My O2 amp is connected to my Auzentech X-Fi Forte sound card. Usually I don't like heavily eq'ing my more expensive headphones, but lately I've been experimenting with it, primarily with the bass boost that's available in the console. I noticed that when I connect my headphone straight into my soundcard with the bass boosters and bass "volume" turned high the bass sounds full, powerful, and thunderous. Simply put, I haven't had this much fun listening to my bass-heavy music in a while.
When I connect them to my O2 with the bass on high, however, it gets distorted really easily. I can't even turn the bass up half way until the sounds starts to distort.
Normally I connect the 3.5mm to the line-out (green, front speakers jack), but when I insert it into the soundcard's headphone output I get the same volume. So I'm wondering: by connecting a external amp to my soundcard, is the distorting happening because it's essentially double amping? Is the sound card acting like a preamp? Why is it that the bass becomes so bad on the external amp when I increase it through the software?