CMOS Melody Generator w/ Oscillators

[SonusFluxa]

Tabby's idea of a relatively simple DIY modular synth using vero has had me on a hunt for schematics that look interesting, and that I would have the ability to lay out. I found this on the electro-music forums a while back, but this schematic from hackaday finally clicked with my brain. Just finished this little goon a few hours ago. My understanding is that the three inputs on the 4051 are fed LFOs, which then alter the melody that is generated using the oscillator fed into the 4017. I've also included the simple 40106 oscillators that I used to drive this. I'm going to go back and change the fixed resistors to pots on the LFOs, to add a bit more movement and playability.

[notnews]

Sonus, you are always up to the coolest things! Thanks for sharing this.. it gives me a few ideas of my own.

If you've build this up I would love to hear what it sounds like! awesome work.

[tabbycat]

hey sonus, that looks very curious. would be interested to hear anything you get out of it.

is it some kind of randomised sequencer? i recognise the 4017 from a few baby 8 sequencer layouts.
i don't know much about the 4051 but have seem that freppo (agent cmos!) has made good use of them in randomising roles: https://www.youtube.com/watch?v=eTS0hV_PigA
http://www.diystompboxes.com/smfforum/index.php?topic=109237.20

thing on 4051 https://www.youtube.com/watch?v=YHOmru_t_-k

i have decied to start my vero modular synth project with a 15v (standard synth) korg ms-20 filter (with high and low pass options, if i can work out how to implememt the switching) in a stompbox. that way i can use it as a stand alone filter until i get the rest of the modules built up and it can go into a rack.
here's the one i'm trying http://electro-music.com/forum/phpbb-files/ms20_filter_358.png

the 358 will take 15v without issues (fine up tp 32v), i may use the voltage doubler from 9-18v or just go stright in with 18v. straight in i think, as it is just less fuss and junk to potentially blow up.
thread here at electromusic (which i joined a couple of weeks ago) http://electro-music.com/forum/topic-43085.html
there's another layout there but it's pretty massive and wouldn't fit in a 1590b without tiddling around so i went with gila's.

as for a nice vco with nice options for all the major waveforms (a good true triangle seems to be the trick, some have fake triangle type waves), am looking at finding a vero or cheap pcb something along the lines of this:
https://www.muffwiggler.com/forum/viewtopic.php?t=119355&postdays=0&postorder=asc&start=50
the reviews for this one are very positive and the pre smd soldered board seem a good deal. some of the fundamental core synth stuff gets to the point of too big to do on vero easily, while filters and lfo etc are far more vero friendly.
if i only treat myself to one pcb then it will be a good vco, as that is the foundation for everything that follows. if your original wave is shitty then all the nice filters and modulation in the world can't compensate for that. although shitty is nice sometimes.

for lfo i may try to adapt the tremulus lune to a modular set-up. for modulation and delay, lots of vero stomps here to choose from that can adapt to module format, preferably something that can take 15v for better headroom and to keep everything on the standard 15v format.
baby 8 (if i ever get mine working) for basic sequencing. that's a real pita build. offboard wiring hell. am sick of looking at mine so will leave that until last.

have got some little square aluminium panels eurorack height so i can start thinking about a rack format. a couple of £ each from fleabay for the pro touch.

anyway, that's my basic plan as far as i have one .

re your stand alone oscillator build, the 40106 (fairchild) are max 15v but i will have a look around to see if there is something else drop-in-able that will take 15v more comfortably. i wonder how long the 40106 would last being run at 15v?

[SonusFluxa]

Here's a demo of the melody generator in action.

I recorded a demo of the melody generator and the oscillator layout that I posted, but the few times that I tried, soundcloud wasn't cooperating. This demo, however, works fine.

This is the generator, but instead of being fed a single oscillator and three fixed LFOs, it's being driven by this:



The schematic for this layout can be found here, from the same hackaday article that featured the melody generator schematic.

Driving it with this gives a few advantages. You have the same control over the general pitch of the looped melody, as well as added control over the total speed (both of which you can hear me messing with toward the beginning of the demo). What I find really interesting is the addition of two momentary switches that respectively feed it +v and ground signal, changing the pitches that are looped based on how long and when each is pressed (which is what is happening at the end of the demo).

TL;DR, yep, randomized looper.

Tabby, awesome to hear your synth plans more in depth! I'm currently going more the lunetta route (what up electro-music), but want to eventually box it all up in a wooden case, and plan on building patch cables and passing it off as a modular with front panels etc. Ordered blank metal cut to eurorack size from a distributor here in the states, which wasn't super expensive.

I'm definitely going to check out that filter layout, seems interesting and definitely a necessary addition to any modular. For an LFO, I'm thinking of using the Psycho that Alex laid out for us a while back, maybe modding for switchable random/constant.

As far as powering, during the testing and building I'm currently just using a 9v wall wart, but plan on using 12v if possible, as it's the eurorack standard, and would like to eventually build up a eurorack modular as well (you know, once I'm completely loaded), and maybe they could play nice together. I'm lucky to work within walking distance of a store that specializes in synth and specifically in eurorack, which I've been avoiding until now, for fear of emptying my bank account. However, the time has come to make a trip.

If you're using 15v, and building your own modules, couldn't you include a voltage regulator (the way that all of our pt2399 layouts include the L78L05) to make sure you don't blow out your chips?

Currently laying out an ADSR envelope generator, which I'm going to have to test and debug, but will post once it's complete. I'm also on the hunt for a decently DIYable VCO. Been looking at the MFOS, CGS, and Synthrotek models, all of which are probably too complex for vero of a reasonable size. I etch boards sometimes, but at that point I think it makes more sense to just buy a board from the manufacturer and support their future endeavors. If I find anything that would come out reasonably on vero, you can bet I'll  try my hand at a layout and post it here.

I'm also working on a 4069 kick drum oscillator (also from the hackaday column), but have to go back and check the layout to the schematic/do a bit of debugging before I feel comfortable posting that here.

[skeletonghost]

Here is a layout I've created from Sebastian Tomczak's fun with Sea Moss. Castle Rocktronics http://castlerocktronics.com/modular.html is also an amazing resource for Modular Lunetta perfboard layouts.

[SonusFluxa]

Thanks for posting the layout, skeletonghost! If I'm not mistaken, that's a component of the peyote space explorer.

Heads up for those interested, found a reasonably compact vco schematic with a decent amount of options, just finished the layout and will report back with results. Finished the ADSR layout, but waiting for chips to arrive.

[SonusFluxa]

Got the VCO working last night, here's my layout (diodes are unmarked on the schematic but I successfully used 1n4148):