One thing I haven’t seen is the gain structure specs on the MU2 volume control/preamp. Is it passive, is there a buffer, or is there active/positive gain and, if so, then how much?
I believe most internal DAC/volume controls are passive. The manufacturers want buyers to believe that having sufficient output voltage is enough for good sound. Depending on the input impedance and sensitivity of the amplifiers, the cable length, and the owner’s sonic preferences, they may be right in some cases. However, there is a reason some of the DAC manufacturers offer small drive units with either active circuitry or transformers, and that is mostly for impedance management of the cables.
Considering the high’ish voltage output of most of today’s digital gear, I have been happy with a unity-gain buffer between my source gear and my amplifiers. Having the buffer interface with the amplifier restores the tonal richness and dynamics that some report missing when using purely passive volume controls, whether in a DAC or from a passive preamp.
