Bug 151297

Version:            (using KDE KDE 3.5.7)
Installed from:    Fedora RPMs
OS:                Linux

On many soundcards 100% of master and 100% of PCM results in the soundcard outputting more than the 'line level' that amplifiers or amplified speakers are expecting, resulting in distorted sound. The usual workaround for this problem is to 'turn the mixer values down a bit'.

Later versions of alsamixer (e.g. 1.0.14) show a 'dB gain=' value for the selected slider. In my case (VIA 8237) master of 100% results in +-0db and PCM of 74% results in +-0db. Push the PCM any higher and the gain goes above zero and sound gets distorted.

KMix should add an option to scale the sliders relative to zero gain; 100% for all sliders would be whatever value results in a gain of 0. With this option selected the user could have all his sliders at max and get a loud clear sound with no distortion, there is no way to increase the soundcard's output gain above 0/'line level'.

Another option might be to allow the user to slide the slider above 100%, if they have some reason to want to boost the signal beyond line level - e.g. for poorly recorded music. In this case scaling the values to match the gain makes it obvious to the user that they are pre-amplifying their soundcard output to be higher than 100% so they can expect distortion and will turn it back down to 100% for normal use.

Personally I don't think I'd use the second option, but I guess there are some people who might.