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 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
VCO for Ken Stone's Wavetable
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Etaoin



Joined: Jun 30, 2005
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PostPosted: Fri Nov 09, 2007 5:38 am    Post subject: VCO for Ken Stone's Wavetable Reply with quote  Mark this post and the followings unread

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.

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softfin



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PostPosted: Fri Nov 09, 2007 5:53 am    Post subject: Reply with quote  Mark this post and the followings unread

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 Smile
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Etaoin



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PostPosted: Fri Nov 09, 2007 6:00 am    Post subject: Reply with quote  Mark this post and the followings unread

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.

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goldenechos



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PostPosted: Fri Nov 09, 2007 6:49 am    Post subject: Reply with quote  Mark this post and the followings unread

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



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PostPosted: Fri Nov 09, 2007 7:20 am    Post subject: Reply with quote  Mark this post and the followings unread

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?

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frijitz



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PostPosted: Fri Nov 09, 2007 9:12 am    Post subject: Re: VCO for Ken Stone's Wavetable Reply with quote  Mark this post and the followings unread

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

Very Happy

Ian
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Nosferatu



Joined: Jul 27, 2007
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PostPosted: Fri Nov 09, 2007 9:22 am    Post subject: Reply with quote  Mark this post and the followings unread

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
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Joined: Dec 23, 2005
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PostPosted: Fri Nov 09, 2007 9:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, I don't think a 4046 will track all that well. I'd go for Ian's design.
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frijitz



Joined: May 04, 2007
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PostPosted: Sun May 11, 2008 7:07 pm    Post subject: Re: VCO for Ken Stone's Wavetable Reply with quote  Mark this post and the followings unread

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).

Very Happy

Ian
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andrewF



Joined: Dec 29, 2006
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PostPosted: Sun May 11, 2008 8:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

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 Idea
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