[sdiy] Minimoog Keyboard Interface

[Dave Leith]

great project and documentation. It will be super when all finished!

Dave

On 5/23/10, Joe Rounceville <jrounceville at hotmail.com> wrote:
>
>  Hello everyone,
>
>  I've been monitoring the SDIY list for a long while, but couldn't figure out why I was unable to post to the list.  Rick helped me figure out I was sending HTML emails instead of plain text... duh.  Stupid "smart phones"...
>
>  So I'm in the process of building a Minimoog Model D clone from the service schematics (and I'm a bit of a newbie to EE... well, maybe not a pure newbie anymore)... at least that's what I'm starting out doing... I anticipating using it more as a starting platform to build lots of other stuff.  For example, I want to design an auto-tune circuit at some future date, and a MIDI interface (maybe using the midibox designs, although they seem a bit like overkill).  So I'm going to end up with an analog synth with some helper digital stuff to make it more usable.  I'd really love to figure out how to build in some form of patch memory, but that's a tough nut to crack on the original Mini.  Who knows, if I get it all working nicely, I may even consider figuring out how to turn it into a poly.  I wanted to start with a very solid base project, and I couldn't think of anything more solid for a core than the venerable Mini.
>
>  My project blog is at http://sites.google.com/site/minimoogwiki
>
>  It probably borders on hopeless to try to find a real Pratt-Read keybed (at least at a reasonable price), and that's about where I'm at.  I've got just a few more circuits to build (contour generators) before I'm going to be stuck on "the keybed problem".  So I was hoping somebody could give me a bit of a hint on how to take a modern poly keybed and build a conversion circuit so it could be hooked up to the keyboard interface circuit of the mini.
>
>  The keyboard interface circuit has six leads, but I honestly don't know how the mini keybed works.  It looks like one line is +10v in, another is ground, another is "pitch", which is probably a voltage value that varies based on which key you're depressing.  Another line is labelled "trigger" and another is labelled "keyboard trigger in".  Finally, there's one more labeled "8.48ma", which seems rather strange, but I'm guessing that means "8 milli-amps at some unknown (perhaps varying) voltage are continuously supplied here by _something_".
>
>  So, to convert a poly keyboard I need to know enough about this keyboard interface circuit and the original Pratt-Read keyboard to get enough context to start to build some kind of DAC based circuit (maybe with a PIC or something I suppose).
>
>  If someone with familiarity with the keyboard interface circuit on the mini can help me get my bearings, I'd really appreciate it.
>
>  Thanks,
>
>  Joe R.
>
>
>  P.S.  I hooked up my VCF to the reference oscillator after I got it done.... wow, that old filter design sounds great even on something as boring as a 440hz sine wave!  I can't wait to get it all up and running!  My band mates will probably flip out.
>
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