In most cases the balance is shifted to the right. Adjustment done in pavucontrol works until the tune ends, and gets reset as soon as the next one starts. Does anyone have an idea on how to make balance settings permanent for a certain source (in this case, Firefox)?
pactl -- set-sink-volume @DEFAULT_SINK@ +5dB does what you need?
This changes volume for both channels.
This is quite interesting, but I’m not even touching the volume setting.