4600/5600 synth: any know more?

[The Dark force of dance]

Y-ellow Y'all.
        I'm kinda curious about the below statement.
        
At 08:24 AM 9/16/97 +1000, Ken Stone wrote:

>It is also HL/LP/BP.  The later version used in the 3600 (LP only, 24db)
>uses two 12 db filters in series. This module has to be my favorite VCF it
>has great roll off, and as far as I am concerned, a good sound.  I have used
>it to drive a sub-woofer before... nothing over about 30 Hz getting though!
>Of note, the control portion of this VCF can be used to drive as many
>filters as required, if a little creative circuit modification is done.

Does this mean that there were several different filter designs for these
synths. I'm curious as I've just gotten hold of a copy of the 4600/3600 data
and it shows the filters to be of a semi-discrete switched capacitor
variety. No resonance feedback and done with cmos bilateral switches. Now
I've got now complaints about the method, I'd often thought of using an SCF
approach, however without resonance they don't scream. If there was a
revised circuit I'd be most interested.

I think it is NSC that make a suitable SCF in a chip that, at a glance I
once pegged as being a prime candidate. Being able to produce a multi-mode
12/18/24 dB/oct filter. Given that some kind of feedback mechanism could be
incorporated, and from memory it seemed likely, one could vary the Q of the
filter at will. Making it likely to make an ideal DCF. Or with the addition
of a VCO as in the case of the 4600 filter, a VCF. However if they have
added a resonance scheme to the 4600 VCF I'd me most interested to learn how
they did it.

Thanks in advance.

Be absolutely ICbeox.
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