It's not 'bit rate' but 'bit depth'. What's your f/w version?
My D50 shows:
- DSD(64 for example) mode:
DSD64 2.82MHz 1Bit
- PCM 44100 (or higher) 24 bit / 32 bit (I'm unable to set to 16bit @USB connection):
PCM 44.1kHz (or higher) 24Bit (or 32Bit)
-PCM Redbook via optical:
PCM...