AS3109 VCF

Description

The AS3109 chip is Alfa’s modern equivalent of the famous Roland IR3109 filter chip, as used in the Jupiter 8 and SH-101, amongst others. It’s a classic. It has four independent OTA+Buffer sections, all controlled from a single exponential current source. The sections can be configured to build all the standard filter types, Lowpass, Highpass, Bandpass. It can even do Allpass. It’s the chip in the Boss PH-2 12-stage “Super Phaser”.

Note that it doesn’t include any provision for resonance control on the chip (like the similar SSM2040)  so you have to do that with external circuitry, either a VCA or a simple pot. There’s a page over in the Articles section with lots of details about Roland’s original synth filter designs using the IR3109.

Download Alfa AS3109 4-pole VCF datasheet

These are brand new chips fresh from the Alfa Rpar semiconductor factory in Riga, Latvia.