Hi, a few years ago I talked to a guy who had installed something (I'm not very good with electronics) I think it was a different pot, that didn't roll off the treble if you lowered the volume. Does anyone have any idea what he was talking about?
There is really no such thing as not effecting the tone as you roll off volume.
That said - you can sort of compensate a little bit by using a small capacitor across the input and output of the pot. Try about 47picofarads as a starting point. Can also go to half or double that and see how ya like it... there's no set rule.