The sound card disconnects when the volume is raised by 70% or more

[tomoyan596]

Hello.

If you turn up the volume while playing music, there will be no sound when it exceeds 70%, and alsamixer will be disconnected from the sound card. I'm not sure what's going on with the sound SoC.

Nothing is written in syslog either.

The music can be played again when the system is restarted.

Is there a way to see what's going on? Is there any improvement other than rebooting the system?

Thank you.

[tomoyan596]

Something like this is happening😅 https://twitter.com/tomoyan596/status/1344110168489906177

[tomoyan596]

Hello.

This is a very good report. As a result of trial and error, I found a way to avoid the phenomenon. Under Clock & Voltage on the Raspberry Pi Zero WH no longer disconnects when the sound card volume is maximized. What can be said from this is that under the standard state of Raspberry Pi Zero WH, the power supply to the HAT is insufficient, causing the phenomenon.

The setting method is listed below.

Thank you.

https://twitter.com/tomoyan596/status/1344533198219296768

$ sudo nano /boot/config.txt arm_freq=700 over_voltage=-7

$ cat /proc/cpuinfo processor: 0 model name: ARMv6-compatible ... BogoMIPS: 997.08

$ sudo reboot

↓

$ cat /proc/cpuinfo processor: 0 model name: ARMv6-compatible ... BogoMIPS: 697.95

Maximize the volume of your sound card.

[shawaj]

@tomoyan596 it seems that this relates to the D.Limit threshold in alsamixer / MA12070P chip - see datasheet page 20 https://www.infineon.com/dgdl/Infineon-MA12070P-DS-v01_00-EN.pdf?fileId=5546d46264a8de7e0164b761f2f261e4

I am not 100% certain, but I think this is intended functionality to protect the attached speakers.

[AMuszkat]

@tomoyan596,

As @shawaj is mentioning this is correct. The merus-amp hat board includes a DC-DC boost converter which has a current input limit to protect from over current while using the Raspberry pi official power supply (in this case around 4A peak). Depending on your speaker impedance when getting close to the max volume this protection will trigger, desconneting and muting the board. This is beahvour is expected.

[tomoyan596]

@shawaj, @AMuszkat,

Thank you for your kind answers and advice. By adjusting the D.Limit threshold of alsamixer that @shawaj taught me, I was able to prevent the board from being disconnected by volume operation.

It was a product that just arrived the other day, and I first checked the operation. There is no problem in operation, so read the data sheet etc. carefully.

I am surprised that the audio processor is highly functional. It's hard to understand what's happening because it's not recorded in dmesg or syslog, but I'll do my best.

Thank you everyone.