Speaker Hum on Idle (AMD Ryzen / Realtek ALC1220)

External speakers connected via the motherboard’s analog audio jack emit a low-level hum/buzz a few seconds after audio stops playing. Starting playback again briefly silences the hum, then it returns once playback stops.

Cause

The Linux snd_hda_intel driver has codec autosuspend enabled by default. On my desktop, the default power-save timeout was 10 seconds:

$ cat /sys/module/snd_hda_intel/parameters/power_save
10

When no audio stream is active, the HDA codec is put into D3. The resulting power-down/queue-reset on the codec outputs a DC offset and pop that the external amp picks up as hum.

Fix

Disable codec autosuspend for snd_hda_intel and disable controller power-save.

1. Persistent (modprobe.d)

Create /etc/modprobe.d/snd_hda_intel.conf:

options snd_hda_intel power_save=0 power_save_controller=N

Reboot, or reload the module:

sudo modprobe -r snd_hda_intel
sudo modprobe snd_hda_intel

2. Immediate (runtime, no reboot)

echo 0 | sudo tee /sys/module/snd_hda_intel/parameters/power_save
for d in /sys/bus/pci/devices/*/power/control; do
  [ "$(cat ${d%/power/control}/class 2>/dev/null)" = "0x040300" ] && echo on | sudo tee "$d" >/dev/null
done

Verification

$ cat /sys/module/snd_hda_intel/parameters/power_save
0

Stop playback. The hum should no longer return after the idle interval.