Continuous pink noise on the SGTL5000 headphone output

[nataut]

Hi all.

In my openstlinux yocto image has been included the SGTL5000 audio codec management. I have a problem. On the headphone output I heard only a continuous pink noise.

These are some information from my system:

zcat /proc/config.gz | grep SGTL
CONFIG_SND_SOC_SGTL5000=y

:~# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: STM32MP1 [i.Core STM32MP1], device 0: 4400b004.audio-controller-sgtl5000 sgtl5000-0 [4400b004.audio-controller-sgtl5000 sgtl5000-0]
Subdevices: 1/1
Subdevice #0: subdevice #0

:~# aplay -L
null
Discard all samples (playback) or generate zero samples (capture)
pulse
PulseAudio Sound Server
default
Default ALSA Output (currently PulseAudio Sound Server)
sysdefault:CARD=STM32MP1
i.Core STM32MP1, 4400b004.audio-controller-sgtl5000 sgtl5000-0
Default Audio Device

The command

:~# speaker-test -c 0 -t sine -f 2500

seems to add a "sine" signal on the output but the pink noise always remains.

The command

:~# amixer -c0 sset Headphone 0

switch-off the signal output

How can I solve the problem?

Many thanks

Regards

[nataut]

I solved the problem. The pink noise came from the "Capture" line (MIC line). I disabled the "Capture" gain with the command:

 

~# amixer -c 0 sset 'Capture' 0%

 

Now the problem is gone

Edit:

The previuos command has eliminated the headphone noise until the next reboot. After the reboot, the noise is present again, even if the 'Capture' signal level is set to 0%

  

[nataut]

I'm confused.

Sometimes the noise disappears making a simple reboot. In this condition the headphone output works fine even if the "Capture" signal level is greather than 0%. Instead, when the noise is present any command doesn't eliminates it.

Is it a hardware problem or is there some initial configuration setting to do to avoid this problem?        

[nataut]

I found the solution to my problem. The DMESG showed the following line: "Using internal LDO instead of VDDD: check ER1 erratum". Based on this indication I assumed there was a conflict between the internal and external power supplies on the VDDD pin. I disconnected the VDDD SGTL pin from the external 1.5V power supply and I connected a 0.1uF capacitor near to the VDDD SGTL pin. The problem never occurred again. I wonder why the use of the internal LDO regulator has been forced. Maybe because is it a device tree setting? What are the advantage/disvantage of using the internal LDO vs external regulator?

Regards