[sdiy] CV inputs with bipolar "amount" knobs

[mark verbos]

On Jul 19, 2010, at 5:50 PM, David G. Dixon wrote:

>> If it's a DC thing: as I understand it the only problem is, the null
>> point is not exactly in the middle of the pot travel. Crude way to
>> take care of this: mount the knob on the pot shaft so that the
>> marking on the knob is in middle position at the null point.
>
> I believe Harry was talking about centre-detent pots, in which case  
> you
> can't really choose the centre independently.  However, if you use 1%
> resistors and a decent opamp, I can't imagine this should be a  
> problem.  I
> mean, after all, if you need absolutely zero CV to your circuit,  
> unplug the
> damn patch cord!  If that's not good enough for you, then a 1k  
> trimmer off
> one end of the pot will do the job; which end depends on where the  
> "true
> centre" is relative to the detent.


A trim pot in parallel with the pot is easier.

BTW. is there any reason to have the pot after the opamps rather than  
sending the signal through a resistor to the wiper and then one side  
to an inverter and the other side into the summer like Buchla does?

Mark