[sdiy] Cheapest, simplest but still reliable VCO & VCA for polyphonic project

[karl dalen]

>> Also, consider if you really need lots of VCAs, look at stuff like the prophet 5 and memory moog, the modulation
>> sections of both are pretty complete, but also quite simple and require very few VCAs.
>Indeed.  Another example, the Siel Opera 6 I'm playing with at the moment uses one SSM2024
>quad VCA per voice and some >clever CV switching to give some useful modulation routings.
>As to George's point about SSM2164 VCOs, I would go the other way - use something else
>for the VCO (perhaps even, dare I say >it, a DCO), then a single SSM2164 would give you
>a 2-pole state variable VCF with CV-controllable resonance (2 VCAs for the filter, >1 VCA for the Q), and a VCA.

Some years ago when the SSM2164 was discussed i did just that, one 2164 for one voice in the spirit of ARP Chroma!
I.e one ota for VCO, 2 for a 2 pole SVF HP,LP and the last ota as VCA, For variable Q i used JX3 solution, back to back
transistors, itäs noisy solution but VCA mask's it. Controlled by a cheesy MSP40F1232. Idea was, take 30 of these and
make a Chroma! You need to compensate for the -3330PPM drift in the 2164. The whole hopla was slightely larger then
a stamp! Stamp synth SMD! No, i didnt finish it, programming skills and tool set was/is a drag! :-)

Reg
KD 


--- Den fre 2009-01-09 skrev Neil Johnson <neil.johnson97 at ntlworld.com>:

> Från: Neil Johnson <neil.johnson97 at ntlworld.com>
> Ämne: Re: [sdiy] Cheapest, simplest but still reliable VCO & VCA for polyphonic project
> Till: "synthdiy DIY" <synth-diy at dropmix.xs4all.nl>
> Datum: fredag 9 januari 2009 01.32
> Hi,
> 
> Paul Maddox wrote:
> >> Next question is in regards to the fact that since
> i'm doing a poly synth where one set of knobs controls
> all the voices, i'll have to make *every* parameter
> voltage-controlled, so i'll need a hell of a lot of
> VCAs. Any suggestions on good, cheap and very low
> parts-count VCAs? I'm guessing a LM13700-design.. ?
> > 
> > SSM2164 gives you 4 vca's in a single 16 pin
> package, BUT, they're AC only (IIRC).
> 
> No - DC coupled, so you could use then for CV mixing, as
> long as you want logarithmic mixing.
> 
> > Also, consider if you really need lots of VCAs, look
> at stuff like the prophet 5 and memory moog, the modulation
> sections of both are pretty complete, but also quite simple
> and require very few VCAs.
> 
> Indeed.  Another example, the Siel Opera 6 I'm playing
> with at the moment uses one SSM2024 quad VCA per voice and
> some clever CV switching to give some useful modulation
> routings.
> 
> As to George's point about SSM2164 VCOs, I would go the
> other way - use something else for the VCO (perhaps even,
> dare I say it, a DCO), then a single SSM2164 would give you
> a 2-pole state variable VCF with CV-controllable resonance
> (2 VCAs for the filter, 1 VCA for the Q), and a VCA.
> 
> Neil
> --
> http://www.njohnson.co.uk
> 
> 
> 
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy


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