[sdiy] Multi-source crossfader

[Kyle Stephens]

Funny this comes up, as I got on the topic of vector synthesis (mentioned on one of JH's scanner project pages) a few days ago.

I picked up an old motor speed controller at a surplus shop a while back - it's got a nice sloped case, about 12" x 8", with a center-returning joystick in the middle. I gutted out the board and was left to wonder how to best make use of it. After some "research" (see: Wikipedia jumping), the idea of shuffling through wavetables sounds like a great way to wring the most variety out of the two axises of a joystick, a la vector synthesis, ie: the Sequential Circuits Prophet VS.

Apart from reading up on the Prophet VS and its vector interface, I've looked at some existing DIY implementations of wavetables, namely those of Ken Stone (http://www.cgs.synth.net/modules/wavetable.html), and Keith Winstanley (http://home.freeuk.net/lowpass/VCDO.html). There's a .zip available on Keith's page of the original Digisound VCDO module from which both are based.

I'm curious about what kind of modern upgrades could applied to this kind of design. 64-bit eproms would be a bit overkill, but even trying a 16-bit would have some more room for variety with the wavetables (versus the original 8). If I want to get back to that lofi character, I could just drop address lines into the DAC. And if nothing else, a newer eprom would suck less juice - the ones prescribed for the Digisound one took up to 500mA (yes, half an amp!).

All this being said, I get the general theory of the process, less so the specifics of implementation. I've been tackling the VS service manual (http://www.retrosynth.com/docs/pvs/), and some of National Semiconductor's application notes on DACs - any other suggested reading?


It's interesting that I pass by Sequential's address listed in the service manual (3051 North First Street, San Jose, CA, USA) on my way to school :3

And Google Maps says Sequential still has a space there:

http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=3051+N+First+St.,+San+Jose,+CA,+usa&sll=37.394539,-121.934209&sspn=0.007825,0.013819&g=3051+N+First+St.,+San+Jose,+CA,+usa&ie=UTF8&ll=37.396107,-121.934187&spn=0.007825,0.013819&z=16&iwloc=r0


_Kyle


--- On Tue, 2/3/09, JH. <jhaible at debitel.net> wrote:

> From: JH. <jhaible at debitel.net>
> Subject: Re: [sdiy] Multi-source crossfader
> To: elektrodwarf at yahoo.se, synth-diy at dropmix.xs4all.nl
> Date: Tuesday, February 3, 2009, 11:18 PM
> http://www.jhaible.heim.at/interpolating_scanner_and_scanvib/jh_interpolating_scanner_and_scanvib.html
> 
> JH.
> 
> ----- Original Message ----- 
> From: "Karl Ekdahl" <elektrodwarf at yahoo.se>
> To: <synth-diy at dropmix.xs4all.nl>
> Sent: Tuesday, February 03, 2009 10:44 PM
> Subject: [sdiy] Multi-source crossfader
> 
> 
> Hi list, i'm in need of a multi-source crossfader,
> specifically i'm going to 
> have a fader going inbetween four waveforms (square, saw,
> tri, sine). I 
> started designing some kind of BTJ-contraption but figured
> perhaps someone 
> here already made one?
> 
> Thanks
> 
> Karl
> 
> 
>      
> __________________________________________________________
> Ta semester! - sök efter resor hos Kelkoo.
> Jämför pris på flygbiljetter och hotellrum här:
> http://www.kelkoo.se/c-169901-resor-biljetter.html?partnerId=96914052
> 
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> 
> 
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy