I believe that when you switch back and forth between the normal Stereo input, and Stereo Bypass mode, the outlaw display will show the incoming signal frequency for a couple of seconds. Connected to my player, the 950 will display 44.1 kHz with upsampling turned OFF, and 88.2 kHz with upsampling turned ON. Also, switching the upsample feature on and off on the CD player should provide audible evidence of it's presence. I would guess that if the S1500 upsamples the digital signal, that it's D/A section would process the upsampled signal and output this to the analog outputs. That is how my unit works.

Please let me know what you discover, as the S1500 is a unit I have been waiting to hear for a long time. It missed it's market delivery date by a margin that would embarrass even the Outlaws.

Allan