L.D. Moore - I noticed that too as my DAC has an external display which shows the locked signal sample rate. However, I asked around on various forums and it seems that the AudioMIDI sample rate changes when it's switched, but iTunes still locks on to the sample rate that was set upon the app's opening. So, AudioMIDI is up (or down) sampling from the iTunes locked in rate.
Apple 24 Bit 96 KhZ
With a new iMac 2.8GHz 10.5.5 OS how best to get 24 bit 96 KhZ? I have formatted the Audio Midi Setup to 96KHz 2Ch-24 bit. Can you play 2496 source music from the iTunes either through USB or Toslink/digital optical cable from the mini jack into a state of the art DAC - which is best audiophile?