IR3109 shruthi-1 board calibration instructions

Hi all,
Is there anywhere I can find the calibration info for the ir3109 filter board?


I don’t have the instructions but I can guess about half of he calibration procedure based on the other filter boards:

  1. Put the filter into self oscillation with max resonance and oscillators off
  2. Play notes and adjust the v/oct trimmer to get a proper octave interval
  3. Play notes and adjust range trimmer to adjust the pitch offset to get proper notes (with filter cutoff set to ???)


Thanks Bjarne but I’d still like some documentation since this particular filterboard has 4 trimmers to adjust, Gate, Reso, V/oct, Range.
I guess Reso needs to be set first in order to set the point of resonance where the self oscillation happens(?) and then set the V/oct in conjuction with Range to get an accurate scaling of filter tracking across as many octaves as possible. Clueless about the Gate trimmer.
I understand about the vintage board files to be removed from the repositories but what about some documentation to support the already existing ones? A quick search did not fetch anything…

If I remember well, reso sets the point at which the filter self-oscillates. You should adjust it so that the filter self-oscillates frankly with a resonance above 60.

Gate is an offset to prevent bleed in the VCA. Set the filter to self oscillate, wait for the envelope to finish its release stage, and adjust gate to the point at which the self-oscillation tone becomes impossible to hear. Higher, you’ll get bleed; lower, the envelope will be truncated.

Τhanks for the quick reply!I’ll try it later and post if I encounter any problems.One question though…where should the cutoff be in order to set the resonance? Is around 80 okay or should it be lower?

I doubt the resonance amplitude is very heavily influenced by the cutoff frequency! You can set cutoff at 63, and play a middle C…

Sorry but I can’t understand the whole gate thing, since the filter is in self-oscillation it will never stop being audible regardless if the VCA is triggered or not…The gate trimmer does not seem to be doing anything.

The VCA is after the VCF.

The “Gate” trimmer does nothing to the filter, it mitigates bleed in the VCA.

Ahh I got it now.I had to carefully listen and get the feel of both sustain and release times of the vcf envelope to hear the vca bleed after the release. It wasn’t much to begin with so I had to crank the speakers up and make it more noticeable first and then back it off until it vanishes…thanks again Emilie.