CMOS keyboard

jcintheus · Joined: Oct 16, 2011 Posts: 59 Location: Colorado

Wanted some "regular notes" so, I built a top octave generator from 2 40106's, 12 caps and 12 multi-turn trim-pots.
I divided that with 6 4520's for 4 octaves.
Using an old 44-note organ manual and 11 4081's to "gate" the dividers I ended up with 44-note polyphony!
It's not without its problems, the output is too weak to drive other
CMOS circuitry, which was kind of the point.
Here's a sound sample, using the keyboard, some shiftreg's, and other tuned osc's.
It's in the key of D.
http://soundcloud.com/bill-chavez/passant-regardant

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textual · Posted: Sun Jun 24, 2012 2:07 pm Post subject:

who thats super cool! i assume this provides a CV of sorts to drive say an oscillator? polyphony? schematic? sound sample sounds great! why not then use an op-amp or a CMOS booster circuit with 4049 to get the level back up?

Cynosure · Posted: Sun Jun 24, 2012 3:47 pm Post subject:

Very cool. I did something similar a while ago but added the option to play dual top octave sets with one an octave higher. then i added a bunch of other cmos stuff all within the same housing (schmidt trigger, dividers, sequencer, Wasp filters) and have both an input and output for the sequencer clock. More info on the site in my signature.

I am intetested in seeing a schematic of yours if you have one.

attdestroyers · Joined: Mar 29, 2012 Posts: 47 Location: Malvern, Ohio

This is awesome. I've been researching this a bit because this is definitely the next step for me and my lunetta. I'd love to see any schematics or additional info you have.

Cynosure - Your C-monster is awesome.

jcintheus · Joined: Oct 16, 2011 Posts: 59 Location: Colorado

Ok, so here is a partial schematic. There are 2 40106's to provide 12 oscillators.
One for each note. 6 4520 dual binary counters divide those 12 notes 4 octaves each.
44 of those notes are gated by +V via 44 AND gates.
This show the scheme for one note through 4 octaves.
The outputs (all 44) are summed with resistors.
Also, there are pull down resistors on the gate inputs. (not shown)

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richardc64 · Posted: Mon Jun 25, 2012 8:06 am Post subject:

jcintheus · Joined: Oct 16, 2011 Posts: 59 Location: Colorado

Cynosure · Posted: Mon Jun 25, 2012 8:43 am Post subject:

What i did with mine was I actively mixed them with an opamp. I used a pot for the feedback resistor on the opamp. When I want a nice polyphonic mix for sound then i turn the pot down so there is no distortion. When I want to use the sound to drive other CMOS chips then I turn up the pot, which increases the amplification on the output.

jcintheus · Joined: Oct 16, 2011 Posts: 59 Location: Colorado

Cynosure · Posted: Mon Jun 25, 2012 9:32 am Post subject:

There isn't a schematic on my site. I worked from bits and pieces of various schematics and some stripboard layouts.

I basically did this without the pots on each input:

http://sound.westhost.com/articles/audmix-f4.gif

Also, I think i used 100k resistors on the inputs, and R4 was a pot (I think either 100k or 500k).

richardc64 · Posted: Mon Jun 25, 2012 10:50 am Post subject:

JL · Joined: Jun 25, 2012 Posts: 20 Location: New England

This is really cool! I've been wanting to do something like this for some time, but finding a proper keyboard has been difficult. Where did yours come from?

Your design is very similar to combo organs of the 60's. The difference is instead of gating the oscillators with the key, the key would send the oscillator to a common buss (usually one per octave), which would then be filtered and mixed with the subsequent octave busses. The downside to this was that you needed a key switch for every footage and a buss for every octave of every footage so for a nice full sound with, say, five footages, you needed five switches for each key, making the whole key assembly rather bulky.

Well done! At the very least you have a polyphonic square wave synth, which is totally rad.

Cynosure · Posted: Mon Jun 25, 2012 11:50 am Post subject:

For mine I just used a regular scanning type keyboard. I attached the outputs from the dividers the appropriate keys at the solder point where the diode is connected, on the side of the diode closest to the switch. The pcb for the keyboard mixes all the key outputs into a few buses, which I soldered together with a strip of bare wire and then I took my output from there. the mixing resistors were at the divider outputs (although I was later told that it is best to have them close to the opamp if possible).

And this top octave method is extensive no matter how you go about it (even with a MK50240).

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

richardc64 · Posted: Mon Jun 25, 2012 12:36 pm Post subject:

jcintheus · Joined: Oct 16, 2011 Posts: 59 Location: Colorado

jcintheus · Joined: Oct 16, 2011 Posts: 59 Location: Colorado

attdestroyers · Joined: Mar 29, 2012 Posts: 47 Location: Malvern, Ohio

Awesome recording! sounds so good! This is starting to get pretty complex with all the divide then multiply stuff though. I think I'll try to figure out a simpler solution when i do mine. probably not possible, but ya never know.

JingleJoe · Posted: Tue Jun 26, 2012 11:45 pm Post subject:

The part around 1 minute sounds awesome Shocked

maybe I'll make something like this, how did you acheive the sound in that section, jcintheus?

jcintheus · Joined: Oct 16, 2011 Posts: 59 Location: Colorado

JingleJoe · Posted: Wed Jun 27, 2012 6:20 am Post subject:

jcintheus · Joined: Oct 16, 2011 Posts: 59 Location: Colorado

JingleJoe · Posted: Wed Jun 27, 2012 8:58 am Post subject:

I'm aware of thier relationship Smile

I recently did some work into calculating the frequencies of notes in a scale. For a better sound it is better to go with just intonation. I think, if I remember correctly, just fourths and thirds are very close to thier equal tempered counterparts too.

jcintheus · Joined: Oct 16, 2011 Posts: 59 Location: Colorado

JingleJoe · Posted: Wed Jun 27, 2012 11:01 am Post subject:

aye thats a very useful feature Smile

I plan to impliment the same tuning method if I make a cmos synth this way.

jcintheus · Joined: Oct 16, 2011 Posts: 59 Location: Colorado

So, here's another CMOS keyboard track.
http://soundcloud.com/bill-chavez/the-money-programme

This time I sent the summed output to a mixer then used an lm386 to boost the analog signal back into CMOS range.
Then I divided by 2(4027) and multiplied by 3(4046 and 4027) for a nice full tone.
The 4046 used in the multiplier circuit is responsible for the 'falling" tones between key presses. (The Drall laser effect)

Just a bunch of cheesy midi instruments and the CMOS "Synth"