A mixer mixes many audio signals down to a stereo signal, just two channels, left and right. That is all. The role of the interface is to take analog audio signals and convert them to digital format - data (and vice versa for playback). You CAN simply go direct from your mixer's main outs into a stereo input on your computer - the soundcard in your computer will play the role of an interface and convert the analog stereo signal into two channels of digital audio, but it's not recommended. First, your computer soundcard is likely a piece of crap and will do a terrible job of this. It's designed to record and playback at low quality - youtube videos, your webcam, etc.. A proper interface will do a much, much better job. Like MUCH better. And second, your onboard soundcard is likely restricted to only two channels, i.e. a stereo input, whereas a proper interface typically has at least 2 inputs and outputs and can have many more. With more than two channels, you don't need to record things one or two channels at a time (especially important for recording a drumkit, for example, where 2 mics are a bare minimum and many people prefer at least 4). Once you have all these independent channels in your computer, you can adjust them individually, instead of just playing with the stereo mixdown from your hardware mixer, using a software mixer built into your software like Acid Music Studio (I assume it has one). So instead of working on tracks you've already mixed together using the hardware mixer, now you work on each of the individual tracks using your DAW. If you only record 1-2 tracks at a time anyway, you can technically get away with using the mixer and/or the onboard sound card, but again, the quality will be poor.

If you get a decent interface, the mixer is probably not needed at all. You could route one or two audio signals into your mixer and then into your computer directly, or through a better quality interface than your built in soundcard, but now the hardware mixer is basically redundant and just adding noise. More to the point, Behr(((#$#$#$ger mixers are very low quality and this extra step will just degrade the quality of the audio further. They are the noisiest pieces of crap I have ever had the displeasure to use.

Get a decent interface, skip the hardware mixer (unless you need it for headphone mixes for monitoring or something, and even then, I would try very hard to solve the problem in a different way), and have at er.

Good post, good reply.

Most interfaces have a headphone send for monitoring while tracking so naturally you can dispense with the mixer on that point.

Personally I like having a mixer at hand, my preference, something to do with the tactile response of the knobs and faders I suppose - having multiple discreet monitor sends, etc...