My first kit, I bought the PCB from synthcube (they serve the orders from the MFOS shop as well).
It is a fairly simple affair and there is a stripboard layout posted on electro-music.com, but I would not
recommend that for beginners as you would need some troubeshooting skills.
Box from thrift store painted with Hammerite green paint and white posca marker. Sprayed on matte clear coat
The PCB has room for adding an external audio input to the filter and a external CV source for the VCO. These
mods are documented on the MFOS site and in the book Make: Analog synthesizers. It's really just a matter of adding
another mixing resistor (plus a capacitor for the filter) on the inverting inputs of U1-C and U2-A.
I also wanted to use external gate signals. My solution is crude and not so good (might make a better one later).
I simply added a jack which I connected with a 1 Kohm resistor to the center pin of switch S8. The ground pin on
jack is connected to BN, not the virtual ground. My Keystep seems OK with this but it's on your own risk.
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