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