Re: [AH] System 100M pot

From tonyallgood
Sent Fri, Apr 11th 2008, 11:46

 > is the a=log/b=lin thing a global standard, or just for Japanese parts?

Certainly for the ALPS and their clones A is log and B is linear. I 
don't think there is a global standard for pot markings, and if there is 
not everybody is using it. Most European manufacturers use B for log and 
A for lin. Spectrol and others have their own systems. Spectrol seem to 
use the suffix J for logs and nothing for linear.

The only way to tell for sure is to measure it. The quick and dirty way 
is to put the pot half way around and measure the resistance between the 
track ends and then the wiper and one of the track ends. If the second 
measurement is 10% or 90% of the full track resistance, its probably a log.

Other pot laws exist though, including log-log, reverse log and other 
bespoke laws, like for pan and fader controls on mixing desks.

Roland have a very groovy law for their bender pots from the SH series. 
They have a built in dead zone in the middle and once out of dead zone 
only need a small amount of travel to cover the whole resistance of the 

Some log pot tapers are better than others though. The Minimoog's log 
pots are different to ALPS types. The modulation wheel is particularly 
ineffective if replaced by another type of log pot.