I borrowed a dBx in college, a trial from Stereo Sound (I believe) on Rte 347 in Long Island. There was a guy Elliot there who later was in a Manhattan store…but I digress.
The best thing to listen to at the time was Thick As A Brick, because of the dynamic nature of that recording. Otherwise, for straight forward rock and roll there wasn't much difference to my ears (as I recall).
Anyway, I dragged everyone into my dorm room to listen to the hookup, with and without the dBx. Granted, these were not specifically encoded disks, just regular records that were expanded. I asked everyone if they could hear the difference, and eventually returned the unit.
For a couple of college years afterward, people listening to the stereo would nod their heads knowingly and mockingly say "I hear the difference." Never lived that experiment down!
Paul