[sdiy] 4-Quadrant VCA?

[Tom Wiltshire]

There’s are examples in Ray Marston's Audio IC user’s handbook with both CA3080 and LM13700 - both very similar:

https://www.scribd.com/document/253630610/Audio-IC-s-Users-Handbook-Marston-pdf

I have to agree with David D. though - this is better done with the 2164. You’ll get a better result. The feedthrough and distortion on the LM13700 means it’s always a high to get it “good enough”.

2 cents,
Tom

==================
       Electric Druid
Synth & Stompbox DIY
==================

> On 13 Sep 2017, at 20:54, Olivier Gillet <ol.gillet at gmail.com> wrote:
> 
>> I know I could use AD633s but they are really pricey. Any other clever ways
>> of pulling this off?
> 
> Add enough DC offset to one of the signals to make it unipolar.
> Subtract the other signal from the result. Choose wisely which branch
> of your circuit is labelled as the "control" path and which one is the
> "audio" path.
> 
> https://forum.mutable-instruments.net/t/blinds-how-does-it-work/8287
> https://mutable-instruments.net/modules/blinds/downloads/Blinds-v60.pdf
> 
> Pros: no distortion, no odd behaviour at zero-crossings, doesn't cost
> more than a normal VCA circuit.
> Cons: need a couple of precision resistors, non-ideal behaviour at
> high frequencies.
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