cordobaman
... to use an external DAC; the preamp's digital output feeds the input of the DAC, the analog output fro the DAC goes back to the analog input of the preamp, with control functions, including (hardware) volume from a tablet ...That's not going to work. What you need to do is connect the outputs of your digital source components to the digital inputs of your DAC, and then the DAC's analog outs to analog inputs on your preamp.