VCO for Ken Stones Wavetable-Modul

Boerge · Joined: Sep 02, 2009 Posts: 82 Location: Germany

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

fluxmonkey · Joined: Jun 24, 2005 Posts: 708 Location: cleve

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

forbin · Posted: Thu Aug 15, 2013 5:44 am Post subject:

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...

Boerge · Joined: Sep 02, 2009 Posts: 82 Location: Germany

forbin · Posted: Fri Aug 16, 2013 2:30 am Post subject:

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)

wmonk · Posted: Fri Aug 16, 2013 2:46 pm Post subject:

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

forbin · Posted: Fri Aug 16, 2013 8:15 pm Post subject:

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

Mongo1 · Joined: Aug 11, 2011 Posts: 411 Location: Raleigh NC

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

KnobHell · Joined: Jan 28, 2012 Posts: 56 Location: SLC

Where do you find the wave tables?

Boerge · Joined: Sep 02, 2009 Posts: 82 Location: Germany

forbin · Posted: Tue Aug 27, 2013 2:07 am Post subject:

I assume that you know about these?

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

KnobHell · Joined: Jan 28, 2012 Posts: 56 Location: SLC

Boerge · Joined: Sep 02, 2009 Posts: 82 Location: Germany

KnobHell · Joined: Jan 28, 2012 Posts: 56 Location: SLC

Awesome, thank you!

len