[sdiy] center tapped pots?

[Dave Manley]

Andre Majorel wrote:
> On 2007-04-10 19:20 +0100, Mike wrote:
> 
>> There is an old trick I learned back in the day, to get a 'dead
>> band' in the middle of a pot: connect a pair of diodes, back to
>> back, in parallel, in the line from the wiper. This gives a +/-
>> 0.7V mid point null area. It can be useful, for for pitch
>> benders, since the voltage from the pot is being added to the
>> pitch voltage anyway.

For reference, this method is used in the ARP pitch-bend circuits.

> 
> Or as shown below, run two resistors of equal value from the
> wiper, one going to the CW lug, one going to the CCW lug. The
> curve is relatively flat around the mid point and gets steeper at
> either extreme. Probably good for a VCO detune pot.
> 
>   http://www.elby-designs.com/documents/tailoringpotentionometers.pdf
> 

This is a good paper, but the warnings in the last paragraph should 
perhaps be put at the start: the resistance across the pot with the 
extra resistor(s) can be much lower than the original pot depending on 
the curve you're trying to achieve.  As they say in the paper: the 
surrounding circuit may not like this much.

-Dave