4x4Pole: Controller decisions

April 6, 2013

The build is proceeding nicely…

Firstly, the boards have been populated with resistors and most capacitors. The digital control boards are complete save for the OLEDs, buttons and pots, which will be panel-mounted. Tragically, and despite my heroic efforts at military planning/sourcing, I didn’t order enough 100n capacitors for the filter boards. I now diligently plan my next components order.

Quite some time has already been spent working on the case design and front panel. Using Inkscape, I’ve already ordered and received some test cuttings in 3mm acrylic glass. I’ve firmed-up on some nice ideas that I will expand upon in another post. Still deciding whether to invest in wooden cheeks, but then again, they can come later.

I’ve flip-flopped daily over whether to implement the Shruthi XT programmer, or stick with generic midi control. I’ve now firmly decided to not use the Programmer this time – though I did grab 2 PCBs in the latest bulk order, and I’ve already gathered the parts. The reasons are:

  • Using the programmer would mean direct control over only one Shruthi, which would be fine in Poly mode, but not ideal for other configurations (e.g. 4 independently-controllable monosynths).
  • By using the programmer I would lose CV control, and thus the ability to indulge my current joystick fetish.
  • I’ve got other cool ideas for the programmer. Foremost of which will be a keyboard version of the new Ladder filter. 😎

So, MIDI it is, and by chance I have an old beat-up Evolution UC-16 which I will be cannibalizing.


Quite easy to take apart….


I thought there might be an extra MIDI port hiding in there, but alas…


Now, these pots are a bit worn so they need replacing. I suspected they were 10k linear pots. A quick test confirmed this. Problem is that these pots are so welded to the PCB that the cleanest route is to just cut them off…


So now I can add my own pots and arrange then as I wish on the front panel. By also adding the keypad I will have access to 25 banks of 16 MIDI CCs, each knob being freely assignable to any CC on any channel. That’s a lot of control!


Further, this can take MIDI input directly over USB, so I can sequence the whole caboodle from a DAW if I wish. But where’s the fun in that?

And why stop there? I’m also integrating my as-yet unbuilt MIDIpal to make this a super-charged master keyboard. Better than the plastic shit available these days, and fully customised. Cheaper too.

MIDIpal has 8 CV inputs = Joystick pron! hehe

The bonus is that, with 4 Shruthis I will also have a routable 4-in 4-out MIDI interface.


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