From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jarkko Nikula <jhnikula@gmail.com>
Subject: Re: [PATCH -next] ASoC: pandora: Add DAC regulator
 support
Date: Sun, 7 Feb 2010 11:07:32 +0200
Message-ID: <20100207110732.9279b77a.jhnikula@gmail.com>
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To: Grazvydas Ignotas <notasas@gmail.com>
Cc: alsa-devel@alsa-project.org, Mark Brown <broonie@opensource.wolfsonmicro.com>, Liam Girdwood <lrg@slimlogic.co.uk>
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On Sat, 6 Feb 2010 19:33:08 +0200
Grazvydas Ignotas <notasas@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


-- 
Jarkko