Doepfer

Whether you choose 25k, 50k, or 100k, the pot will give the same
linear relation between the input and output voltage (linear as a
function of the variable resistance).  So is there some
in-the-actual-world difference between the resistance values, that is
not covered by the idealized Ohm's Law?

Monroe

Hi Monroe

There can be a difference between values due to the load resistance that the wiper connects to. If you have a 100k pot that has 100k load on the wiper (e.g. for a linear mixer) then the overall resistance of the pot falls to 50k at the top but at 50% position the wiper should have 50k above and 50k below on the pot but the 100k only loads the bottom half giving 50k at the top and 33k at the bottom. The 50% position is now the 40% position.  In other words you can change the law of a pot from linear to something approaching a log depending on the values you use.  Ideally to retain the linearity the load needs to be much greater than the pot. You can change a linear pot to a log pot by loading it with about 20% of the pots value. There are lots of tricks that can be played with loading the bottom half or the top half even - try googling 'potentiometer law change'.

Hope that lengthy explanation answers your query
Regards
Tony


--- In Doepfer_a100@yahoogroups.com, Monroe Eskew <monroe.eskew@...> wrote:

>
> Whether you choose 25k, 50k, or 100k, the pot will give the same
> linear relation between the input and output voltage (linear as a
> function of the variable resistance).  So is there some
> in-the-actual-world difference between the resistance values, that is
> not covered by the idealized Ohm's Law?
> 
> Monroe
>