Audible stair-stepping distortion of microfreak filter cutoff, driven with CC#23

Freak MicroFreak
#1

Hello. I have a microfreak with latest v5 firmware. I’m mostly playing it from various MIDI controllers via DIN MIDI.

My issue occurs when I use a hardware controller like a knob or modulation wheel to send MIDI CC#23 messages, to control the microfreak filter cutoff. In principle it works very well, but in certain parts of the cutoff frequency range (mostly in the lower range), and while I’m moving the controller at certain rates, I hear a quiet (but distinct) distortion. I’m pretty sure it’s related to the stair-stepping of values of the 7 bit CC range.

What’s interesting is that it is more audible with some oscillator models than others - it’s worse for the cleaner VA-types than most others - but I’m guessing that must be to do with harmonic content.

Also, the problem vanishes if I set up my cutoff control in a different way: sending channel pressure from my controller keyboard, and using the microfreak mod matrix to route pressure to filter cutoff. Then, even with a full strength modulation setting there’s no stair stepping or distortion - somehow the matrix is smoothing it. Despite channel pressure also being only 7 bit resolution. Problem is, pressure is unavailable to generate from a knob or wheel on many MIDI controllers.

I’m doing everything I can to make sure there isn’t some unseen complication here. Nothing else is simultaneously modulating cutoff (eg. assignments in mod matrix, envelopes or LFO). Also I’m using apps to check the data stream from the MIDI controllers, to make sure there aren’t any un-smooth jumps or value spikes.

So it looks like this is a by-product of the way the filter cutoff suddenly changes. Is there any way, maybe in a future firmware, the response could be smoothed or slewed?

As an aside - I also hear stair stepping for CC control of other parameters, like oscillator Wave, Timbre and Shape, but that’s easier to accept, especially for some of the digital oscillator types, where there probably are only so many discrete states/steps. But for the analogue filter - keeping my fingers crossed there might be a solution. Many thanks.

#2

Update: I spoke too soon about the channel pressure and mod matrix solution. A bit more testing reveals the stair-steps are there too. Blast!

(And for that matter, it’s even possible to produce the effect from the built-in keyboard. Init patch, filter cutoff to minimum, patch pressure to cutoff with amount 100, play top G on keyboard and quickly vary finger contact on the keyboard. For me that produces an obvious hollow-sounding distortion behind the note as the cutoff changes. If I remove the mod patch, and make the same min-max filter sweep from an envelope, it’s smooth, with no distortion.)

So my wish would in the end just be some kind of smoothing on the filter cutoff response, from any MIDI CC, pressure or even keyboard input. Could it be possible, Arturia gurus?