polyphonic synthesizer

Discussion in 'The Projects Forum' started by peltier_cooler, Jun 6, 2009.

  1. peltier_cooler

    Thread Starter New Member

    Jun 4, 2009
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    I am interested in making a polyphonic synthesizer (because I want to make a roll-up keyboard). I could gut an existing one and see how that's done, but I thought it would be fun to build one myself. I actually got as far as looking into analog synths (there is a lot of information out there) but realized nothing I was looking at was polyphonic...

    So I'm back looking for a digital polyphonic synth schematic. I have NO IDEA where to look for something like this, and my (extensive, three-night) Googling has yielded naught.

    Please help me. I'm not yet desperate, but my shaving razor looks at me seductively every morning. ;)

    Peltier Cooler
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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  3. John Luciani

    Active Member

    Apr 3, 2007
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    There is synth-diy group that may have some specific http://dropmix.xs4all.nl/mailman/listinfo/synth-diy

    Are you going to build the keyboard or just the electronics? You may
    be better off adapting an existing rollup keyboard and adding the electronics.

    I would suspect that most synthesizers use a uC to scan the keyboard for
    keypress events and then generate the signals using a DSP or custom
    chip.

    Some of the older analog gear used a top octave divider to generate
    the top 12 notes and the divide-by-2 circuits to generate the lower octaves.
    These chips are probably only available through salvage.

    I believe the Polymoog had one oscillator per key.

    (* jcl *)
     
  4. peltier_cooler

    Thread Starter New Member

    Jun 4, 2009
    3
    0
    Are you going to build the keyboard or just the electronics? You may
    be better off adapting an existing rollup keyboard and adding the electronics.

    That's the ticket. I'm pretty sure I'm going to try this.

    Don't know why I didn't think of it.
     
  5. Model-D

    New Member

    Jun 4, 2009
    1
    0
    The Polymoog Synthesizer was unusual among even the few polysynths of it's day and was arguably more akin to a highly sophisticated electric organ in it's operation. A double set of divide-down circuits gave two notes to each key which wer then available for the usual ADS (Moog's envelope generators had a common value for both the decay and the release stage) processing and modulation. Quite bizarrely, if understandably it had only one filter although there were triggereing options. The Polymoog Keyboard removed most of the user controls leaving operators with (I think) 14 presets.

    The most practical and cost effective way to build a polysynth today might be to utilise an off the shelf keyboard controller to generate a stream of midi data relating to note/s on and off, and velocity. More sophisticated controllers have aftertouch although this is usually not polyphonic - unless you want to spend big bucks. What you do with your raw midi data is where your creativity and ingenuity comes in ! You could build a set (upwards of five ?) of VCO's, filters and envelope generators and use a midi note number to control voltage converter chip or a pre built module from a company such as Kenton . Whichever way you do this - it's going to be expensive. Have a look at Oakley Sound Systems site for an idea of the cost involved.

    If you just want a usable polysynth, you could do worse than to buy an inexpensive controller keyboard, an old PC and run a VSTi such as one of the many minimoog emulations - one of which is bundled free with Pinnacle's Cubasis 5 ( around £10 - £20). Although the real minimoog is mono, the various VSTi versions are all poly and can sound quite stunning. There are also virtual Prophet 5's, CS-80's available and pf course, loads of free and shareware applications on the web - that's if it's just the sounds that you're after and not the thrill of building your own polyphonic monster.

    Whatever you decide - good luck !
     
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