Hello Yann,
MIX gain:

For the detailed description of the AVC gain please refer to the page 23 in the datasheet.
When the measured audio level is below threshold, the AVC can apply a maximum gain of up to 12 dB. The maximum gain can be selected, either 0, 6, or 12 dB. When the maximum gain is set to 0 dB the AVC acts as a limiter. In this case the AVC only takes effect when the signal level is above the threshold.
Bass enhancement-please refer to page 21.

Tone control

With Best Regards,
Jozef