CEM3391 and what to do with it?

Rolbista · Joined: Nov 17, 2012 Posts: 23 Location: Poland

Hey all, recently I scored an old Hohner PK-250 MIDI for cheap. I hoped to mod it like shown on this site: http://legoluft.dyndns.org/tech/repairs/e-pk-250.html but the the sound pretty much sucks and the keyboard lags a little, so I decided to pull two CEM3391 chips from it and use them for a project. Here's the deal: I'm just a poor boy, from a poor family who wants some fat and dirty keyboard sounds, but can't really afford a real synth that would fit my sound requirements, and doesn't want to go the "MIDI controller+PC plug-in" route. I WANT KNOBS! Ok, right now, I'm using an old Casio SA-65 with an added line level output that is fed though a fuzz pedal to achieve some "synth" textures, but I thought that since I have a chip that contains ADSR, VCA and a VCF, with addition of two 4069 LFOs, I could have all the synth effects and features excepts for VCOs. So I have a few questions:
- what i intend to build, is kind of a "keyboard pedalboard" with a signal chain going like this: Casio->fuzz->CEM3391 with LFOs for filter wobbles and tremolos.
- is the circuit shown in datasheets enough to make it work?
- datasheet says it needs +12V and -5V, can I power it with a converted ATX power supply, I wanted to use it as a PSU for kind of a "rack-esque" construction
- do I understand correctly, that I should lead control voltages regulated by potentiometers to corresponding pins in the chip, with switching jack sockets for external CV input from an LFO? Can I use the +5V supply line from the ATX as a source? what about Gate? What does it do?
- The Internet mentions, that this chip is "microprocessor controllable". Is this of any consequence to me?
- Chip seems to be able to control the filter with envelope. How do I go about it, do I feed the "enveloped" signal to the CV input of the filter?

Ok, enough for now, I hope I didn't exceed the question limit for a single thread, Cheers.

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