[sdiy] OTA VCA

[cheater00 cheater00]

Hi Elain,
It just depends on whether your AR has exponential or linear output. Linear
into linear might not sound the way you'd like it.

On Mon, 20 Mar 2017 16:58 Elain Klopke, <functionofform at gmail.com> wrote:

> So I'm going to put this can of worms on the table and back off slowly
> before opening it....
>
> Due to various reasons (not the least of which was getting shafted by the
> person  I purchased a large quantity of LDRs from) I'm switching over to an
> AR envelope generator and VCA combo for keying my notes on the paraphonic
> synth.
>
> I decided to go with some circuits that I know and have assembled a few
> times, the AR generator and VCA from Ray Wilson's original Sound Lab mini
> synth. I'm going to try to trim away the bits of the AR generator that have
> to do with the triggered mode since these are going to be gated by the key
> presses only and see if they still work.
>
> Question time: Ray's VCA is a simple half-a-LM13700 with the CV going into
> the Bias input and the op amp bit doing its amplify-y thing.
>
> 1) In his notes, Ray talks about the response to the CV being linear.
> Since I'm just using this to switch the notes to the rest of the synth with
> a little preset attack and release that shouldn't be a problem, right? It
> would only do strange things if I tried feeding it an exponential envelope
> from an external source?
>
> 2) If I hard-wire the initial gain "knob" to no initial gain, it's going
> to be silent until the envelope hits it?
>
> 3) Is there any noticeable difference between an LM13700, NJM13700, and
> NJM13600 besides the price? Because at 148 chips for a 3-octave keyboard,
> price is kinda a thing.
>
> -Ian
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