What internal sampling rate do you use?

We use a 48 kHz internal sampling rate. We made this decision for two reasons: (1) almost all mastered recordings are made in 48 kHz, so while upsampling these doesn’t hurt the original signal at all nothing is really gained by artificially doing this, (2) 48kHz allows the modern DSP processing (e.g. frequency filtering, bass enhancement, speaker current mointoring) we used in our designs. The argument for using a higher sampling rate like 96 kHz is that it is easier to make the final DAC output filters (which must be analogue) at because they can have shallower slopes. We believe we have made superb output filters for the 48 kHz signals so in the end using 48 kHz was a better choice for us.