[alsa-devel] RME HDSP9632, mute headphones

[Matthew Robbetts]

On 11 Oct 2010, at 06:32, Florian Faber <faber at faberman.de> wrote:

> On 10/10/10 18:45, Matthew Robbetts wrote:
> 
>> I've just acquired myself a HDSP9632 and noticed what I think is a
>> missing feature from the drivers (compared to Windows, at least): the
>> ability to set the headphones to "mute", in addition to -6dB and -12dB
>> of gain. I would find this feature useful.
>> 
>> Is there a reason it is missing or has it just been overlooked? Or,
>> alternatively, am I doing something stupid?
> 
> This has nothing to do with the driver. You set the headphone volume
> with hdspmixer, like you would do with TotalMix on Windows/Mac.
> 

Hi Flo,

Of course, you can adjust the volume digitally (though since hdspmixer overwrites all your routing every time you open it, it's a bit annoying to use). However, the card appears to have a dedicated a analogue gain stage just for the headphones. It's not a full PGA, but can be set to 0db, -6db, -12dB and mute - under windows. The ALSA driver only gives the first 3 options as controls. 

I had a quick look in the code, and it seems there's a 2-bit field in the 9632 control register for controlling this. Sounds neat, as we have 4 possible values. Can anyone confirm that the unused value (0x10, IIRC) in the ALSA driver is used to mute the headphones?

Regards,
Matt