[sdiy] HPFs and ADSRs

[Antti Huovilainen]

On Sun, 6 Jun 2010, Aaron Lanterman wrote:

> By first version, do you mean the Korg-35 IC version, and by second 
> version, do you mean the LM13600 based version?

Yes.

> That second version can be understood that way - it gives insight into 
> how it works - but it does look like a "Bach" version of a Sallen-Key 
> (where there are two buffers instead of one) to me. At least that's what 
> I've been calling it in lecture, and giving homework assignments on... 
> :)

Yes, it is the same as the "Bach" filter (for one particular resonance 
setting). However, nowhere on that page does it say anything about the 
"Bach" being a version of Sallen-Key. I don't consider it one either as 
the design equations are different, and the filter even works differently 
(as Sallen-Key is not two identical RC sections in series).

Antti

"No boom today. Boom tomorrow. There's always a boom tomorrow"
   -- Lt. Cmdr. Ivanova