[alsa-devel] [PATCH -next] ASoC: pandora: Add DAC regulator support

Jarkko Nikula jhnikula at gmail.com
Sun Feb 7 10:07:32 CET 2010

On Sat, 6 Feb 2010 19:33:08 +0200
Grazvydas Ignotas <notasas at gmail.com> wrote:

> It's on powerdown, there is a faint pop. It appears its the amp (final
> part in the path), I tried to toggle it while playing /dev/zero
> manually and it always pops on powerdown. On powerup there is a small
> sound cutoff too, probably because of amp capacitors charging, but we
> decided to leave it instead of halting every sound playing program
> until the amp gets ready.
My side comment for the /dev/zero test. You may hear pops also
if /dev/zero is played as unsigned 8-bit samples on signed DAC since
then samples gets converted to maximum negative value.

So there is a difference how the /dev/zero is played. First command
below produces a pop because it's playing a pop and second produces a
pop only if HW is producing it.

aplay /dev/zero
aplay -f S16_LE /dev/zero


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