…now if I with these settings diual the actual cutoff to “0”, and then use my mod wheel it barely opens up the cutoff id say it only gets to circa 40% open. I’m at a loss.
I tried this on mine and it does the same thing. Even with the mod buss amount and the amount to filter all the way open the best I got was 50%
If I’m not mistaken, “On” is just a voltage. I don’t know what the value of that voltage is, but it might not be enough to move anything beyond the 40% you are getting.
Try pot mapping.
If I remember it right, the ON modulation source is about 5 V. So this would open up the filter by about 5 octaves. So when the filter is really down at. let’s say, 40 Hz (zero on the filter is way below this!), 5 octaves will open it up to 1280 Hz. The usable span of a filter is just way to high for ull range sweeps by a single control voltage.
Even on my modular synth here, it is not possible for most CVs to sweep the filter all the way.
So this is not something I would consider are weak point or a design error. Better use the touch surface for wide filter sweeps. This is working bipolar, so the left hand will give you lower then set cutoff, and the right hand higher frequencies. That way you get about the double of weep range. There is a reason for this touch surface.