Without the DAC it's plugged straight into my motherboards on board sound through the 3.5mm to 3.5mm cable. While it does sound better than the speakers on my monitor I was expecting a whole lot more.
I thought it sounded kind of muddy coming straight from the on board sound. In addition it didn't sound anything too special but that's probably the result of me being spoiled by my DT990 600ohm and K702s and my taste in more aggressive fast paced headphones. To me the A2s sounded a bit too warm for my taste.
Then i found a spare RCA to 3.5mm cable from Monoprice laying around somewhere in my room and decided to hook it up and WOW what a difference. I was a bit skeptical at first but i guess it does make sense since the A2s already have a built in amp and my not so great computer on board sound acts as a DAC resulting in the poor SQ. After using the Bifrost as the DAC all my sounds became MUCH MUCH clearer with superior instrument separation, more microdetail, bass was not any stronger but did have more punch, soundstage increased slightly, and just an overall better listening experience.
One of my main test songs is *except i have it in FLAC and use Foobar*
Before the BIfrost DAC, there was no separation and everything sounded jumbled up together. At the 0.21 mark when instrument (not sure what it's called) kicks in it was very dissapointing to not be able to distinguish it's location. Mind you, not everyone may have the same experience though, the rest of the song was just a dissapointment to my ears.
After using the DAC i re-tested several songs and instrument separation was definitely better. For Counting Stars, instrument separation and soundstage increased quite a significant amount after using my own DAC. Right from the beginning I could hear instrument separation. Drums to the left, the shaking noise located to the far right, and the guitar right in the front.
Going to get myself a ODAC now as I don't want to spend another $400 on another Bifrost.