My Mac is running Mojave v. 10.14.1 and Audacity is v. 2.3.3. I just can’t decifer how to use the “Amplify” effect. There are two boxes which accepts numerical inputs. The top box is labeled Amplification (db) and usually has a value present upon opening. Let’s use 3.522 as an example. Firstly, is that to be understood as -3.522 db or +3.522 db. The second box is labeled New Peak Amplitude (db). Secondly, lets say a particular track sounds appropriate in the mix with it’s gain slider set to -3 db (less than 0 gain) with the other tracks set to 0 on their gain sliders. What value to I enter and in which box to establish that amount gain for that track with the track gain slider set to 0 db rather than -3 db?
The top box is labeled Amplification (db) and usually has a value present upon opening. Let’s use 3.522 as an example. Firstly, is that to be understood as -3.522 db or +3.522 db.
Just like everyday numbers, it’s positive unless there is a minus sign. 
A positive value is amplification and a negative value is attenuation (volume reduction).
The default value is the the up-or down change needed for 0dB peaks. (0dB is the “digital maximum”.*) Adjusting for maximized peaks is called “normalization” (although the Audacity Normalize effect adjusts-to -1dB by default).
The New Peak Amplitude allows you to “normalize” to a different peak level. If you don’t allow clipping this value will always be zero or negative.
As you’ve probably noticed, those two boxes are linked and you’re only making one change.
Secondly, lets say a particular track sounds appropriate in the mix with it’s gain slider set to -3 db (less than 0 gain) with the other tracks set to 0 on their gain sliders. What value to I enter and in which box to establish that amount gain for that track with the track gain slider set to 0 db rather than -3 db?
Sorry, I’m lost… The track adjustment is independent of the Amplify effect, and the Amplify effect will ignore the track slider setting so you could get unexpected results.
Normally, mixing is done by ear. And, note that mixing is accomplished by summation so if you are mixing two tracks that go over -6dB (50%) the mix can end-up clipped (distorted). One solution is to export-as 32-bit floating-point which can go over 0dB without clipping. Then open the new-mix and run the Amplify or Normalize effect to bring the levels down (if necessary) before exporting to your desired format.
\
- Audacity uses floating-point so it can go over 0dB “internally” without clipping. For example, you might boost the bass and push the peaks over 0dB (and Audacity will show red for potential clipping). The Amplify effect will default to a negative value and you can bring the levels down to a “safe” level. Regular WAV files, DACs (playback), and ADCs (recording) are all hard-limited to 0dB and you’ll get distortion if you go over.
And in case this went by you, Amplify and its cousin Normalize work on blue wave tips and peaks. Full stop. Different from loudness.
Peaks are a pleasure to program. Go ripping down the show looking for the highest number. Then change it and the rest of the show depending on selection and the user settings.
LUFS and RMS are very different from that. RMS is the loudness specification of ACX Audiobooks. LUFS can be a podcast loudness specification.
Both of those demand that you analyze the character of the sound. RMS is the area under the curve (waves) which someone determined works out to about loudness. It’s calculus. A real knee-slapper. Lots different than just looking for the highest number. LUFS is even worse. That one takes into account the behavior of the human ear. Why do babies screaming on a jet bother you so much? They’re not that much louder than the actual jet. That’s LUFS.
And just when you thought it was safe to go back in the water, you can have loudness and peaks conflict.
Koz