Wednesday, 9 October 2013

Overcycler, the software

I worked on the software these last days, it's of course based on a good chunk of P600fw (envelopes, lfo, assigner, midi, storage, ...)

Besides a few PCB bugs I worked around in software, or using the soldering iron, the hardware works great :D

The microcontroller is really powerful, which allowed me to use very high sample rates (90Khz wih 2x oversampling, so effectively 45Khz), there is very little aliasing up to the highest MIDI notes.

Something I wasn't sure about was CV sample and hold performance (basically, it's a modern simplified version of the Prophet 600 design).
I was happy to see that it's very stable, and slew rate is great :)
 Here's a VCA envelope example:

 We can see that the fastest attack speed is below 100 microseconds (most analog synthesizers are 10 times slower !).

Noise was a problem at first, but  using various tweaks, it got much better (signal to noise ratio goes from 50db for oscillators to 100db for the master mixer now).

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Here's a little demo I made recently: http://sfx.gligli.free.fr/zik/overcycler/overcycler3.mp3
(Simple saw patches, I can't use the potentiometers to tweak the sound for now)

And an older one: http://sfx.gligli.free.fr/zik/overcycler/overcycler2.flac
(I had noise problems at that time, but it' a better raw sound demo)

I also set up a github repository for code and schematics: https://github.com/gligli/overcycler
(PCBs are still buggy tho)

PS: That's all for now, have a nice read :)

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