Yamaha IG000156, vcf

Hi!

The first synthesizer I ever used was a Yamaha CS-10 (or perhaps CS-15). Recently I looked at the specs and noticed that the filter is a Yamaha 16 legged DIP circuit named IG000156, which seems to be used in several Yamaha models from the 70’s . I googled the part without success, I only found a reference to the CS-15 service manual that indicates that the LP-mode has a 12 dB slope which might indicate that it is a 2-pole internal construction? I’m curious, does anyone know anything more about this filter circuit? :slight_smile:

http://synthark.com/synthesizer-museum/yamaha-gallery/conventional/architecture/filter/
http://www.gearslutz.com/board/attachments/electronic-music-instruments-electronic-music-production/349297d1371178553-yamaha-cs-15-filter-problem-yamaha-cs-15-service-manual.zip

falfa

Given that the IC has LP/HP/BP outputs, and only two caps, it looks like it is a SVF. Maybe you can try breadboarding this or TubeOhm’s upcoming thing, and tweak the gains / non-linearities to give it the character of the CS-15?

Thank you! :slight_smile:

I also found a document with Yamaha circuit documentation, the IG000156 is described on page 37:

http://www.loscha.com/scans/Yamaha_IC_Data_Book.pdf

The Block & Schematic diagram looks similar to the description of the Shruthi SVF here:

http://mutable-instruments.net/static/documentation/svf_analysis.pdf