Pots wear and log pots don't track particularly well.
The problem with stepped pots in passive preamps is they need to be mated to the driven device. When the input impedance changes, so does the taper. If the R values are adjusted to provide accurate steps with a given impedance, 1db steps are fine. Adjust for amp gain and speaker efficiency as necessary. See http://ielogical.com/assets/Audio/PassiveLC1.png for how to adjust. PM if you need more assistance.
The problem with stepped pots in passive preamps is they need to be mated to the driven device. When the input impedance changes, so does the taper. If the R values are adjusted to provide accurate steps with a given impedance, 1db steps are fine. Adjust for amp gain and speaker efficiency as necessary. See http://ielogical.com/assets/Audio/PassiveLC1.png for how to adjust. PM if you need more assistance.