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

Rene Herman rene.herman at keyaccess.nl
Wed Apr 16 17:19:15 CEST 2008

On 16-04-08 16:29, Rene Herman wrote:

> On 15-04-08 16:33, Rene Herman wrote:
>> mute/minimal. Bit of a maintenance chore, and the usefulness depends 
>> on how much level variation there actually is generally. Are we in 
>> essence only talking about Lennart's buggy USB crap or is this more 
>> involved?
> On that note, I just acquired an Audigy 2 (SB0240) that I'm testing with 
> and now that I'm paying attention to it due to this thread -- its 0 dB 
> setting is very significantly louder (with everything behind the 
> line-out constant ofcourse) than the 0 dB setting on my TerraTec DMX.
> James, I believe you are the emu10k1 person? Data:
> TerraTec DMX = ESS Canyon3D (ES1970MS-3D) + Sigmatel STAC9704T
> Creative Audigy 2 (SB0240) = Creative CA0102-ICT + Sigmatel STAC9721T (+ 
> Crystal CS4382-KQ which seems to provide digital attenuation as well)
> At 0 dB master the Audigy 2 is much louder than the DMX is and audibly 
> distorts. Judging by hearing, keeping the master at -16 dB (60 in the 
> integer scale) gets things about the same. Was that scale provided by 
> datasheet or just guessed? Especially the distortion would seem to 
> indicate that something is actually doing analogue amplification at the 
> 0 dB ALSA setting...

Expanding, with the 'Line' control at 0 dB (74 integer) and 'Analog Mix' at 
0 dB (100 integer) everything does sound right with both 'Master Capture' 
and 'Master' at  full, and too faint with 'Master' at -16 dB. I guess this 
indicates that it's something at the DSP side only? (sort of loosing my way 
in this bewildering array of controls so if I need to be guided to possibly 
say sensible things -- please do)


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