HappyWarlock wrote:
Is the software open ended to the signal it’s receiving?
The software is... but not the hardware.
The digital converter in the computer is 1) cheap, 2) subject to a storm of electrical bombardment from other components.
1) The computer's internal converter is convenient, and good enough for many applications. But the computer is built for general purposes, and its hardware isn't optimized (or budgeted) for sound quality. The converter you'd buy from a 3rd party is not only a better component, but is surrounded by better components that all conspire to make it sound better. The analog components in particular that are part of any analog to digital converter contribute hugely to the quality of the converted sound (and, sadly, the cost).
2) The insides of a computer are a hostile environment for raw audio. A raw analog signal that enters the computer is entering an audio battlefield, and by the time it reaches the converter and becomes a series of comparatively protected zeroes and ones, it may already have been battered and degraded by spurious noise. If you do the conversion outside of the computer - even using a cheap converter - the signal that enters the computer is protected by virtue of its conversion to a stream of numbers. Safely converted outside the computer, the audio can no longer be degraded by the analog storm that lurks within. Allow it to armor up in an external converter, and it enters in a fortified digital tunnel.
However, once it's converted, whether outside or inside the computer, as Hangtime suggests, Garageband won't in and of itself degrade the audio. Garageband is based on the same audio engine as the professional grade Logic. The fundamental audio engine is the same, so the audio quality should be the same.
That said, there's a number of ways you can make any audio sound terrible with software, in Garageband as well as in other applications. Key to maintaining audio quality is understanding how the software works, the concept of gain staging (to set levels correctly), minimizing the number of conversions you make (for example, if you convert a high resolution well-converted audio signal to an MP3 while you work, and then convert it to CD quality, you're still dealing with no better than the MP3 quality sound), and generally minimizing the amount of digital processes you run the signal through.
Digital processes can greatly enhance your work and engineers spend thousands of dollars on plugins to get their music sounding great. However, the more you mess around with the signal, the more the cumulative damage adds up. Kind of like adding too many spices to a recipe. Music that is well recorded, well converted, and minimally processed, tends to sound the most alive.
