A DBX box ca. 1975 sound expander. In college, listening exclusively to rock, albeit good rock, but no need for the expander! It did make a big difference, however, on Thick As A Brick, but that alone did not justify the expense. Wonder if there are products like that now. Probably worked great on classical.
Anyway, took it to the dorm for an audition, my buddies still say "I hear the difference" as they continue to make fun of me in my early pursuit of perfect audio. Wasn't so bad: Tandberg 1055, Dual 1215S, Shure M55E?, ADS 710, B&0 Beogram 3000.
biz