VLC Equalizer increase sound quality

[Calthax]

Can enabling equalizer and setting preamp from 12 dB to (9 dB with single pass/10.5dB with 2 pass) with default/flat equalizer settings increase sound quality

[Lotesdelere]

Any equalizer will not increase the quality, flat or not.

It will just modify the source spectrum to adapt it to a specific system and a specific room.
This has nothing to do with the quality of the source.

In your case you want a higher volume. What about you just turn up the volume knob of your amp/speakers ?