There are many alternatives to MP3Gain for Mac if you are looking to replace it. The most popular Mac alternative is 
QMP3Gain, which is both free and Open Source. If that doesn't suit you, our users have ranked 15 alternatives to MP3Gain and five of them are available for Mac so hopefully you can find a suitable replacement. Other interesting Mac alternatives to MP3Gain are 
iVolume (Paid), 
MP3 Normalizer (Paid), 
MP3Gain Express (Free, Open Source) and 
ppmBatch (Paid).
A free automatic mp3 volume normalizer. MP3Gain analyzes and adjusts mp3 files so that they have the same volume. If you're looking for more info about MP3Gain like screenshots, reviews and comments you should visit our info page about it. Below you find the best alternatives.
Graphical user interface front end supporting MP3Gain engine which analyzes and losslessly adjusts mp3 files to a specified target volume. A complete re-creation (made in QT4) of the original MP3Gain GUI, however it can be run on more platforms.
iVolume calculates the volume perceived by the human ear for each song of your iTunes music collection. Thereby it gets the most out of the approved Replay Gain algorithm and adjusts your songs accordingly. It integrates seamlessly with iTunes on Mac & PC, iPod, iPhone, Apple TV, FrontRow and AirTunes. Most popular audio file formats like MP3, M4A/AAC, AIFF and Apple Lossless are supported.
MP3 Normalizer improves the quality of MP3 files. It amplifies too quiet audio or decreases the volume of too loud files or their parts automatically. It also smoothes sound peaks and clicks in MP3 tracks. MP3 Normalizer can make voice records more hearable with the Special processing of voice feature. Audio effects, such as trimming of silence at the start and end of tracks, applying Fade-in and Fade-out effects smooth switching between tracks and improve the listening experience overall.
MP3Gain Express is a basic port of MP3Gain to Mac OS X. It allows you to analyze or apply track gain to a list of MP3 files. Anyone who has used the Windows UI for MP3Gain should find this one familiar, as it was designed to look similar to that version. It's easy to use. Simply select the files you want to increase or decrease the volume of, enter the desired loudness, and click Apply Gain to update your files.
ppmBatch allows you to analyze and normalize your audio files according to various broadcasting loudness standards. It batch processes files in multiple real time and provides intuitive user feedback about each file's compliance status and processing progress. Measurement results are displayed in a clearly arranged, customizable user interface.
