also, I'm curious which other filters use this approach.
> I guess you're referring to this document, on page 15:
>    http://www.oakleysound.com/cota2-bg.pdf
> or the earlier version 1 on page 13:
>    http://www.oakleysound.com/cota1-doc.pdf
>
> Neil

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