Orgon Systems Mulitmode Filter

[Hugo Haesaert]

Hi Juergen n All !

Digisound 80_7 is a dual state-variable filter module, switched to 
give two and four pole lp-hp-bp  and two pole notch .  The original 
design, as published in ETI and in the ZIP at Anders site uses the 
ssm2040 for it's poles and 13600 for vc resonance .  Subsequently 
(after ssm's demise ?) an 80_7a was designed, using the cem3320 iso 
ssm2040 .  Both circuits can also be found in Barry Klein's book .  
(does anyone have the pcb layout for that 80_7a ?)

Problem (? :) ) with these is that the 4 transconductance cells get 
their current from one source, precluding easy spreading of corner 
frequencies of the BP's, also combining BP+LP (not implemented here) 
would be more interesting .  

The Synton Syrinx filter combinations of three cem3350's (dual state 
variables, independent freq control) look (and sound) very special .  
Don't know wether a full description of this is available on the 
internet ?

Cheers .


Keep 'em oscillating :)

Hugo
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