3.5mm Audio Jack - opencardev/crankshaft GitHub Wiki

Please note: since the original Pi B+ version, the 3.5mm jack on the Raspberry Pi has not been dedicated to audio alone. The jack is a 4-pole (3 rings or tip, ring, ring, sleeve - TRRS) audio / video jack. This is explained in detail at the Raspberry Pi Spy site.

If using the Raspberry Pi 3.5mm jack to output sound into your car's aux (auxiliary) input socket (if your car has one), sound quality can be improved by adding the following line to your boot/config.txt file:

audio_pwm_mode=2

This enables the 7bit, 781kHz audio driver released in 2016. Compared to the much-maligned original 11bit, 48kHz driver you should notice the difference ;)

For users who want audio via 3.5mm jack and are using hdmi screen, sometimes the audio has trouble to be output on the jack. By adding the following line to your boot/config.txt file, this issue may be solved:

dtparam=audio=on

audio_pwm_mode=2

hdmi_ignore_edid_audio=1

disable_audio_dither=1

More details are available on the Raspberry Pi forum.