[sdiy] Matrix12 CEM3372 trick and CEM3396 question

[Rainer Buchty]

On Wed, 3 Oct 2007, Dave Manley wrote:

> You could also use this method to completely defeat the internal LPF 
> and instead use an external filter (or other signal processor).  Take 
> the signal off the first stage cap pin to whatever external filter you 
> want, set the filter cutoff so that the internal LPF contributes 
> nothing to the VCA, and then couple the external filter output in via 
> the Gain Set pin.

Yes, but the idea was to use the filter's partial signals to sum them up 
in a way the Xpander did to reach filter types other than LPF. If you 
mute the LPF, then the partial sums will become zero as well.

Although, I wonder: would it be possible to tap cell 4 (given the 
SSM2040 as a prototype, the cap is between the OTA and the buffer), 
invert it and sum *that* signal together with the externally generated 
filter signal, then feed it into the VCA gain?

Rainer