[alsa-devel] What does 0dB refer to? (Logitech USB Speakers)

Rene Herman rene.herman at keyaccess.nl
Mon Apr 14 19:22:59 CEST 2008

On 14-04-08 19:00, Lennart Poettering wrote:

> On Sat, 12.04.08 21:32, Rene Herman (rene.herman at keyaccess.nl) wrote:

>> If we add in ISA cards, it's not a very generic assumption at least. For 
>> example on my cs4236, "master" is -94,5 to +12 dB with 0dB at "87" in the 
>> integer scale.
>> It's a "Master Digital Gain" -- not sure what that "digital" implies as it 
>> very much seems to be positioend in the post output mixer analog path...
> Maybe the driver should add an internal offset to the dB scale, to
> guarantee that 0dB is max, instead of just copying the hw specs?

No, really quite definitely not. 0 dB means no attenuation of amplification. 
How loud that actually ends up is very much dependent on what's _behind_ 
your line-out.

In this specific example, the cs4236 master is split in a digital part -60 
dB to 0 and an anlog -34,5 to +12. I most certainly want "0 dB" to mean no 
analog amplification (nor (digital) attenuation, but the analog is what I 
want to know) is being done.

And "Reply-To" from my previous message should be "Mail-Followup-To". Please 
kill that.


More information about the Alsa-devel mailing list