Hi Lara, what the others said but my extra 2 cents. Based on my experiences, my tracks seem to breath the best where the levels are conservative, and that starts when I record the source. It is said that most converters and plugins are working best with levels in a range somewhere between -14 to -18 digital full scale. When I start a mix of a typical rock/pop I'll usually start with the kick and snare peaking around -10, and actually thats about as hot as I record them. Then I'll make sure to adjust the levels into and out of every plug-in to keep them equal. I like to leave a lot of room on the master buss, then you can always raise it. When I'm pushing the digital 0 on the master early in the game, my mixes end sound choked and lifeless. Hope that helps.