SVF filter tuning


I’ve got my hands on 2 Shruthis and 3 filter boards and am having trouble tuning the SVF. The filter just seems to be way too high - getting the digital noise etc but at lowish settings for cutoff (70-80ish) and filter won’t close. I have SVF chosen in filter type and have tried to change the settings on the various trimmers to no avail. I haven’t got past filter 1 yet - it seems to be pretty in tune with itself, just too high, and I can’t get the range setting down enough to avoid the noise at higher settings. I didn’t build the boards - I can’t rule out build error but does this sound like a common problem? I have read through some of the archives and believe I’m following the correct procedure for filter calibration.


Looks like a build error… Check all parts around IC4.

Will do and thank you for being so attentive on this forum.

Think I got it sorted but I have to double check. Stay tuned if you are at all interested.

Curious on your resolution. Just picked up an Ambika with SVF boards and can also hear digital noise (much more than Shruthi XT with 4PM). In fact not only noise, but the waveforms don’t sound the same as the Shruthi, sounds like more digital artifacts and possible phasing. The 4 voices are consistent, which was what had me fooled. Now I have the Shruthi and the sound is completely different. And it’s NOT the filters.

I got side tracked but one problem I had was to do with proper connection of the filter and control boards. I think that fixed most of the problems although the SVF always seemed a little weird to me. I have tried 2 boards now so I don’t think it’s user error although I haven’t explored it in great detail. Might get to it this week.