[sdiy] linearize OTA for VCF?

[jhaible at t-online.de]

> I believe one generally needs to design so that the input 
> structure doesn't 
> clip. 
[...]
> The most conservative approach (when 
> designing a filter with feedback, say) would seem to be 
> to design so the 
> input structure cannot clip until the input signal 
> reaches the rails. 

Why should a module input only clip when its own output,
or the driving module's output, reaches its rails ?
Often, the outputs of modules are opamp-based, and often,
an opamp being driven to its rails does more unpleasant 
things than just limiting the signal. Input clipping,
be it soft clipping from differential pairs or hard
clipping from linearized structures, is *fast* at least,
so you don't get any further unpleasant effects than
cutting off the signal peaks. IMO, the limiting feature
of a synth module's input should be used to prevent the 
module's output from clipping, not the other way round.

JH.