Now, the standard Shruthi-1 kit comes with the SMR-4 filter board, which, when you look at the schematic, is basically the same design as the IR3109 chip! There are some differences, but for the most part they are the same. There is a mod that can be done (a couple resistor changes and a couple diodes added) that gives it an almost identical sound to the IR3109. Actually, there is a new replacement for the Juno 106 80017A (which was a board that had an SMT version of the IR3109 and some other stuff encased in black epoxy) which uses the same 31700 Op Amp!
But, the problem is, when someone hears the IR3109, it's typically in a polyphonic scenario. Well, I just finished a build for a customer that has 6 SMR-4 voice cards! I decided to set it up like a Juno and see exactly how close it is.
Osc 1: Saw
Osc 2: Off
Sub Osc: about half way
LFO 1 Triangle (sloow) > Osc 1 (very little)
Filter Cutoff about half
Filter Resonance about half
Filter Cutoff > Envelope 1 about 2/3's
Then I run it through a chorus pedal to give it that "Juno" sound. Finally a little reverb.