From the manual: "While in Standby Mode, the DAC1 USB continues to monitor the selected digital input and will immediately resume normal operation when an error-free signal is restored."
http://www.benchmarkmedia.com/sites/default/files/documents/DAC1-USB-Manual-RevG_0.pdf
http://www.benchmarkmedia.com/sites/default/files/documents/DAC1-USB-Manual-RevG_0.pdf