MP3 Doctor is an editing tool that lets you check, modify, and improve all your MP3s. You can repair imperfect songs or modify them with trimming, equalizing, resampling, normalization features, and more. The goal is to let you maintain a similar quality and sound on all your existing MP3s. In addition, it comes with encode and decode options.
More info:
hxxp://www.mp3software.com.ar/