video synth ideas

edited May 2010 in Everything Else
Hey... So here's something interesting I just found that might be of use to anyone interested in messing with video synthesis:

The DoubleDeka VCO -- Ian Fritz is claiming that the core is capable of oscillating up to 200kHz; tracking seems very good (I don't think this is super important but might be useful if one was interested in synthesizing video & audio signals at the same time...) From what I gather the oscillator core outputs just a pulse signal, which is divided for each signal and steps through the sliders to generate the analog voltage at each moment.

It's also capable of syncing (resetting the oscillator waveform) to H or V sync pulse.

Currently available at as a module, kit, front panel, or PCBs...
I'm going to put one of these together soon...


  • The LM331 is a great IC. I'd be more curious about that circuit if he'd post a schematic. It sounds like a fast oscillator with a divide by ten counter and some analog gates.
    Still, syncing is a good idea as is having oscillators track.
    Thanks for the link!
  • Critter and Guitari had another batch of the videosciloscope posted. Have one on the way, it outpouts to the yellow coaxial so I should be able to sue it with a projector off a board send. Disappearing off board for a few weeks , work trips, Todd if Mark II drops soon save one for me!!
  • Godspeed, and I'll check out that scope!
  • re: the 311, it's all in here Todd:

    You could try asking Ian directly about his implementation; might not give the whole thing but maybe a lead or two.

    frijitz [.[at]'] yahoo [--[dot],,,] com

    (Haven't been round here much lately, but school's finally out...!)
  • Hey! Yeah, I've cuddled up to that app note. After some less-than-ideal performance from a 4046 based VCO for WTPA2 that I breadboarded, I changed the design to be based on the 331. Both that app note and the datasheet are a little light on the equations I want so there will be some tweakery yet.
  • Welcome sir!

    For reference, same idea (current versus voltage control) was used with a 4046 here: (take a gander at the schematic).

    Good luck!
  • Riiight --
    Thanks for the link! You know I didn't bother to try using a current sink, which would have been a good idea. 400:1 tuning is a little short, but I could live with 500:1.
    Perhaps it's worth getting the breadboard back out.
  • There's also this article in an old EDN book which does a good job of describing this topology:

  • Hey! Tim Stinchcombe just wrote to me -- nice guy -- and pointed out that the 400:1 range he's talking about in his circuit is the ratio of clock frequency to filter cut-off and not the actual range of the VCO, which is actually greater. So my bad. Breadboard ahoy.
  • edited July 2010
    Lovely little kidney shaped jackson pollack painted clear panel with a ghostly white pcb w/2 pots attached showed up from critter. I am mucking with feeding it a send off the mixer while I go. Lots of fun. Its heading in the right direction but I'd like even more chaos!
  • Huh! Send me a link. I'd love to see what they're putting out. As you all know I really like that guy's circuits.
  • Whoa. Yep, they've been busy:

    Their circuits look nice and simple too. I'd love to see schematics. Looks from what I can see like they're still rocking the RC phase shift stylez.
    It's fun to have competition and be like: betcha I can get some waveforms they can't :-) Maybe that's a jocky way to think, but hey, it's fun.
  • I like the "enclosure" for the first thing linked there. Cool idea.
  • it's a pity that they dont make video critter boards anymore tho

    that would have been a cool project to mess with
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