[sdiy] lots of VCAs on one PCB

[Oscar Salas]

--- On Tue, 11/24/09, Derek Holzer <derek at umatic.nl> wrote:

> From: Derek Holzer <derek at umatic.nl>
> Subject: Re: [sdiy] lots of VCAs on one PCB
> To: synth-diy at dropmix.xs4all.nl
> Date: Tuesday, November 24, 2009, 11:52 AM
> Thanks to everybody who replied so
> far! I'll try to run down the possibilities so far in this
> email:
> 
> 1) Oscar Salas: "Tessera" quad VCA
> 
> I initially looked at Marc Bareille's Quad VCA, and I would
> have to pass on this VCA setup for the same reason. It needs
> too many PCBs. I use a fairly shallow case and mount all my
> boards parallel with the faceplate. There would not be room
> for four (or eight!) PCBs stacked up, especially considering
> the space needed for the joysticks, jacks and pots behind
> the board as well.
> 
> 2) Kyle Stephens / Gergo Palatinszky / Andreas Wetterberg
> 
> Four seems to be a common number when dealing with groups
> of joysticks (see Tessera, Bareille's Quad etc etc. The THAT
> 2181 looks interesting, however I specifically mentioned
> using it for control voltage and this one is exponential.
> 
> 3) Mark Verbos
> 
> 4049 hex VCA looks great from the angle of low parts count
> and cheap. Heck, with SMD it would be almost
> microscopic!!!!! I just wonder how it sounds? I wouldn't be
> using it for audio rate modulation, however some of the
> gestural stuff with the joystick could get pretty fast.
> Anyone know how well this VCA design sounds?
> 
> 4) Tim Parkhurst / John Mahoney
> 
> The SSM2164 was indeed the first chip I looked at, and yes
> it is exponential. My other joystick based project is in
> fact a quad spatializer, and nothing could be easier than to
> use 8 2164 ICs and be done with it. The fact that they must
> be doubled to get a linear response adds quite a bit of
> board real estate to the problem, and is basically the same
> as the Tessera that Oscar mentioned, and the same as
> Bareille's Quad VCA. If I could find a board layout small
> enough (my Eagle/Kicad skills are very poor) then I would
> certainly consider such an option. Ideally, I'd love it if
> someone with better PCB laypout skills than me wanted to
> take either the Tessera or the Quad VCA and SMD-ize them
> ;-)
> 
> 5) Jason Proctor
> 
> I'm trying to avoid any digitization of the signal for the
> moment. Programming too. I got into analog synths to get
> away from digital music (Pure Data programming mostly).
> However I'll keep it in mind.
> 
> 6) Kyle Stephens
> 
> The SSM2024 also looks interesting, however the first thing
> that the Bergfotron page you directed me to says is that the
> performance is quite poor. Too bad, a single IC with four
> linear VCAs would be a good solution!
> 
> 7) Nathan Trites
> 
> Two boards of 8 would be just fine with me. I figure that I
> have room for two PCBs "under the hood", but not four. If
> you were interested to help with this project, let's talk!!
> 
> Best!
> Derek
> 
> --::: derek holzer ::: http://blog.myspace.com/macumbista ::: http://www.vimeo.com/macumbista :::
> ---Oblique Strategy # 140:
> "Reverse"
> 
> 
> 
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