[alsa-devel] Disable DAPM for click avoidance ?

[Mark Brown]

On Fri, Mar 23, 2018 at 05:23:23PM +0100, Ricard Wanderlof wrote:

> Yes, there is a bit for setting the output amplifier in power save mode, 
> which is handled as a PM bit in the driver. The specs aren't that bad, the 
> worst case SNR is 80 dB, with 97 dB typical. The good thing about using 
> this bit is that when the output amplifier is in power save mode, there is 
> actually a high impedance connection to VMID, so that as long as the 
> device is powered on properly, the outputs take a while to reach VMID 
> depending on the value of the DC blocking cap on the output, and the slow 
> ramp also avoids clicks when powering on the device (and we don't start an 
> output stream until quite a while after powering on the system).

That feature sounds normal for such old devices, you should be using
that rather than ramping VMID from ground every time you want to start
and stop playback.  There's a number of very old drivers doing something
similar, grepping around will probably show something.
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