Ubuntu's sound preferences dialog (the one you get to by clicking on the little speaker icon in the indicator applet) has a couple notches on the slider, one marked "Unamplified" and one marked "100%". And the thing doesn't stop at 100% either.

enter image description here

So what does 100% mean if it doesn't mean either "the signal without amplification" or "as loud as I can make it"?

Where do I want it set if I want the strongest signal sent to my speakers without danger of clipping?

  • As far as I can tell, it doesn't mean anything. On USB Audio devices, if you watch the slider in alsamixer, it shows that these values just map to totally arbitrary dB levels. Every signal is amplified in some way, so "Unamplified" is pretty meaningless. – endolith Jan 19 '18 at 13:07

You are seeing this because your sound card supports amplification beyond the normal range of the actual volume. Unamplified is the normal maximum, the next marker (100%) represents the maximum amplification that your sound card supports (ie how much your sound card can amplify sound on it's own), and the highest one (the unmarked end of the slider) is the amplification that is available from pulseaudio (on top of what your sound card supports).

The safest is Unamplified%, but 100% (the second marker) might also be safe depending on the volume of what you are playing and your speaker quality. If you are playing very low volume audio files, and you don't want to use normalization, you can use these features to your advantage.

  • Hmm, the labels you're using don't match up with what I'm seeing. In the screenshot I posted, there's a marker for "unamplified" which is to the left of (lower than) the marker for "100%", and there's no marker higher than "100%", only the unlabelled high side of the slider. – keturn Jan 19 '11 at 4:32
  • oh sorry, the way your screenshot looks it seemed as if unamplified is 100%, which is the case with some cards, I'll fix my answer :) – RolandiXor Jan 19 '11 at 14:52
  • okay I fixed my answer now :) – RolandiXor Jan 19 '11 at 14:55
  • 1
    Ok, thanks for the update. Is this documented anywhere? I'd never seen anything like this in previous mixers (alsamixer, etc). – keturn Jan 20 '11 at 16:09
  • I'm not quite sure if it is documented, I know about it from experience :) - having used many computers under ubuntu with vary underlying hardware, I was able to learn how it works. – RolandiXor Jan 20 '11 at 17:05

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