[Dublo7]

I've updated many of my flac files with their respective ReplayGain values. However, by a serendipitous turn of events, I noticed that when I remove those ReplayGain values from the tags, the files all of the sudden increase their gain and sound much better. They don't sound as flat as they did when the values were stored in the tags.

See for yourself;
Add a FLAC file to your Foobar playlist,
Right click that file > ReplayGain > Scan Per File Track-Gain
Once that has scanned, update the file tag. The value will now be stored in the file's tag.
Put on your headphones, listen to the file, and while you're listening, right click the file, go to ReplayGain once again, and click "remove ReplayGain info from file"

Strange, no?

Does anyone here know the reasoning for this?

 

[krmathis]

Well, isn't that exactly what Replay Gain is designed to do?
Lower the replay gain to match a loudness of 89dB, if the target file have a loudness higher than 89dB that is.

Replay Gain - Wikipedia, the free encyclopedia

 

[UNHchabo]

ReplayGain info tells Foobar to scale the volume of the file based on the tag. Since (based on your sig), you're using WASAPI, and probably not using any resampling DSPs, Foobar is taking your 16bit/44.1kHz files, scaling the output (usually down), and giving you different 16bit/44.1kHz data. Since Foobar has to throw out or round off some data in the process, you're getting less information than you started with.

Now, since it's been proven that louder sounds "better" in almost all cases, it's possible that the "flat" sound you heard is just in your mind, due to this psychoacoustic effect. It's also possible that you do, in fact, hear the loss of information from the volume scaling that Foobar's ReplayGain plugin is performing.

This has nothing to do with changing the tags; if you go to Preferences->Playback, and change the ReplayGain Source Mode to "None", it will sound exactly the same as if you removed the ReplayGain info from your files.

If you want bit-perfect playback when you're doing "serious" listening, but want to take advantage of ReplayGain when playing in shuffle mode, this plugin may help you:
foobar2000: Components Repository - Replaygain Override
You'll be able to turn on ReplayGain scaling for shuffle mode, so that adjacent tracks will be roughly equal in volume, while leaving ReplayGain scaling off for all other playback modes, allowing for bit-perfect playback.

 

[Redo]

I have replay gain values tagged in my entire collection, but I only let foobar adjust for the replay gain values when burning in headphones (to keep the burn in volume steady) and when having a mix of music playing through my stereo setup when company is over. Otherwise my volume knob finger is the replay gain =b