ModBox 37 & Casio SK-1
This is a project I've called the ModBox37. It's an adaptable modular performance controller and breakout box with a 37 point patchbay and a few other goodies meant to expand the functionality of external devices, including a Highly Liquid UMR2 which adds MIDI I/O, an LTC1799 precision oscillator for replacing internal clocks and resonators, a simple square/triangle LFO, and a patchable control panel that gives access to touch contacts, photoresistors, momentary pushbuttons, toggle switches, pots at various resistance levels, and multis.
The first device I built out to take advantage of it fully is the pictured Casio SK-1. For as much as I've circuit bent over the years I never took a proper stab at that classic! It connects up to the patchbay via DB37 cable, and hooks into the MIDI I/O circuitry via HD15. It's also got a switch to bypass the SK-1s internal anti-aliasing/lowpass filter, a hard cut switch to the pitch circuit (for using the ltc1799 as a clock replacement), and a matching paint job.
10/1/2019 update: Another device, a circuit bent analog video signal converter, was built to take advantage of the MB37 as well and can be found here.
1/12/2021: The “currently unassigned” now control a basic little Atari Punk Console, with CV going to the “currently unassigned” patch points and audio coming out of DB37_34.
Progress photos
The physical base of the project is a BUD Industries PC-11495. The UMR2 board, which had been discontinued by Highly Liquid, was found by a seller on eBay by the name of fukakoryoku who is still selling them with pre-programmed CPUs at the time of this writing.
Patch & Control Layout
The “currently unassigned” bits were initially for a dedicated filter, but I’ve had issues adapting the filter I built to this ecosystem. I may revisit it/build a different one and implement it later, but I may also just build a 555 Atari Punk Console and use the available patch points and two knobs for controlling that & adding CV in to it.
SK-1 & Misc. Reference
This extremely basic schema just goes over what I broke out to the MB-37 from the SK-1 board, and the layout is explained above. If you’re looking to recreate something like this, be sure to look into Reed Ghazala’s original SK-1 Aleatron bending schematic, the Papernoise Concertodrone, and poke around online forums as well (esp for things like the anti-aliasing filter bypass which is SUPER important imho). There’s a wealth of info on this thing online and my documentation here is limited, and is also a sort of amalgamation of information gathered from others (with a little experimentation added on top). Some additional good SK-1 info here.
July, 2019
Note: It can be a lot of work documenting & making guides for builds like this, and credit it is always appreciated. More than anything, however, I’d love to see what you do with my info - if you do use the information on this page, please get in touch with me using the about/contact page; I’d love to see what you create!