Virtual Knobs

I have done another round of simplifications for the design of the ISHIZENO ONE. This time around, I have worked on the knobs, and decided to go for an all-digital solution. My philosophy is that audio signal should be analog, but everything else should be digital, so that it can be recorded and replayed. This includes patching, thanks to our analog crosspoint switches, but it should also include knobs, which should be connected to rotary encoders driving digital potentiometers.

With this new design, 8 physical knobs are logically associated to the 8 polyphonic channels. These knobs use rotary encoders with 24 detents and 24 PPR resolution. They also provide SPST momentary switching and RGB led illumination. Pushing a knob selects the corresponding polyphonic channel, making all 8 physical knobs available as virtual knobs for the channel’s configuration.

Knob settings are passed to a channel through its I²C bus. Settings can be used from a channel’s shield using a digital potentiometer like the AD5254. Alternatively, all 64 virtual knob settings are converted into analog voltage levels through 16 built-in AD5254 quad digital potentiometers (2 per channel). From there, the voltage level of a channel’s virtual knob can be patched to any analog port of the channel, or any of the 16 or 32 analog endpoints available.

Here is what the new faceplate now looks like:



7 thoughts on “Virtual Knobs

    • I’m really glad that you like it. We’re still very early in the process, but I am quite encouraged by our progress so far. I will take you up on your offer to help with testing. We’ll focus on the hardware first, then build the iOS application. We will also need help for building some submodules as Arduino Shields. This is something that could be done right away. Thanks a lot for your help!


  1. Thank you for the fast reply! I look forward to having one in my hands! And I also build instruments and have some experience with Arduino (mengqimusic.com). I would love to design submodules for this beast! 😀


      • I didn’t meant to change anything now. But I do think it would be viable to have the controls on the bottom side and the jacks on top, instead of the current jacks around controls, which would make it easier to play.


      • I have been thinking about that, but I’m not sure there is a better solution, because if your other modules are on a lower row in your rack, you would want the controls on top. Also, having the 8 knobs around the screen make them behave like soft knob, which is what we want now that we use them as virtual knobs. Putting them at the bottom would reduce the visual link between the knobs and the graphical user interface.


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