AudioRefurb

AudioRefurb is a program designed to help you improve the quality of your sound files by applying various types of audio effects and filters.

The utility features a straightforward interface, comes with a built-in audio player, and enables you to create your own sound presets and save them for later.

All you need to do is to import the sound file you wish to edit, select the preferred type of controls (Distortion, Filter, Delay, etc.), and configure the audio settings according to your needs. In the trial version of the program you can complete all of the aforementioned steps, but you cannot export the end result. So, you can't be 100% if the quality is preserved and which are the supported output formats.

Another thing that bothers me about this tool is that it doesn't offer you support for formats like OGG or FLAC. It also occasionally runs slow (when importing sound files, configuring output settings, etc.). My guess is that the program might not work smoothly because it's not ready for my macOS version (10.12). The download URL from the homepage of the developer gives you access to 2 program executable files: one is for Snow Leopard (10.6 Mac OS X) and another is for Lion and Mountain Lion (10.7 and 10.8 Mac OS X). I used the latter.

In my opinion, you should first see how the utility works on your Mac and then decide if it's worth buying it.