[sdiy] Shruthi 4PM (was re something else...)

[David G Dixon]

> The same design, without the fancy pole-mixing, is used in my 
> Eurorack module Ripples, and it looks like people are quite 
> happy with it. I also use it on the Ambika (the "4P" 
> voicecard) - this gives a well-behaved, low-part count 4-pole filter.

And I'm presuming that it is very similar to the Intellijel Dr. Octature and
the STG Mankato, all 2164-driven 4PFs based on the same basic topology, and
all well-loved by their owners.