Analog or Digital volume

I seriously doubt it -- I have heard the Wadia, and they do not.

Is it a series or a ladder stepped attenuator? With a series, the signal goes through a lot of resistors and solder joints. I'm selling a CAT SL 1 III mostly because it uses a series stepped attenuator (as does the Cat Ultimate) and sounds much less transparent than an Accuphase DP 75 straight into power amps. And I thought Wadia's digital volume control was somewhat better than Accuphase's, though I haven't heard it. You should do only a little attenuation with a digital control, if you can manage that.

Alps make an excellent Conductive Plastic tracked Audio Potentiometer. Penny anf Giles in the UK also makes such a device, but very expensive. You could probably not get anything better than this. Digitally controlled stepped attenuators, or pure Digital attenuators relying on A/D and D/A converters with a DSP in between will not come anywhere a very high quality Conductive Plastic tracked analog potentiometer. Carbon tracked potentiometers are something else, they defenitely have a problem at zero crossing, as does carbon resistors, particularly at low levels.