I have some music tracks which were ripped from a CD to WAV files initially. I wanted to increase the loudness\amplification to fit in with other music I have and used the Limiter with the following settings: Input Gain (L & R) +2.0, Limit to (-10.00), Hold (10), Apply Make-up Gain (YES). After this I went to Effect\Amplify and applied Amplification of -0.5 to give some head room for when they were converted to M4A files (via iTunes).
I generally only listen to this music via my PC speakers or iPod and these tracks seem to play back fine.
What I am wondering now is if (from a quality of output point of view) I would have been better off using the Limiter with NO Make-up Gain and increase the Input Gain to approximately +5.0 to give me a similar desired increase in loudness\amplification ? The settings to do this would be: Input Gain (L & R) +5.0, Limit to (-0.5), Hold (10), Apply Make-up Gain (NO).
The original way I did it involves 3 separate operations: Input Gain, Make-up Gain and then negative Amplification. Is that detrimental to the quality of the output compared to the quality of the output I would get from using the No Make-up Gain and extra Input Gain method or doesn’t it make any difference ?
Amplifying (higher or lower) has virtually no affect on the quality other than making the waveform bigger or smaller, provided that the waveform does not exceed 0 dB for integer format tracks. Audacity uses “32-bit float” format tracks by default, which can handle “over 0 dB”, but most export formats, and virtually all sound cards cannot go above 0 dB.
The “makeup gain” in the limiter attempts to bring the peak level up to 0 dB. However, for efficiency, it only approximates. If you require an exact 0 dB, use the Amplify effect.
Note also that some export formats (“lossy compressed” formats, such as MP3) produce an approximation of the sound. The peak level after exporting may be a bit different from the original waveform. This is particularly true for audio that has been heavily compressed / limited, as the encoding process will tend to overshoot the squashed peaks. To avoid clipping, it is necessary to allow a little headroom before exporting. (a surprising number of commercial recordings are slightly clipped).