> Hi,
> I have a 138-c too. I think there are two versions of this module, one

with

> linear response (for CV) and one with log response (for audio).

The A-138c is available only with linear response (you probably mix it up
with A-138a/b). Potentiometers with dual exponential response (symmetrical
from the center position) are hard to find. We asked our manufacturer if
this special response can be manufactured but they answered that it's not
possible (at least from them).

Best wishes
Dieter Doepfer