"Amplify" effect

[Crosscloud]

macos is Mohave ver. 10.14.1 and Audacity ver. is 2.3.3. I understand that the relative mix volumes of multiple tracks can be tested by altering volumes of different tracks using the volume sliders in the track control panels. So I have determined one track needs to be raised by 6db relative to all other tracks. In the "Amplify" effect adjustment controls there are two dialog boxes in which db levels can be adjusted, namely "Amplification" (db): and "New Peak Amplitude " (db). There is also an "Allow clipping" checkbox. After I select the track I wish to raise by 6 db, what should be the values entered in each of these boxes and should clipping checkbox be checked? I've read through the manuals and many threads in this forum but I don't understand how to accomplish what should be a fairly simple task. The relationship to 0 db, etc. I find confusing.

[steve]

I have determined one track needs to be raised by 6db relative to all other tracks.

The key word there is "relative".
dB levels are always "relative".

Another way to increase one track +6dB relative to all other tracks is to keep that track the same and lower all other track -6dB.

Another way to increase one track +6dB relative to all other tracks is to raise that track by +2dB and lower all others by -4dB.

In each case, you are making that one track +6dB relative to the other tracks.


Normally you should leave "Allow clipping" unchecked (off). This is the default and it is extremely rare that anyone should need to change it.

So your first option is to increase one track by +6dB
"Amplification (dB): +6"

but if "allow clipping" is off, the effect may not allow you to amplify by that amount. However, you can still amplify all other tracks by -6dB (negative 6).
This is like using a mixing desk - you can't keep pushing levels up and up, sometimes you need to pull levels down.

[DVDdoug]

The peak does not correspond well with perceived loudness. So for example, if you amplify/normalize all of your songs/tracks to 0dB (peak) some will still be louder than others.

0dB is the "digital maximum". Audacity itself can internally-temporarily go over 0dB but analog-to-digital converters (recording), digital to-analog converters (playback), CDs and regular WAV files are all hard-limited to 0dB and you'll get clipping (distorted flat-topped waves) if you "try" to go over.

If you amplify by +6dB that's a doubling of the signal amplitude, or a doubling of the electrical signal which results in 4 times the power (Watts). If you "amplify" by -6dB, that's actually attenuation (not amplification) and again that's a factor of two, so half of whatever you had before.

If you amplify to -6dB by setting "New Peak Amplitude", the level will be amplified or attenuated as necessary to make the peaks -6dB. If you do the same thing again, nothing will happen.

You can't amplify to +6dB unless you allow clipping. And, the file/data won't actually be clipped until you export, or the DAC (digital-to-analog converter) will clip if you play at full volume.

I understand that the relative mix volumes of multiple tracks can be tested by altering volumes of different tracks using the volume sliders in the track control panels.

Normally, mixing is done by-ear. Note that mixing is done by summation* so it's not unusual to get (potential) clipping. The simplest solution is to export-as floating-point WAV (which is not limited to 0dB). Then re-import the mixed file and use the Amplify or Normalize effect to bring the levels down to a "safe" level. Then export again to your desired format.

"Allow clipping" only applies to the individual tracks so even if you don't allow clipping, the mix can still be (potentially) clipped.

More advanced mixing software will also have a master volume/level control (like a "real" hardware mixer) and meters for every track plus a meter for the mix. But still there is often an additional "mastering" step after mixing & rendering (exporting).





* Analog mixers are built around a summing amplifier but there is always a master volume control so it usually ends-up more like an average or weighted average.

[Crosscloud]

Steve and DVDoug, Thanks for the replies. Steve, I realized the relationships of which you speak. I'm going to be very specific here now. I have a Hammond organ track and a Mellotron strings track. To my ear, the relative amplification factors (using the volume sliders in the two track control panels) are: Organ +4 db and Mellotron strings -2 db for an overall 6 db difference in levels. What is the easiest way to accomplish these two changes in level? (Note: I'm primarily an old school, analog, keyboardist and have only been messing with home recording and Audacity since I aged out of public performing a couple years back. Please excuse my lack of expertise in audio recording)

[steve]

To my ear, the relative amplification factors (using the volume sliders in the two track control panels) are: Organ +4 db and Mellotron strings -2 db for an overall 6 db difference in levels. What is the easiest way to accomplish these two changes in level? (Note: I'm primarily an old school, analog, keyboardist and have only been messing with home recording and Audacity since I aged out of public performing a couple years back.

Probably the easiest way is to use the Mixer Board: https://manual.audacityteam.org/man/mixer_board.html

When using the Mixer Board, keep an eye on Audacity's playback meter. It is essential that the mix level remains under 0 dB.

Note that the meter may be resized (up to full window width) by dragging the right edge of the meter (drag the left edge to reposition the meter)
See here for more info about toolbars: https://manual.audacityteam.org/man/too ... rview.html