[alsa-devel] Verifying mixer dB data/Invalid dB data from USB cards, especially Aureon 5.1 MkII

[James Courtier-Dutton]

On 16 February 2010 23:56, Lennart Poettering <mznyfn at 0pointer.de> wrote:
>
> The reason I was asking how Jaroslav chose the 0dB position for his
> measurements was purely because I wanted to do my own measurements for
> that Aureon card. The dbmeasure tool I wrote for stuff like that puts
> 0dB at max amplification, however Jaroslav didn't, so I was wondering
> how he chose 0dB then.
>
> Lennart
>

I think the digital side is clear. So I will not go into that.

I think we need to separate the analogue side into a number of categories:
1) Standard consumer line-out levels.
2) Standard pro line-out levels.
3) Consumer line-in levels.
4) Pro line-in levels.
5) Consumer mic levels.
6) Pro mic levels.
7) Consumer speaker levels.
8) Pro speaker levels.

On the analogue side, I believe the 0dB gain point is intended to be
the point at which one can be fairly sure that the distortion will be
low for a sensible full scale input.
I think we can get better definition on items 1 to 4.
To this end, I think ALSA needs a new control type so the user can set
what line out voltages will occur using standard full scale digital
inputs.
http://en.wikipedia.org/wiki/Decibel