Re: [Alsa-user] Recording and mixer levels

[Bill U. <un...@ph...>]

On Thu, 8 Jul 2004, lee azzarello wrote:

> AFAIK this is just the way this driver functions. It's not exactly a
> "high performance" sound card, although I use it every day to record
> and broadcast a daily radio show so it's doing something right.
> Visit: 
> http://www.archive.org/audio/collection.php?collection=democracy_now
> for some audio examples. 

Yes, this seems to be true in general. The LineIn MicIn sliders control
only how much of the input is delivered directly by the soundcard itself
to the output. That is what these sliders "mean". The amplitude of the
signal delivered from the sound card to the computer is controlled by
other sliders. Why they are given the names they are? Who knows. Some
historical artifact I suspect. 

> 
> On Thu, 08 Jul 2004 16:48:14 +0800, Daniel Piccoli
> <d.p...@mu...> wrote:
> > Hi,
> > 
> > I have tried to do some recording in Linux, using audacity with moderate
> > success. I have connected my FM tuner to the line in socket at the back
> > of my SB Live DE. This of course uses the emu10k1 drivers.
> > 
> > I have also selected line-in as the source in audacity. I have
> > experimented with both alsa-mixer, and the regular gnome-mixer (which
> > shows oss emulated mixer settings) to adjust levels to avoid clipping
> > etc.
> > 
> > I have found that adjusting "Line In" has no influence on the recording
> > level (but it does change the level of what I can hear through my
> > headphones). The recording level can only be adjusted using "capture" in
> > the alsa-mixer, and "in-gain" in the OSS mixer.
> > 
> > This is a bit disturbing because the alsa recording quality guide
> > advises against the use of input gain by the soundcard. It instead says
> > to boost the source before it reaches the soundcard.

It is always better to make sure that the input equals the range that
the card can handle. electronic and digitial noise are something that no
gain control can control. 

Note that many sound cards (esp cheap ones) start to become non-linear
well befor they clip. 
If you want you can try using 
http://www.theory.physics.ubc.ca/soundcard/soundcard.html
to test your soundcard and to try adjusting the input levels to the
point where they start distorting (noise going up).

This requires that the sound card operate in duplex mode. 
> > 
> > Has anyone else experienced this. Is the mixer misleading?

Probably yes.