keyboard for 555 synth

[dprommasit]

has anyone seen this done? i (like many i'm sure) dream of making their own 8-bit "nintento" synth/keyboard

i was thinking of using the the simplest 555 circuit to make a square wave, and having a series of pushbutton switches with trim pots to control the pitch of each button/"key"

i did this once with a speak and spell that i used as an oscillator (had some cool sounding waveforms!), but my problem was that i was only modifying a constant tone....then i thought...what if there existed mini dpst momentary pushbuttons? i could then trigger the sounds and modify the pitch simultaneously!

the other option i worked out is getting a bunch of 556s and rigging an osc to EACH KEY which i believe would equal full polyphony? but this seems ridiculously inefficient.

i'd also probably make a blinky circuit for a vactrol to get some vibrato!

any suggestions of a good way to approach this? i couldnt find many people that have tried to do this and have documented it very well...

just a pipe dream i've had since before i even was enlightened about the existence of diy synth/circuitbending stuff!  

[marmora]

Maybe there's some useful info in this thread:
http://www.circuitbenders.co.uk/forum/index.php/topic,1542.0.html

I think it would be a ton of fun if you follow through!  Do keep us updated.

[hackertronix]

i've been wondering the same thing myself. here is what i am going to try:

you know where you normally place the potentiometer for pitch? instead, try a parallel circuit of trimmers (500k for wide pitch range for tuning the notes) and normally open push button switches (for the keys).

you can carefully plot out where the keys will be on the box. i think what i will do is line them up, and place the "black key" buttons slightly above the others, so they will resemble sharps and flats.

you will need around 12 switches for one octave of notes. (the octave is the 8th interval in the musical scale, but with the sharps and flats, you need 4 more for a whole chromatic scale). i think i will go with 14 switches, since i would like a first inversion note (a note below the "1") and a 9th note.

[BrassTeacher]

Actually, you need 13 keys for a complete octave. An octave is 12 half-steps yes, but musical things never start counting at zero. So, for a keyboard that completely covers from C-to-C, if that's all you want, you need 13 switches. If you want to go from B-to-D, you will need 16, unless you want to leave out the upper C#.

[ultraclean]

i had some success using a resistor network in a "ladder" style with some momentary push buttons triggering a 555 osc. the biggest issue was finding the right resistance between each step to get it to as close as possible to true semitones. came out pretty well though :]

-ajax

[AttDestroyers]

This guy did a good job with it. Same concept... kinda. He used all CMOS 4000 logic chips instead of the 555.

http://www.jacobwatters.com/c-monster.php

I've started work on a similar project. It'll probably be a while before it gets done though. I'll try to post results when I'm finished. I want it to be polyphonic, so I'm looking at building an osc. for each key using the 40106 IC (6 osc. per chip). Probably 36 keys.