QUOTE (saratoga @ Jun 21 2013, 18:09) <{POST_SNAPBACK}>
Transform codecs do not use integer sample values internally, no, but the output to the DAC is ultimately going to be an integer. If boosting the volume up +20 dB didn't add clipping, you've probably got the "prevent clipping" option enabled in your replaygain program.
I was applying the value to the file (= changing the file), not using a ReplayGain-enabled program to play them. I don't know how foobar handles that, perhaps it does prevent the audio from clipping but wouldn't that mean it won't be as loud as they were? The files were originally peaking at 0 dbfs and had values of around -5db if I remember correctly (before I edited the tags).
Edit: And if most portable players (be it dedicated players or cellphones, smartphones, etc) output in integer values, don't they truncate the peaks above 0db? If so it should have sounded terribly distorted, and it did not (well, not terribly). Interesting...