MATRIXSYNTH: LMNC : Building the Kosmo 1222 Performance VCO

Wednesday, January 08, 2020

LMNC : Building the Kosmo 1222 Performance VCO


"The 1222 Performance VCO is my first Oscillator PCB Design.
Born from frustration of playing shows, or not having a tuner to hand and getting in tune enough to get going, instead of sitting around being out of tune. I tested it on my November tour, and did some fine tweaks to it afterwards.

Its also got an octave knob. a fine tune knob that is exactly an octave with a centre point of C making it easy to find the note you need. it is a rather standard oscillator apart from that, and in my opinion thats what you need.

Big simple controls, pulse width, PWM, fine tune, Extra CV, Sync, FM, Square, Ramp and Triangle outputs.

It also has a rear connection called LINK, which will be for future use, as i will be making an oscillator drive a nice means of driving lots of oscillators at once, as well as a mixer module so no need to patch all of the oscillators together they will be connected from the back. A final design is like a cross mod module that will turn em into a sort of fart box thing. This is all future ideas, but if you cant wait check the schematic it will make sense!

The build is reasonably simple it is explained in videos below. you will need to be able to connect an arduino nano to a computer, the code is available below.

Temperature drift. unknowingly i took these on tour to the extremes of temperatures. they spent most of their time in a 0 degrees celsius van, giving it plenty of time to cool the whole case through. then they were carried into room temperature rooms and immediately sound-checked. Then they slowly heat up throughout the night, and as more people enter the room the hotter the room gets and the hotter the case and oscillators get. the change in tune wasnt massive, only a few cents but i was very thankful for the tuners.. I noticed this effect more at smaller gigs than larger gig. i guess smaller rooms heat up more like a big old oven.

Anyway below is everything you need. any questions fire over, at the bottom is an FAQ with past problems/questions.

The Bill of materials links are the first i got to, if you look around you may find cheaper, these are UK also. if anyone in the US makes a mouser cart, please send my way it would be useful! i will try to make one, however there is no telling when that will happen.

below is the first video on this module, this was before tour, these prototypes i took on tour and they are largely the same as the finished things. The tuner code is a tad more finessed, plus i didn’t spend ages calibrating these!."

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