Change the level of an audio file by a fixed amount in decibels. The gain runs from -24 dB to +24 dB, and the same value applies to every channel so the stereo image does not shift.
Decibels, not percentages
Audio level is measured logarithmically. Each 6 dB step doubles or halves the amplitude of the waveform:
+6 dBdoubles the amplitude+12 dBquadruples it-6 dBhalves it0 dBleaves the samples untouched
Perceived loudness is a separate scale. Doubling amplitude does not sound twice as loud; a change closer to 10 dB usually does.
Clipping above 0 dBFS
Digital audio has a ceiling. Samples are stored in a range that peaks at 0 dBFS, and anything pushed past it has nowhere to go. On export those samples are clamped flat, which replaces the top of each waveform peak with a straight line and adds harsh upper harmonics.
A track already mastered near 0 dBFS has no headroom, so even +1 dB will clip it. The peak and RMS meters next to the transport show where the level sits while the file plays.
Comparing against the original
The bypass control in the transport swaps between the processed and unprocessed signal at the same playback position. Since a level change is the easiest thing to mistake for an improvement, switching back and forth is the fastest way to judge whether the gain is doing what you want.
Re-encoding the same format
The export comes back in the container the file arrived in, at a bitrate read from the source, so a level change does not quietly turn an MP3 into a WAV or inflate a 96 kbps file. Changing format is the Audio Converter’s job.
That does mean a lossy source goes through its encoder once more, and each pass discards detail that cannot be recovered. Convert to WAV or FLAC before the level change when the file still has several edits ahead of it.