My experience is different. I find just having a DAC on will do most of the burn in (67.354689%...he he). The current running through most components in a class A circuit is constant. This constant voltage and current will burn in most power supply capacitors (which take the most time to burn in). The signal path resistors, and filter caps, transistors and tubes and especially the output caps in a tube unit will need to have signal run through them to fully burn them in. But even the output caps in a tube DAC will have high voltage on them....helping them burn in without a signal moving through them.
Having a signal go through the DAC while it is on will improve the sound further but most of the burn in can be done by just leaving it on. You need to have a load on the DAC output when burning in and playing music...this way some current is being modulated through the output stage as it has a load to draw some current with. Just keep your preamp or amp off and play music. Your preamp/amp has a load resistance to ground that helps pull current from the DAC.
Having a signal go through the DAC while it is on will improve the sound further but most of the burn in can be done by just leaving it on. You need to have a load on the DAC output when burning in and playing music...this way some current is being modulated through the output stage as it has a load to draw some current with. Just keep your preamp or amp off and play music. Your preamp/amp has a load resistance to ground that helps pull current from the DAC.

