Polyphonic Synthesiser - The digital keyboard assembly and debounce circuitry

polyphonic synthesiser elektor may 1982 - 5-17 polyphonie s"idi~e).%ise,ir GoÃàtz and R. Mester the digital keyboard assembly and debounce circuitry The general principles and basic theory behind the new Elektor polyphonic synthesiser were introduced in the March 1982 issue. However, this article is devoted to the practical side, namely the constructional details, thereby enabling readers to commence building. We start off with the debounce circuitry for the keyboard contacts and the input unit (together with its bus board) which acts as the keyboard interface for the main CPU card. The digital keyboard design caters for up to five octaves (61 keys). Although it is obviously possible to use fewer keys, the relatively small price difference be- tween three and five octave keyboards prompted the designers to go for the latter. This also means that the range of musical possibilities can be exploited to the full. The keyboard contact blocks, or switches, are mounted on eight individ...