Crooked Sidewalks wrote:Reply to part one; USB is almost automatically better than the sound card. The data transfers faster, allowing for higher quality.
That is not at all how it works. USB is a digital signal, the headphone jack is an analog signal - there is no "data" in an analog audio signal, just analog audio. Getting an audio interface just moves the job of converting analog audio into digital data from the internal sound card (decent at the job) to an interface) hopefully much better at the job).
The issue here is impedance matching - a prosounded gameboy outputs at line level-ish, and your Apple laptop's audio input is designed to recognize the difference between line level and mic level. Long boring technical story short, I do quick demos of gameboy tracks by plugging prosounded (or even unmodded headphone) jacks into my laptop's sound in all the time. It sounds totally passable, and yours should to.
When I do serious recording of the game boy, it always goes through an audio interface, and there is a noticeable improvement in bass response and clarity which I find most necessary when combining the resulting signal with other signals.
My recommendations:
1. Try recording without the mixer (straight into the jack) and see what happens. You may very well be fucking something up with that mixer in line. If you can get it to sound halfway decent without the mixer, then try working the mixer back in. You haven't really given any details on how you are plugging the mixer in, so hopefully you aren't using the headphone output or something like that.
2. Eventually buy an audio interface; if all you can afford right now is that Behringer thing, wait. You need to get something that will actually do a better job than your internal sound card. Save up a couple hundred bucks at least.