Digital passthrough means that the Squeezebox will output the DTS encoded bitstream via it's S/PDIF output. The squeezebox will not decode the bitstream to analog itself. You'll then need a DTS decoder downstream from the squeezebox- typically a home theater reciever to decode it to something listenable. If the analog output is active when playing a DTS stream (not sure if it is or not) the undecoded signal sounds like high level pink noise.