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 Forum index » DIY Hardware and Software
VCO for Ken Stones Wavetable-Modul
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Boerge



Joined: Sep 02, 2009
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Location: Germany

PostPosted: Tue Aug 13, 2013 3:35 am    Post subject: VCO for Ken Stones Wavetable-Modul Reply with quote  Mark this post and the followings unread

Is there any discrete VCO suitable for Ken Stones Wavetable-Module?

(This one: http://www.cgs.synth.net/modules/wavetable.html )

I know that it is based on the Digisound-VCDO, which uses a CEM-VCO. I would like to make a discrete VCO (I got no CEMs Sad ), but which circuit would be fast enough? The frequency needs to be 64 times higher than the played key...

regards

Boerge

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fluxmonkey



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PostPosted: Wed Aug 14, 2013 5:39 am    Post subject: Reply with quote  Mark this post and the followings unread

https://sites.google.com/site/hearnmorley/products/hmvco1b
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forbin



Joined: Jan 29, 2009
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PostPosted: Thu Aug 15, 2013 5:44 am    Post subject: Reply with quote  Mark this post and the followings unread

ideally you need a vco that is running about x256 or so of the frequency you want -- maybe the Thomas Henry x4046 with a smaller capacitor/Ian Fritz's Double Decka Core/Tim Sinchcombes SCF VCF's oscillator...
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Boerge



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PostPosted: Thu Aug 15, 2013 11:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

forbin wrote:
ideally you need a vco that is running about x256 or so of the frequency you want


Why 256? Each waveform has 64 bitpatterns in the ROM, so 64x higher frequency should be enough. But as you mentioned the 4046: how is the settling time (? find no better word Wink ) of a 4046-PLL? Could one use a normal VCO and multiply the frequency by 64 with the PLL? Or would be a audible delay (or something like portamento) there?

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forbin



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PostPosted: Fri Aug 16, 2013 2:30 am    Post subject: Reply with quote  Mark this post and the followings unread

your right about the 64 step waveforms -- i was pretty sure that they were 8 bit wide but that as a newer wavetable vco -- you are still going to need a pretty high frequency vco though... if you want to go to 18kHz or so then you are going to need around a 1MHz -- you could try and phase lock but as you predicted you would get some slight glitchiness on transitions -- Thomas Henry's x4046 is actually a nice VCO and tracks pretty well -- see http://electro-music.com/forum/topic-42721-75.html at those frequencies you might want to loose all the bits hanging off the capacitor though as i suspect the input capacitance of the TL084 would start to be a consideration (the bits that generate the triangle/sawtooth waveform -- which you don't really need in this application anyway)
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wmonk



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PostPosted: Fri Aug 16, 2013 2:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

What about the core of the Ian Fritz DoubleDeka? That one has a higher frequency too. Smile
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forbin



Joined: Jan 29, 2009
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PostPosted: Fri Aug 16, 2013 8:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

Oh that's true. It uses that slightly freaky Voltage to Frequency chip from NatSemi (well TI now, if they haven't discontinued it...)
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Mongo1



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PostPosted: Tue Aug 20, 2013 12:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

I may be wrong, but you might also be able to use the Fritz Teezer core. That thing has quite a good range on it!

Earlier you asked if you could use a regular VCO and the use the 4046 to phase lock to it. I think the short answer is 'no' - it would require a very wide range, and really complicated loop filter.

Gary
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KnobHell



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PostPosted: Mon Aug 26, 2013 8:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

Where do you find the wave tables?
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Boerge



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PostPosted: Mon Aug 26, 2013 10:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

KnobHell wrote:
Where do you find the wave tables?


Oh, that was a bit tricky Wink I searched for the original Digisound ROM image, and found it long ago somewhere in the web. And I remember a website too, where you could make your own patterns, directly on the site or via downloading a little tool for that. I must dig in my archive Wink

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forbin



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PostPosted: Tue Aug 27, 2013 2:07 am    Post subject: Reply with quote  Mark this post and the followings unread

I assume that you know about these?

http://www.adventurekid.se/akrt/waveforms/adventure-kid-waveforms/
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KnobHell



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PostPosted: Tue Aug 27, 2013 8:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

forbin wrote:
I assume that you know about these?

http://www.adventurekid.se/akrt/waveforms/adventure-kid-waveforms/


No, I'll check them out.

Thanks
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Boerge



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PostPosted: Fri Nov 08, 2013 3:47 am    Post subject: Reply with quote  Mark this post and the followings unread

KnobHell wrote:
Where do you find the wave tables?


Found it, finally Wink

http://www.synthfool.com/docs/Digisound/

Greetings

Boerge

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KnobHell



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PostPosted: Sat Nov 09, 2013 9:24 am    Post subject: Reply with quote  Mark this post and the followings unread

Awesome, thank you!

len

Boerge wrote:
KnobHell wrote:
Where do you find the wave tables?


Found it, finally Wink

http://www.synthfool.com/docs/Digisound/

Greetings

Boerge
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