I�m no audio electronics expert, but I know there are wholly analog circuits that can be used as volume controls where the audio signal is not run through an exposed resistive conductor with a sweeping arm moving along the conductor.

The digital operation of the 990 volume knob or remote control could, for instance, be converted to a controllable, steady analog voltage of say zero through one volt dc and then that dc voltage used to govern an analog circuit through which the audio signal is passed when in �bypass�. I don�t know if that�s actually the case, but it�s possible.