[alsa-devel] [PATCH] ALSA: ca0106: Disable IZD on SB0570 DAC to fix audio pops

[Takashi Iwai]

On Sun, 28 Oct 2018 17:55:12 +0100,
Alex Stanoev wrote:
> 
> The Creative Audigy SE (SB0570) card currently exhibits an audible pop
> whenever playback is stopped or resumed, or during silent periods of an
> audio stream. Initialise the IZD bit to the 0 to eliminate these pops.
> 
> The Infinite Zero Detection (IZD) feature on the DAC causes the output
> to be shunted to Vcap after 2048 samples of silence. This discharges the
> AC coupling capacitor through the output and causes the aforementioned
> pop/click noise.
> 
> The behaviour of the IZD bit is described on page 15 of the WM8768GEDS
> datasheet: "With IZD=1, applying MUTE for 1024 consecutive input samples
> will cause all outputs to be connected directly to VCAP. This also
> happens if 2048 consecutive zero input samples are applied to all 6
> channels, and IZD=0. It will be removed as soon as any channel receives
> a non-zero input". I believe the second sentence might be referring to
> IZD=1 instead of IZD=0 given the observed behaviour of the card.
> 
> This change should make the DAC initialisation consistent with
> Creative's Windows driver, as this popping persists when initialising
> the card in Linux and soft rebooting into Windows, but is not present on
> a cold boot to Windows.
> 
> Signed-off-by: Alex Stanoev <alex at astanoev.com>

Applied (with Cc to stable) now.  Thanks.


Takashi