https://forum.audiogon.com/discussions/is-deqx-a-game-changer?
And their website is worth visiting as well, of course:
http://www.deqx.com/
I use their top of the line HDP-5 model, which serves as my preamp as well as providing speaker and room calibrations/corrections. (And yes, to answer your question those can be switched off or on at the touch of a button on either the remote or the front panel).
My own experiences getting it dialed in, which at my slow and methodical pace extended over about 6 months, are reported in the above mentioned thread in posts between 5-16-2015 and 12-2-2015.
Best regards,
-- Al