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etaoin
Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL
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Posted: Fri Nov 09, 2007 5:38 am Post subject:
VCO for Ken Stone's Wavetable |
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I'm looking for a VCO for my CGS Wavetable. So really the only requirement is that it tracks well in the higher octaves. It doesn't need to do anything else (no PW, FM, sync or whatever).
I've already seen the original Digisound design, but buying a CEM3340 just for this is a bit OTT. _________________ http://www.casia.org/modular/ |
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softfin
Joined: Oct 11, 2006 Posts: 271 Location: Far in the north
Audio files: 1
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Posted: Fri Nov 09, 2007 5:53 am Post subject:
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Would a stripped down CGS48 be sufficient? You can easily just leave out everything you don't need.
My CGS VCOs track fine about 7 octaves. In that regard they're actually the best ones I've got this far |
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etaoin
Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL
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Posted: Fri Nov 09, 2007 6:00 am Post subject:
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I actually have a CGS48 board lying around, with minimal components on it.
The number of octaves it tracks is not really important. It needs to track well way above the audible range. It actually doesn't need to track the audible range well at all (great if it does that as well, but not necessary).
Most VCO's I have tail off when getting into the higher frequencies. _________________ http://www.casia.org/modular/ |
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goldenechos
Joined: Jun 06, 2007 Posts: 201 Location: Marshall, NC
Audio files: 1
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Posted: Fri Nov 09, 2007 6:49 am Post subject:
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Take a look at the High Frequency VCO TH used in the SN-Voice to expo. control the tunable noise.
Another possibility would be the electronotes based oscillator that Ken Stone used in his Bi-N-Tic Filter design. This oscillator should track pretty well above 20k.
I think either of these could be made to work.
Tony |
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etaoin
Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL
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Posted: Fri Nov 09, 2007 7:20 am Post subject:
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Quote: | Take a look at the High Frequency VCO TH used in the SN-Voice to expo. control the tunable noise |
I'm not good enough to pull bits out of other designs and roll my own, but here goes: From Sheet 2; The 4046 plus the two opamps and transistors. Remove the gate circuit, add a trimmer to R4 for V/Oct trimming and replace R6 by a tempco? And probably better still, replace Q3/Q4 by a matched pair.
IC3d is just a current source, right? _________________ http://www.casia.org/modular/ |
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frijitz
Joined: May 04, 2007 Posts: 1734 Location: NM USA
Audio files: 54
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Posted: Fri Nov 09, 2007 9:12 am Post subject:
Re: VCO for Ken Stone's Wavetable |
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Etaoin wrote: | I'm looking for a VCO for my CGS Wavetable. So really the only requirement is that it tracks well in the higher octaves. It doesn't need to do anything else (no PW, FM, sync or whatever).
I've already seen the original Digisound design, but buying a CEM3340 just for this is a bit OTT. |
This one tracks perfectly up to 40 kHz:
http://home.comcast.net/~ijfritz/sy_cir4.htm
Ian |
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Nosferatu
Joined: Jul 27, 2007 Posts: 234 Location: Planet Rock.
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Posted: Fri Nov 09, 2007 9:22 am Post subject:
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What your asking for are a bit tricky to achieve, the longer the table the higher the frequecny is what gives, the 4046 are not very linear.
As Ian mentions triangle cores have a tendency to have good Hifreq range
and you can always squeeze out some additional range from these. |
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Scott Stites
Janitor
Joined: Dec 23, 2005 Posts: 4127 Location: Mount Hope, KS USA
Audio files: 96
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Posted: Fri Nov 09, 2007 9:25 am Post subject:
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Yeah, I don't think a 4046 will track all that well. I'd go for Ian's design. _________________ My Site |
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frijitz
Joined: May 04, 2007 Posts: 1734 Location: NM USA
Audio files: 54
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Posted: Sun May 11, 2008 7:07 pm Post subject:
Re: VCO for Ken Stone's Wavetable |
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Etaoin wrote: | I'm looking for a VCO for my CGS Wavetable. So really the only requirement is that it tracks well in the higher octaves. It doesn't need to do anything else (no PW, FM, sync or whatever). |
How high in frequency does this need to go? I've recently finished testing an ultrasonic vco that tracks within .07% over 11 octaves up to 120 kHz. Would this be useful? Plans right now are to incorporate this into a module with 10-step waveshapers (draw the waveforms with slider pots). But if there is enough interest I could do a separate board with just the expo converter and the oscillator core (pulse output).
Ian |
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andrewF
Joined: Dec 29, 2006 Posts: 1176 Location: australia
Audio files: 4
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Posted: Sun May 11, 2008 8:43 pm Post subject:
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I was thinking about building another wavetable recently and wondered about hooking it up to CGS bi-n-tic filter. That has the std. VCO input but has to run at high freq to operate the filter correctly. Connect a wire from the clock input of the 4024 (or one of the 4024 outputs) and run it to the wavetable VCO input.
if you are building, or have a bi-n-tic anyway, why not mate it it with a wavetable?
this is just an idea...any suggestions welcome |
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