This one? EricaSynths - EDU DIY VCF If so and if you ping @moritzklein they might be able to help.
Not sure what you mean by “cutting and opening very quickly” — these things are all normally designed for 1 V/oct response to the CV. Or did you mean the slope of the frequency response? If I’m reading correctly it’s a 3 stage filter so presumably rolls off at 18 dB/oct. A 2 stage filter would roll off slower (12 dB/oct) but I guess a diode filter can’t have an even number of stages.
Hi, yes thats the one.
I mean that in a few volts , not sure how many, the filter was either close or fully open. The version (erica synth mk) was still better for me that the first one though.
But i had to attenuate the EG quite a bit to get it to sounds nicely otherwise it would always open the filter fully. On the schematic you can see that the voltages for fhe cut off are attenuated quite a lot. I tried different values for the resistor on the main cut off point (27k here) but the change was not really significant.
Keep also in mind that it had a different resonant circuit so maybe that was not helping.
But again, it might be just a matter of taste.
That’s a combination of the 1 V/oct frequency response — which is increased (more V per octave, or fewer octaves per V) when you attenuate the CV — and the rolloff: with a steeper rolloff you need less change in the cutoff frequency to go from near zero attenuation to near zero output (and that does not change when you attenuate the CV). It’s also dependent on the signal waveform. One with mostly only low harmonics will go from full amplitude to nothing faster than one with a lot of high harmonics.
I guess my point is there are several things that can affect the thing your ears are perceiving and which you sort of need to disentangle if you want to improve it. If the CV response really is 1 V/oct that’s pretty standard — it means you can get similar amounts of filtering for high and low notes if you send the pitch CV to the VCF too, and it means you might be able to use the VCF as a sine VCO if it goes into clean self resonance — and you might pause to reflect before changing it (and just attenuating the CV will change it). You can try different signal waveforms to see if they all attenuate too fast for you, and you can look into a 2- or even 1-stage VCF for a gentler frequency response.
“a few volts”, by the way, corresponds to a change in the cutoff frequency of a few octaves — not really such a small amount.
So, you all made feel bad about the diode VCF so i went back to it and I got it working for my taste.
I got the following circuit
And I made a module of it. I named it Kresselle as it can sound quite like a crispy bird sometimes.
And I recorded a quick video so you can have an idea of what it sounds like.
I am really happy (and a bit proud as well) of it.
That sounds really nice!
