The ''loudness" knob is indeed just a controller of a digital circuit in some equipment. However the actual volume can be controlled in a number of ways. One is to scale the digital to analog converter mathematically. Another approach is to control a resistive 'ladder' network where turning the control shunts in precision resistors in the analog signal path, thus attenuating the signal. How the 950 does it is anybody's guess. Many ways to try to get an errant Norton to start up....I mean to attenuate a signal.