MP3 Amplifier lets you seriously boost you music's audio, but it does take a little while to work. Since the app doesn't sacrifice the quality of the audio when it amplifies it, it's definitely worth the wait. It even has a very attractive layout, making it a good app to have if your smartphone or tablet's speakers don't sound fantastic.
This app lets you pick how loud you want your song to be with a basic sliding scale. It goes from one to ten, but pushing it further than seven isn't recommended. The app lets you know this by turning the text red, which is handy. MP3 Amplifier can amplify files in bulk, but a four-minute track took about one minute to convert. If you plan on doing an entire album, you might want to have something else to do while this application works its magic. MP3 Amplifier doesn't ruin the track's audio in the process of making it louder, which is a pleasant surprise. Instead of amplifying your original file, this app creates a copy of the file you want. That's helpful, but it can drain your storage quickly. The app doesn't let you change where it saves files, either.
If performance is one of your main concerns, you're not going to find a more rock-solid app than MP3 Amplifier. Just be patient with it when it's actually converting your files.