Help with synth keyboard

Discussion in 'The Projects Forum' started by djex, Feb 28, 2011.

  1. djex

    Thread Starter New Member

    Feb 26, 2011
    15
    0
    I have been playing around with various oscillator circuits lately and soon will be trying to put them together into a small synth.

    Now I want to be able to play notes with the oscillator. At the moment I have two 555 timer square wave oscillators that are adjusted by a pot for the pitch. Now I know 555 timer oscillator circuits arn't proper synth material but I'm new to all this and it's a great learning project for myself.

    Id love to be able to have a series of buttons that I could implement into a 2 octave keyboard and with each button is a different note in the octave. I read about adding resistors between each button in series to produce a different note but I read on a few sites that this would not be 100% accurate.

    So my question is what can someone recommend in order to get accurate notes from each key press. Now you may say why does it matter if its just a learning project, well for one I like to do stuff right the first time and secondly I'm an artist my self and improper notes would drive me insane :p

    I read about keyboard matrices but can't seem to grasp the concept of how they work. Would this be what I need?

    I plan in the near future implementing a few types of wave forms into my synth with a few op amps I manged to scavenge off some old electronics. Would changing the pitch of a op amp oscillator circuit be similar to a 555 timer by changing the resistance? Sorry if these are simple questions.

    Hope someone can help. :)
     
  2. bribri

    Member

    Feb 20, 2011
    133
    5
    a keyboard matrix can get pretty involved, especially if you want polyphony.

    for a mono-synth, a string of resistors is probably just the thing. just using 1% tolerance resistor values would be pretty accurate i think.
    if you started with 5% resistors to get it all working, you could swap each value out with a pot, tune to your liking, and then just pop in the closest value E96 resistor. it's also possible to cheat by trial and error combinations of 5% resistors to get to your ideal value.
     
  3. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,771
    930
  4. djex

    Thread Starter New Member

    Feb 26, 2011
    15
    0
    Thanks for the replies. I'm going to play around with the resister idea you suggested bribri.

    Thanks for the link kermit2, should be helpful for the other components I plan to make for the synth.

    Just out of curiosity, how would one go about making a polysynth? I'm assuming then you would need a keyboard matrix to be able to play multiple notes at once? Also you would need a way to vary the pitch other then using resistance? For now I'm sticking with a monosynth but it would be good to know for the future if I decide to expand on my project. :p
     
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