[sdiy] CV inputs with bipolar "amount" knobs

[Tom Wiltshire]

Thanks everyone.

The Fonik design and the EFM VCA5B design are basically the same; a differential amp fed with one signal. One thing I don't understand though - they used 47K/47K for the inverting feedback, but a 50K pot for the non-inverting feedback (essentially a 25K/25K split). Just for the symmetry of it, I'd have wanted to use a 100K pot here. Can anyone think of a reason why I shouldn't?

Thanks again,
Tom

On 19 Jul 2010, at 15:00, bbob wrote:

> i think, check out the first section of fonik's dual voltage processor:  http://modular.fonik.de/pdf/dual%20voltage%20processor.pdf
> 
> On Mon, Jul 19, 2010 at 9:24 AM, Tom Wiltshire <tom at electricdruid.net> wrote:
> Hi All,
> 
> I know various people have built various devices with CV inputs that have bipolar "amount" knobs so that you can easily invert a CV input - particularly useful for envelopes and such like.
> 
> How many different ways of doing this are there? Can anyone provide a reference to a schematic online?
> 
> I just had a big hunt around thinking I'd find loads, but mostly they must be parts of other circuits 'cos I couldn't find any.
> 
> Any pointers appreciated.
> 
> Thanks,
> Tom
> 
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