Every time I review a digital-to-analog converter, my memory drifts to the spring of 1983, when the first Compact Discs arrived at Tower Records in New York City. They appeared in the opera section. Sitting next to big, thick boxed sets of opera LPs, these new discs looked truly compact. A few months later, boxed sets of popular opera LPs, in almost untouched condition, began selling in the Tower Annex for $1/disc.