I use this DSP plugin for six years now to polish the sound quality of my MP3 collection when playing back. First in Winamp and now in MusicBee.
This plugin pretty much does the same thing that multiband compressors/limiters do for radio stations: Push music from different sources with different sound quality (too loud, too quiet, too much bass, not enough bass, too sharp, not enough highs and so forth) to the same level, so they blend smoothly when played together.
A good way to test is to search on SoundCloud for tracks and see how the plugin with the proposed settings here deals with the tracks and their various mastering qualities.
First download the DSP plugin:
http://www.stereotool.com/download/dsp_stereo_tool_installer_740.exeThen download the "Maximizer Dry" settings I use (the plugin is highly configurable, but the build in settings never applied to my taste - they distort more than enhancing and cleaning up the sound):
https://anonfile.com/F4qfl6feb5/Maximizer_-_Dry.zipThis settings file only uses the freeware options of the StereoTool plugin. There are also options that are only available when paid for. You can enable them (like a declipper or dynamic range enhancer) to check them out, but it will mix regularly occurring beeping sounds to the stream.
Copy the DLL from the installer and the .sts file to the plugin folder:
Open the DSP settings and load the preset file:
You can check out the before/after by toggling the Bypass button of the plugin:
If you want to tweak the sound to your liking (more/less bass, more/less highs and so forth), you can do it here (change the levels in the red circled soft limiter area):
You can change the strength of the compression/loudness here:
The strength of the stereo enhancement (phase amplifier) and channel separation (width amplifier) can be tuned here:
Have fun!
BTW: There are already newer version of the plugin available (8.x), but the "Maximizer Dry" settings are not 100% compatible and cause distortions.