Elektor Formant Modular

Hi everyone. Is there any easy way of adding cv to the freq of the LFOs in the formant?
Thanks:)

Just look at other VCO designs, it's usually a FET acting as a resistive control element or a Transconductance amplifier providing the current based variable control element.  Very easily done:

http://www.onsemi.com/pub_link/Collateral/NE5517-D.PDF
http://www.birthofasynth.com/Thomas_Henry/pdf/VCO-1/vco1_schem1.pdf

The only thing to be mindful of is if it needs to have a linear or exponential response, some offer both...

--- In ElektorFormant@yahoogroups.com, "abcceihgfosdjgooenje"  wrote:

>
> Hi everyone. Is there any easy way of adding cv to the freq of the LFOs in the formant?
> Thanks:)
>

Hi,

In case of Formant LFO, there's a clean and direct way for a linear voltage control mod. 
Referring to the original schema, A3 serves as a comparator, outputting +VDD and -VDD in alternation. These voltages serve as control voltages to deliver a current for integrator IC1 through P1.

So all to do is to supply an external control voltage, +CVext, invert it with an Op-Amp to create -CVext .
Then add a mux which is controlled by the comparator output and 
switches either +CVext or -CVext to P1. And you've got a linear controlled VC-LFO.

Good Luck.

--- In ElektorFormant@yahoogroups.com, "abcceihgfosdjgooenje"  wrote:

>
> Hi everyone. Is there any easy way of adding cv to the freq of the LFOs in the formant?
> Thanks:)
>

Im afraid im to much of a newbie to understand completely what you are saying.. Could you jot down a schematic on piece of paper for me, if you have the time? And be pretty explicit... im stupid;)
Thanks!

--- In ElektorFormant@yahoogroups.com, "haitar92"  wrote:

>
> Hi,
> 
> In case of Formant LFO, there's a clean and direct way for a linear voltage control mod. 
> Referring to the original schema, A3 serves as a comparator, outputting +VDD and -VDD in alternation. These voltages serve as control voltages to deliver a current for integrator IC1 through P1.
> 
> So all to do is to supply an external control voltage, +CVext, invert it with an Op-Amp to create -CVext .
> Then add a mux which is controlled by the comparator output and 
> switches either +CVext or -CVext to P1. And you've got a linear controlled VC-LFO.
> 
> Good Luck.
> 
> --- In ElektorFormant@yahoogroups.com, "abcceihgfosdjgooenje"  wrote:
> >
> > Hi everyone. Is there any easy way of adding cv to the freq of the LFOs in the formant?
> > Thanks:)
> >
>