[sdiy] Matrix12 CEM3372 trick and CEM3396 question

[Dave Manley]

>>> Checking the trick used in the Matrix12 with the CEM3372 (to use a
>>> 4051 mux and R network to produce LP, BP and HP with the 4 cells of
>>> the VCF), I was wondering if the same trick could be achieved with the
>>> CEM3396 ?

>> AFAIK basically yes, but mind you that the CEM3396 has no dedicated VCA
>> input like the CEM3372; hence, if you do the trick you can't feed the
>> sum signal back into the CEM3396 but rather need an external mixer.

The last paragraph of the CEM3396 datasheet gives a method of coupling 
an external signal into the VCA by using the VCA Gain Set pin.  This 
effectively parallels the internal LPF with whatever you do externally.

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.


-Dave