[linux-audio-user] What are Master, PCM and AC97?

Christoph Eckert mchristoph.eckert at t-online.de
Sat Feb 12 18:22:20 EST 2005

> When I open KMix, the KDE Mixer, I can change the volume of
> both "Master" and "PCM" which both change the music volume.

PCM controls the volume of all sound generating programs, 
which means which volume is put *to* the mixer.

Master controls at which level the audio data *in* the mixer 
leaves the mixer to the outputs.

Therefore, PCM controls the in gain, while master controls the 
out gain.

Besides PCM, there are other sources like CD and so on. So, 
the mixer inputs allow you to adjust the mixing of the 
different sources, while master sets the volume of the 
general output.

> I can also control the volume of "AC97" but that has no
> effect while playing music.

I didn't ever need this, so I do not know for what it is :) .

Best regards


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