From the link, it appears that to get 'lower' volume, you scale the output values if digital, whereas you may scale the output signal if analogue. If you have a

From the link, it appears that to get 'lower' volume, you scale the output values if digital, whereas you may scale the output signal if analogue. If you have an analogue output (stereo jack), then you probably generate a lower-power output and therefore save energy by turning the volume down. If you use digital out, then the volume of your local device doesn't have any bearing on the battery life of that device, because you are effectively putting out numbers. But I could be wrong!