What exactly is "0db" when recording? On my faders in garageband, I see things like -25db to 25db for the input signal. I know for panning, negative db is the left speaker and positive db is the right speaker, but what is it in terms of input signal? I've read things that have said that the signal begins to clip at 0dB. Is the +/- dB scale just a relative scale where it's something along the lines of, "This is how loud the input was, now you can boost it or lower it by _dB."

If that is the case, then how loud should the guitar be when you're actually recording?

Let's say that I have a mic up to my amp whose volume is set to 10. Then the unboosted "0db" signal will be loud. If I have the amp's volume set to 2 when recording, then the original signal will be quieter. Where does this factor in to "0dB" being where the signal begins to clip?
Last edited by kirbyrocknroll at Jul 7, 2011,
The db stands for decibels, the measurements of sound volume. As for "0 db", this is the loudest the signal can be before starting to clip (getting distorted, skipping and generally f@cking up the mix). When you record guitar, make sure the signal doesn't go above 0 db. Once it goes above, the sound starts to clip. It is generally recommended to record as close as possible to 0 db (but not above).

Hope that helps
think of the Level as "amount of sound" you let in while recording. 0 db is the pure, or "as is" sound you record. Anything below - less signal. Anything above - the "as is" sound gets boosted and distorted.
A good habit would be to record where the meter peaks in the the yellow on the loudest parts. With digital recording, you can always bring up the volume in mixing.