I have received my 2nd D-6s this week (the DAC in the other room started to break down and simply was not worth getting repaired).
The D-6s is hooked to a small NUC Windows-PC (->USB), to a LS-Teufel streaming device (->Toslink) and to a Samsung DVBT2 TV-receiver via a small HAMA Toslink-SPDIF converter (->coax).
With the default DPLL setting (4) all sources play with no problem. I have not tried to decrease the value yet. Seems ESS has done a very good job designing the DPLL.
It's a nice feature that the D-6s memorizes all settings when the power is cycled; i.e. when it got switched of and on again, signal source, volume setting, etc. are in the same state like before. The unit even memorizes the power state. When you cycled power with the D-6s "on", it will be "on" when you reconnect power.