When using the analog output of the DLIII, it is not too hard to check that it's in "bypass" mode. The current mode isn't displayed continuously on the 990's front panel, but if you're not sure what the current mode is you can just press the "Stereo" button on the remote or the "Surr Mode" on the front panel (being careful to only push the button once, and assuming you are using firmware newer than the original 3.07) and the front panel will display the current mode. Unless you are in this mode, any evaluation of an outboard DAC will be nullified by the A/D/A conversion.