DAC break-in question

Yes you can. And for me , I have a Schiit Yiggy which needs to be warmed up and I leave it on continuously unless I’m gone on vacation. 

As @jl35 mentioned above, the DAC has no way of knowing what is connected to its outputs. It will try to spit out a signal even if nothing is powered up or even connected to its outputs. So you can definitely warm it up or break it in that way.

It seems to me that if you just let the music flow into the DAC, it could build up and when you eventually turn on the amp, the sudden surge of music to the speakers could overheat something or possibly even blow out the speakers (that makes as much sense as an electrical component needing break-in). 

So the answer is pretty simple -

running streamer into DAC (try to set up a playlist consisting of music with different bit rates and set it on repeat) without your amplifier on: you’re breaking in the digital in, power supply and the DAC section. You’re not breaking in the output section. To do a full end to end break in your amp or preamp that DAC is connected to has to be on. You can choose to break in the analog out section while listening and keep the digital front end running 24/7 with amp off and it will take a few days more. The digital section and power supply break in will be typically around 200hrs.
Or bite the bullet and keep the amp on for few days. When amp is off the signal from DAC analog out is not flowing. 

OK, so follow on question… do each of the inputs & outputs need to be burned in? IE: new pre… separate burn in required for phono line in, DAC in & HT in? Separate burn in for output to amp & headphones? Same question for a DAC, streamer in, CD in. How about each filter? I think the answer is yes, except perhaps the filters… but maybe even them. And then for how long? I don’t think my CD portion of my system will ever be burned in.