The log pot would always be for volume.

Log pots had a very gradual rate of increase in resistance as you turned it clockwise.


Logarithmic pots were typically used in volume controls for two reasons:

1) The log taper provided a finer control of listening volume at low levels, where users need that fine control, and

2) The log taper provides what is essentially a "dead band" at the low end of the pot, therefore accommodating the installation of an on/off switch on the back of the pot, without sacrificing low level volume control. The switch often requires a 15 or 20 degree rotation in order to activate -- using up part of the pot travel.

Interestingly, some of the aftermarket modular pot/switch manufacturers weren't that great about following those "rules" and when you installed such a replacement switch control into an old radio, the volume at switch activation was already too high for comfortable listening.