[alsa-devel] [PATCH] New quirk for USB DAC 08bb:2704

Omari Stephens xsdg at xsdg.org
Sat Feb 12 23:53:25 CET 2011

Howdy, all

I have one of these:

It's got one of these USB DACs inside
ID 08bb:2704 Texas Instruments Japan

The DAC has a single mixer control, Master, which allows you to adjust 
volume and mute/unmute.  The fun thing is that the volume adjustment has 
no effect whatsoever.  On machines running pulse, this means that output 
will be at 0dB pretty much all the time.  (Of course, this is true of 
non-pulse machines also).

The attached patch disables the Master control, which causes pulse to 
control levels entirely in software, as it should for this device.

The main downside to this patch is that, while the volume part of the 
Master control is non-functional, the mute/unmute aspect does work as 
expected.  I couldn't figure out how to change the Master control to 
just a mute/unmute control, but if someone has suggestions on what to 
do, that'd be appreciated.  Judging by the comments in the code (and 
contrary to what I wrote in the map comment), I presume the mute/unmute 
control is the only reason why 08bb:2702 isn't doing this same thing.

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