[alsa-devel] dB, dB and more dB....

John Rigg aldev at sound-man.co.uk
Tue Apr 15 15:01:29 CEST 2008

On Mon, Apr 14, 2008 at 05:50:33PM -0700, Tom Watson wrote:
> I find all of this an interesting discussion, and it looks like:
> 1)  People want to hear some output.
> 2)  "Pro" people don't want to blow up speakers.

Yes. I'd add to number 2: "pro" people don't want to hear any
output until they set the relevant control to give output.

> It seems that all of us have differing ideas on "what to expect" when it comes
> to audio interfaces.  Twenty years ago, these problems really didn't exist,
> since computer audio was in its infancy, but now audio is everywhere, and it
> muct be accounted for.  Alsa's implementation of having audio MUTED on
> initialization (startup) is a good one, and many distributions have init
> scripts that take over from there, restoring old values.  While not ideal (just
> set the audio to where I want it!), it is about the best we can do.

Doing it any other way would in fact render "pro" hardware unusable.

> The "pro" guy who doesn't want to blow up his speakers, I can only offer a
> suggestion.  What do you do when plugging in and out "normal" audio equipment. 
> Most of the time I turn down the level control since my big fat fingers will
> end up touching the tip/ring of the audio connector and LOTS of hum results. 
> If you don't do this, you may have a PEBKAC problem which I (or any other
> developer) can solve.

If a software mixer starts up unmuted it's too late. With hardware you have
the option of pressing a mute button or turning down a gain control before
turning power on. A software mixer needs to be running before you
can alter the default values.

> I think we are all chasing a problem that really doesn't exist.
> As for dB, some people refer to 0dB as "full scale".  Some refer to it as 0 VU.
>  Some make it out to be 1-v p-p.  Go figure.  The biggest problem is that crazy
> people think "louder" is better.  It isn't!

The main misunderstanding appears to be the fact
that dB settings in a mixer refer to gain, not level.


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