I am using an Acer Aspire A115-31 laptop. When running newer kernel versions, sound played through headphones is distorted, but when running older versions, it is not.
Kernel version: Linux version 6.12.5 (user@hostname) (gcc (Debian 14.2.0-8) 14.2.0, GNU ld (GNU Binutils for Debian) 2.43.50.20241210) #1 SMP PREEMPT_DYNAMIC Sun Dec 15 05:09:16 IST 2024 Operating System: Debian GNU/Linux trixie/sid
No special actions are needed to reproduce the issue. The sound is distorted all the time, and it doesn't depend on anything besides using an affected kernel version.
It seems to be caused by commit 34ab5bbc6e82214d7f7393eba26d164b303ebb4e (ALSA: hda/realtek - Add Headset Mic supported Acer NB platform). Indeed, if I remove the entry that this commit adds, the issue disappears.
lspci output for the device in question:
00:0e.0 Multimedia audio controller [0401]: Intel Corporation Celeron/Pentium Silver Processor High Definition Audio [8086:3198] (rev 06) Subsystem: Acer Incorporated [ALI] Device [1025:1360] Flags: bus master, fast devsel, latency 0, IRQ 130 Memory at a1214000 (64-bit, non-prefetchable) [size=16K] Memory at a1000000 (64-bit, non-prefetchable) [size=1M] Capabilities: [50] Power Management version 3 Capabilities: [80] Vendor Specific Information: Len=14 <?> Capabilities: [60] MSI: Enable+ Count=1/1 Maskable- 64bit+ Capabilities: [70] Express Root Complex Integrated Endpoint, IntMsgNum 0 Kernel driver in use: snd_hda_intel Kernel modules: snd_hda_intel, snd_soc_avs, snd_sof_pci_intel_apl