Hi midiboxers,
let me explain this mysterious title.
Having recently found a disassembled yamaha pss-595 in a trash bin (!) I couldn’t decently leave to rats, I brought it back home to see what I could do with. Most of all I was interested by the idea of playing on a real keyboard, instead of the bunch of switches I’m using. (My computer keyboard does this too, though a bit non-intuitive). I first tried with the electronic board (with built-in midi ports), which was seemingly complete and in a rather good state, and I actually got midi note messages sent to the computer. Only, it behaves too strangely to be playable … sometimes it works, sometimes not, sending random notes, forgetting some note-offs, and it rapidely comes to crashdown until I switch it back on. Plus, I tried it as standalone, but integrating it in my midibox would involve the use of a merger, and I’d rather keep the building of a merger for more serious needs… So I studied the working scheme of the keyboard itself, to connect it directly on my DIN module. That’s where I need some ideas, because I miss so imagination here…
So this is a 49 keys keyboard, of course I could replace the circuitry with 49 contacts then connect it directly to the DIN, only this would involve ordering some more 165’s and I’m pretty sure there is a way to “cheat”. The keyboard output is a 15-pin port, and here’s the way it works :
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the first 9 pins each correspond to 6 contiguous keys (one semi-octave)
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the last 6 pins are for which key in a given semi-octave is pressed.
That means, when you hit the lowest key (C0) for instance, a connection occurs between pin 1 (lowest semi-octave) and pin 10 (first key of lower semi-octave). When you hit C#0, these are pins 1 and 11 that are connected ; when you hit F#0 (the sixth lowest key), these are pins 2 and 10 (first key of the second lowest semi-octave), and so on (please let me know if those explanations are not clear, I’ll try to make a drawing).
Not to simplify things, these are not simple connections : the impedance is infinite when the corresponding key is not pressed, but around 850 kohm when it’s pressed.
Is there any way to turn this working scheme into one interpretable by the DIN ? (I thought of using transistors … or replacing the contacts, which are made through a sort of conducting high-resistive foam). I only ask this question because I find this “matricial” aspect very interesting, it could spare me many DIN circuitry, that’s a matter of space (I would deal later with the programmation aspect, especially in the polyphony handling when playing chords). If nobody can show me the way, I surrender and go for new SR and a re-conception of my DIN module. I’m not looking for complete solution, just clues, ideas, or suggestions are welcomed…
Thanks by advance. Dubs
